Patent Publication Number: US-2023160563-A9

Title: Fixtures, Power and Control Systems for Same

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This is a nonprovisional of U.S. Provisional Application No. 63/023,244, filed May 11, 2020, which is hereby incorporated by reference herein in its entirety. This application claims the benefit of priority under 35 U.S.C. 119(a) of commonly-owned P.R.C. Utility Model Applications Nos. 202021096556.2, filed Jun. 12, 2020, 202021529651.7, filed Jul. 28, 2020, 202021676898.1, filed Aug. 12, 2020, 202022130240.7, filed Sep. 24, 2020, and 202022130319.X, filed Sep. 24, 2020, P.R.C. Invention Application No. 202110043839.3, filed Jan. 13, 2021, and P.R.C. Utility Model Applications Nos. 202120090398.8, filed Jan. 13, 2021, and 202120328550.1, filed Feb. 5, 2021, all of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Deployment of fixtures in architectural environments typically involves interrelationship of fixture layout, functionality and performance control. Adapting fixture layout, functionality or performance to different environments, or to changes in the environment, can be difficult. 
     It would therefore be desirable to provide apparatus and methods for deployment of fixtures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and advantages of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG.  1    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  2    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  3    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  4    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  5    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  6    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  7    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  8    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  9    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  10    is partial view “ 10 ,” approximately identified in  FIG.  9   . 
         FIG.  11    is a partial cross-sectional view taken along lines  11 - 11  in  FIG.  10   . 
         FIG.  12    is a partial cross-sectional view taken along lines  11 - 11  and  12 - 12  in  FIG.  10   . 
         FIG.  13    is a partial cross-sectional view taken along lines  11 - 11  and  13 - 13  in  FIG.  10   . 
         FIG.  14    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  15    is a partial cross-sectional view taken along lines  15 - 15  in  FIG.  13   . 
         FIG.  16    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  17    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  18    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  19    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  20    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  21    is part of a view taken along lines  21 - 21  in  FIG.  20   . 
         FIG.  21    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  23    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  24    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  25    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  26    is part of a view taken along lines  26 ( 1 )- 26 ( 1 ) and  26 ( 2 )- 26 ( 2 ) shown in  FIG.  23   . 
         FIG.  27    is part of a view taken along lines  27 ( 1 )- 27 ( 1 ) and  27 ( 2 )- 27 ( 2 ) shown in  FIG.  23   . 
         FIG.  28    shows the apparatus shown in  FIG.  27    from a perspective that is different from that shown in  FIG.  27    when the apparatus is in a state that is different from the state shown in  FIG.  27   . 
         FIG.  29    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  30    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  31    is a partial cross-sectional view taken along lines  31 - 31  in  FIG.  30   . 
         FIG.  32    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  33    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  34    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  35    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  36    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  37    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  38    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  39    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  40    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  41    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  42    is a partial cross-sectional view taken along lines  42 - 42  in  FIG.  34   . 
         FIG.  43    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  44    is a partial cross-sectional view taken along lines  44 ( 1 )- 44 ( 1 ) and  44 ( 2 )- 44 ( 2 ) in  FIG.  37   . 
         FIG.  45    is a partial cross-sectional view taken along lines  45 - 45  in  FIG.  37   . 
         FIG.  46    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  47    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  48    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  49    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  50    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  51    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  52    is a partial cross-sectional view taken along lines  52 - 52  in  FIG.  41   . 
         FIG.  53    is a partial cross-sectional view taken along lines  53 - 53  in  FIG.  41   . 
         FIG.  54    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  55    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  56    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  57    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  58    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  59    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  60    is a partial cross-sectional view taken along lines  60 - 60  in  FIG.  44   . 
         FIG.  61    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  62    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  63    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  64    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  65    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  66    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  67    is a partial cross-sectional view taken along lines  67 - 67  in  FIG.  44   . 
         FIG.  68    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  69    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  70    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  71    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  72    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  73    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  74    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  75    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  76    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  77    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  78    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  79    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  80    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  81    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  82    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  83    shows illustrative information in accordance with principles of the invention. 
         FIG.  84    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  85    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  86    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  87    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  88    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  89    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  90    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  91    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  92    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  93    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  94    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  95    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  96    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  97    shows illustrative apparatus in accordance with principles of the invention. 
         FIG.  98    shows illustrative apparatus in accordance with principles of the invention. 
     
    
    
     Generally, the leftmost digit (e.g., “L”) of a three-digit reference numeral (e.g., “LRR”), and the two leftmost digits (e.g., “LL”) of a four-digit reference numeral (e.g., “LLRR”), identify the first figure in which a part is called-out. 
     DETAILED DESCRIPTION 
     Apparatus and methods for fixture implementations are provided. 
     The apparatus may include apparatus for controlling a fixture. The fixture may include an emitter. The emitter may include a light-emitting diode (“LED”). The fixture may include an LED circuit. The LED circuit may include an LED driver. The fixture may be configured to provide direct light to a subject. The fixture may be configured to provide indirect light to the subject. The apparatus may include one or more directly configured fixtures. The apparatus may include one or more indirectly configured fixtures. The fixture may be electronically addressable. The apparatus may include a first receptacle for receiving an input power line. The apparatus may include a second receptacle for receiving an input communication line. The apparatus may include an output power terminal. The apparatus may include an output communication terminal. The apparatus may include a microprocessor. The microprocessor may be configured to regulate power delivered at the output power terminal based on a signal received at the second receptacle. The power may be stepped down from 120-48V. The power may be stepped down to any other suitable voltage, such as 24, 12, 10, 5V, or any range or subrange therein. The microprocessor may be configured to detect a power level at the first receptacle, and regulate power delivered at the output power terminal based on the level. The microprocessor may be configured to detect a power level at the first receptacle, and regulate power delivered at the output power terminal in proportion to the level. 
     The control signal may define a group. The group may be one of multiple groups. The group may include one or more of the fixtures. The group may be electronically addressable. A user may assign a fixture to a group. Directly configured fixtures may be assigned to a first group. Indirectly configured fixtures may be assigned to a second group. 
     The apparatus may include a user interface circuit. The user interface circuit may be configured to receive a control signal. The control signal may include a control message. The message may be addressed to a fixture. The message may be addressed to a group. The message may include a FIXTURE-ON instruction. The message may include a FIXTURE OFF instruction. The message may include a DIM-LEVEL instruction. The message may include a correlated color temperature (“CCT”) value. The control signal may include any other suitable control message. The message may correspond to a fixture parameter. 
     The apparatus may transmit the message from the user interface circuit to the fixture. The apparatus may transmit the message from the user interface circuit to the group. The transmission may be over a wire. The transmission may be wireless. 
     The user interface circuit may be configured to electronically communicate with a remote device. The user interface circuit may be configured to communicate with the remote device wirelessly. The user interface circuit may be configured to communicate with the remote device over wire. The user interface circuit may be configured to communicate with the remote device in conformance with a specification part set forth in IEEE 802.3, 802.11, 802.15, 802.16 or any other suitable standard. 
     The apparatus may include a connecting-power unit. The apparatus may include a power management housing. The connecting-power unit may be disposed in the housing. 
     The user interface circuit may be disposed in the housing. 
     The user interface circuit may include an I/O panel. The panel may include a keypad. The panel may include a display. The panel may include a touch-screen. The panel may be mounted on the housing. The panel may be included in a package that is separate from the housing. The package may be wall-mountable. 
     The user interface circuit may include a PHY interface to provide control signal to output terminal. 
     The apparatus may include machine readable memory. The memory may be configured to provide instructions conforming to a control protocol. The apparatus may include a cartridge receptacle. The receptacle may accept a cartridge. The cartridge may include instructions that conform to a control protocol. The control protocol may be one of multiple control protocols. 
     The microprocessor may be configured to control the fixture based on the protocol or protocols in the cartridge. The microprocessor may be configured to control the fixture consistent with the protocol or protocols in the cartridge. 
     The apparatus may include a first photo sensor. The first photo sensor may register a spectrum of ambient light. The ambient light may include exterior light. The ambient light may include interior light. The microprocessor may be configured to coordinate a hue of the fixture with the ambient light. The hue-coordination may be based on the spectrum. The microprocessor may be configured to update the hue as the ambient light changes. The hue may be based on a combination of coordinated color temperatures. 
     The apparatus may include a second photo sensor. The second photo sensor may detect a presence of a human in a space in which the track is disposed. 
     The first and second photo sensors may be collocated. The first and second photo sensors may be integrated into a single chip. Functions of both the first and second photo sensors may be provided by a single sensor device. 
     The code may include code configured to run on the remote device. The microprocessor may be configured to transmit to the remote device layout information. The layout information may include a configuration of two or more tracks or fixtures. The layout information may include location and parameters of each fixture. The code may be configured to simulate a light scene corresponding to the layout information. 
     The apparatus may include a natural lighting and time module. The module may include a global positioning chip or take a global coordinates input. The module may include a clock. The module may use the coordinates and the clock to derive, on location, natural light availability based on geophysical data. The module may transmit the coordinates and time to a remote platform. The platform may derive the natural light availability and transmit back to the module. The module may provide available daylight for harvesting. The module may provide circadian controls for the fixture based on the natural light availability. 
     The apparatus may include a mounting track. The mounting track may support the fixture. The apparatus may include a magnet. The magnet may hold the fixture on the track. The track may include a control signal bus. The control signal bus may transmit the control signal from the microprocessor to the fixture. The track may include a power rail. The power rail may transmit power from the connected power unit to the emitter. The power rail may transmit power from the connected power unit to the actuator. The power rail may transmit the control signal from the microprocessor to the fixture. The fixture may be motorized, including, among other things, for beam angle adjustment and motion of the fixture in different directions and along different axes. 
     The track may be one of multiple tracks. The apparatus may include a track connector. The connector may include an engagement feature for each of the tracks. The engagement features may be disposed at an angle relative to each other such that the tracks are oriented at that angle with respect to each other. The angle may be fixed. The angle may be variable. The angle may be selectable from predetermined discrete angles. The connector includes 2, 3, 4, 5, 6 or more tracks. 
     The connector may include a power rail jumper. The power rail jumper may conduct power from a first track to a second track. 
     The connector may include a control signal jumper. The control signal jumper may conduct the control signal from a first track to a second track. 
     The track may include a mounting plane. The mounting plane may face downward when the track is in operation. The fixture may be mountable to the mounting plane. The mounting plane may be continuous from a first end of the track to a second end of the track. One or both of the jumpers may be disposed above the mounting plane such that the connector does not interfere with placement of a fixture in a position. The position may be near an end of a track. The position may bridge from a first track to a second track. 
     The track may include a U-channel. The U-channel may include a spine. The U-channel may include a first web that extends down from a side of the spine. The U-channel may include a second web that extends down from an opposite side of the spine. The first web may face the second web across a channel. The fixture may be disposed in the channel. 
     The connector may include a plate. The plate may be configured for insertion: in a first track, below (a) a first-track spine and (b) above a first-track control signal bus and power rail; and, in a second track, below (c) a second-track spine and (d) above a second-track control signal bus and power rail. The plate may connect a first track and a second track at their top sides. The plate may be a plate that does not intervene between butt-ends of first and second tracks. The plate may be a plate that does not interfere with placement of fixtures in the track U-channels. 
     The fixture may include an actuator. An actuator may be configured to vertically displace an emitter. An actuator may be configured to rotate the emitter about a vertical axis. An actuator may be configured to adjust an angle of latitude of the emitter relative to the vertical axis. The angle of latitude may be a pitch angle. An actuator may be configured to adjust an offset between the emitter and a lens. The offset may determine the spread of a beam emitted by the emitter. 
     An actuator may include a motor. The motor may be a stepper motor. The motor may be a servo motor. The motor may be any suitable type of motor. 
     The fixture may include a stem. The fixture may include a housing. An actuator may adjust the angle between the stem and the housing to adjust the beam latitude. An actuator may retract the housing into the track. For example, the track may include a horizontal U-channel, with open side down. An actuator may adjust the beam latitude to 0 degrees, which may be defined as straight down. Then, a second actuator may retract the housing up into the channel. A lower lip of the housing may be positioned flush with the edges of the U-channel. The lower lip may be positioned above the edges of the U-channel. A third actuator may adjust the beam angle. 
     The fixture may include a reflector. The reflector may be configured to reduce or eliminate glare experienced by an individual in a space illuminated by the fixture. The reflector may be configured to reduce or eliminate glare when the individual&#39;s field of vision encompasses the fixture. The reduction or elimination may occur only when there is no direct line of sight between the individual and a lens of the fixture. 
     The fixture may include a power cord. The power cord may suspend the fixture at a distance from the track. A first end of the power cord may be fixed to the track. A second end of the power cord may be fixed inside a housing of the fixture. The housing may include a cleat and a receptacle. As the distance decreases, the cleat may engage the cord at a higher level. Cord below the cleat may be hidden from view inside the receptacle. 
     The fixture may include a lens-adjusting ring. The ring may rotate to cause a linear displacement of the lens relative to the emitter. The ring may telescopically extend from the fixture housing. The ring may be configured to cause the displacement only when the ring is in a telescopically extended configuration. The rotation of the ring or other adjusting of the lens or the lens holder in the fixture may cause a change in the angle of the beam emitted by the emitter. 
     The apparatus may include a beacon detector. The beacon detector may include an array of detectors. The array may be configured to provide optical intensities that can be used to triangulate to the 3-D location of a beacon. The microprocessor may perform the triangulation. A satellite processor mounted on the track may perform the triangulation. The detector may detect spatial coordinates of the optical beacon. The detector may detect a strength of the beacon. The detector may transmit the coordinates to the microprocessor. The detector may transmit the strength to the microprocessor. The microprocessor may adjust a direction of the fixture beam to a location relative to the beacon. The microprocessor may adjust a fixture parameter in response to the beacon location. The memory may store different relative target attitudes for different fixtures to create a predetermined light pattern relative to the beacon. 
     The apparatus may include a light tape. The light tape may be mountable on a surface of the track. The surface may face up from the track. The surface may face laterally away from the track. The tape may support the fixture. The tape may be mounted to the track by a clip. The tape may include a tape power rail. The tape may include a tape control signal bus. The apparatus may include a track-to-tape connector. The track-to-tape connector may connect the track power rail to the tape power rail. The track-to-tape connector may connect the track control signal bus to the tape control signal bus. 
     The tape may include sections. The sections may be defined by break-away connections. The break-away connections may be configured to enable a user to obtain tape of different preselected lengths. The tape power rail and tape control signal bus of a section may be configured to operate after the section is separated from an adjacent section. 
     The apparatus may include, and the methods may involve, one or more features such as a multi-protocol fixture control; a mechanical interconnection; beam spread control, beam direction control; positioning a fixture within a fixture support; fixture height adjustment; lens ring adjustability; fixture release from a fixture support; fixture operational targeting; and wired fixture deployment at a distance. Table 1 lists illustrative fixtures. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Illustrative fixtures. 
               
               
                 Illustrative fixtures 
               
               
                   
               
             
            
               
                 Light 
               
               
                 Fan 
               
               
                 Audio speaker 
               
               
                 Audio/Video projector 
               
               
                 Camera 
               
               
                 Detector/Sensor 
               
               
                 Range sensor 
               
               
                 Temperature sensor 
               
               
                 Motion sensor 
               
               
                 Occupancy sensor 
               
               
                 Visible light sensor 
               
               
                 Inertia sensor 
               
               
                 Spectral energy sensor 
               
               
                 Other suitable fixtures 
               
               
                   
               
            
           
         
       
     
     The fixture may include one or more devices. Table 2 lists illustrative devices. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Illustrative devices. 
               
               
                 Illustrative devices 
               
               
                   
               
             
            
               
                 LED emitter 
               
               
                 Switch 
               
               
                 Electro-acoustic transducer 
               
               
                 Video display 
               
               
                 Microphone 
               
               
                 Motor 
               
               
                 Linear actuator 
               
               
                 Antenna 
               
               
                 RF transmitter 
               
               
                 RF receiver 
               
               
                 Transponder 
               
               
                 Detector 
               
               
                 Sensor 
               
               
                 Other suitable devices 
               
               
                   
               
            
           
         
       
     
     The fixture may be characterized by one or more fixture parameters. Table 3 lists illustrative fixture parameters. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Illustrative fixture parameters. 
               
            
           
           
               
               
            
               
                 Illustrative fixture parameters 
                 Illustrative values, scale increments 
               
               
                   
               
               
                 Vertical displacement from track 
                   
               
               
                 Horizontal displacement from reference point 
                   
               
               
                 (e.g., end, middle, adjacent light fixture, other 
                   
               
               
                 reference point) 
                   
               
               
                 Beam pitch relative to vertical axis 
                   
               
               
                 Beam pan angle about vertical axis 
                   
               
               
                 On/Off 
                 Values: on, off 
               
               
                 Dimming curve mode 
                 Values: linear, logarithmic. 
               
               
                 Soft on fade rate 
                 scale = 1 ms. 
               
               
                 Fade to black rate 
                 scale = 1 ms. 
               
               
                 Initial status level 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 luminance level 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Color temperature mix level 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Dimming channel (RED) 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Dimming channel (GREEN) 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Dimming channel (BLUE) 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Dimming channel (WHITE) 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Dimming channel (COOL) 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Dimming channel (WARM) 
                 Values: 0.00-100.00%, scale: 0.01% 
               
               
                 Occupancy sensitivity level 
                 Values: 0-255 
               
               
                 Ocupancy range of detection 
                 Values: 0-7 
               
               
                 Moving fixture 
                   
               
               
                 Up/down (tilt) 
                   
               
               
                 Direction 
                 Values: 1 = up, 0 = down. 
               
               
                 Type of motion 
                 Values: 1 = absolute, 0 = relative. 
               
               
                 Absolute Position 
                 Values: 0-14,600 Scale = 0.025 degrees) 
               
               
                 Left/right (pan) 
                   
               
               
                 Direction 
                 Values: 1 = left, 0 =right. 
               
               
                 Type of motion 
                 Values: 1 = absolute, 0 = relative. 
               
               
                 Absolute Position 
                 Values: 0-14,600 Scale = 0.025 degrees) 
               
               
                 Beam spread angle 
                   
               
               
                   
                 Values: 0, 255 
               
               
                 Combination of any of the above 
                   
               
               
                 Other suitable fixture parameters 
               
               
                   
               
            
           
         
       
     
     The apparatus may include a receiver. The receiver may be configured to receive a user command. The user command may correspond to a function of the fixture. The apparatus may include a microprocessor. The microprocessor may be configured to generate a fixture control message. The fixture control message may correspond to the function. Generation of a fixture control message may include translation of the fixture control message. 
     The receiver may be configured to receive the user command from a network. Table 4 lists illustrative networks. 
     
       
         
           
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Illustrative networks. 
               
               
                 Illustrative networks 
               
               
                   
               
             
            
               
                 Wide Area Network (e.g., Internet) 
               
               
                 Local Area Network 
               
               
                 DMX 512 
               
               
                 Dali 
               
               
                 Other suitable networks 
               
               
                   
               
            
           
         
       
     
     The receiver may be configured to receive a signal that conforms to a protocol. Table 5 lists illustrative signal protocols. 
     
       
         
           
               
             
               
                 TABLE 5 
               
               
                   
               
               
                 Illustrative signal protocols. 
               
               
                 Illustrative signal protocols 
               
               
                   
               
             
            
               
                 IEEE 802.11 
               
               
                 IEEE 802.15.1 
               
               
                 IEEE 802.3 
               
               
                 ANSI E1.11-2008 (R2018) Entertainment Technology—USITT  
               
               
                 DMX512-AAsynchronous Serial Digital Data 
               
               
                 Transmission Standard for Controlling 
               
               
                 Lighting Equipment and Accessories 
               
               
                 IEC 62386 
               
               
                 TCP/IP 
               
               
                 Other suitable signal protocols 
               
               
                   
               
            
           
         
       
     
     The user command may be a first user command. The user command may conform to a first fixture control protocol. The receiver may be configured to receive a second user command that corresponds to the function. The second user command may conform to a second fixture control protocol. The second fixture control protocol may be different from the first fixture control protocol. 
     The user command may be a first user command. The user command, in a first protocol, may correspond to the fixture function. The fixture function, in a second protocol, may be expressed as a second user command. The second user command may be different from the first user command. The control message may include an instruction. The instruction may correspond to the first user command and the second user command. 
     The microprocessor may be configured to select the instruction in response to the first user command. 
     The microprocessor may be configured to select the instruction in response to the second user command. 
     The microprocessor may be configured to select the instruction based on a table that maps the first user command and the second user command to the instruction. 
     The apparatus may include machine readable memory. The table may be stored in the machine readable memory. 
     The microprocessor may be of several microprocessors that are configured, in aggregate, to allocate power to a fixture control circuit and the fixture. 
     The microprocessor may be of several microprocessors that are configured, in aggregate, to receive the user command from an input channel of input channels, each corresponding to a different fixture control protocol. The microprocessor may be of several microprocessors that are configured, in aggregate, to translate the user command into the control message. 
     The user command may be rendered in a first protocol. The microprocessor may be configured to render the control message in a second protocol that is different from the first protocol. 
     The microprocessor may be a first microprocessor. The apparatus may include a fixture having a second microprocessor. The first microprocessor may be configured to process the user command. The second microprocessor may be configured to process the control message. The second microprocessor may be a microprocessor that is not configured to process the user command. 
     The apparatus may include a fixture support. The fixture support may support the fixture. The microprocessor may be disposed in a power control enclosure. The power control enclosure may be separate from the fixture support. The power control enclosure may be in electrical communication with the fixture support. 
     The microprocessor may be in wired electrical communication with a conductor of the fixture support. 
     The enclosure may be configured to be mounted a wall. 
     The apparatus may include a receptacle for receiving an input communication line. The fixture control message may be configured to change a load of the fixture in response to a voltage change in the input communication line. 
     The change of the load may be proportional to the voltage change. 
     The apparatus may include a frame. The frame may define a cartridge socket. The cartridge socket may be configured to receive a cartridge. The cartridge socket may include input contacts configured to receive the user command. The cartridge may include a physical interface configured to receive a connector having an input format that conforms to the user command. The cartridge may include output contacts that are in electrical communication with respective input contacts. 
     The input format may be mismatched to the input contacts. 
     Table 6 lists illustrative input formats. 
     
       
         
           
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Illustrative input formats. 
               
               
                 Illustrative formats 
               
               
                   
               
             
            
               
                 DMX (Digital Multiplexer) 
               
               
                 DALI (Digital Addressable Lighting Interface) 
               
               
                 Triac or ELV (Phase cut dimmer signal) 
               
               
                 0-10 V dimmer signal 
               
               
                 Z-wave (Z-wave Alliance, Beaverton, Oregon) 
               
               
                 Zigbee (Zigbee Alliance, of San Ramon, California) 
               
               
                 Custom—user defined 
               
               
                 Default—provided in memory 
               
               
                 Other third-party control protocol 
               
               
                 Other suitable input formats 
               
               
                   
               
            
           
         
       
     
     The cartridge may be a first cartridge. The physical interface may be a first physical interface. The connector may be a first connector. The format may be a first format. The output contacts may be first output contacts. The cartridge socket may be configured to receive a second cartridge. The second cartridge may include a second physical interface. The second physical interface may be configured to receive a second connector. The second connector may have a second format that conforms to the user command. The second connector may have output contacts that are, respectively, in electrical communication with the input contacts. 
     The microprocessor may be configured to detect a pre-regulated power level at the receptacle. The fixture control message may be configured to set the load at the fixture in proportion to the pre-regulated power level. 
     The apparatus may include an input power supply that may be configured to receive line voltage. The apparatus may include a control power unit that may include the microprocessor. The apparatus may include a power distribution circuit. The power distribution circuit may be configured to supply a first current to the control power unit. The power distribution circuit may be configured to supply a second current to the fixture. 
     The power supply may reduce the line voltage to a constant operational voltage. The first current may be delivered at the constant operational voltage. The second current may be delivered at the constant operational voltage. 
     The fixture may be configured to be supported by a fixture support. The fixture may be configured to be recessed in the fixture support. The fixture may be configured to be flush-mounted in the fixture support. The fixture may be configured to be pendant from the fixture support. The fixture may be configured to be magnetically suspended from the fixture support. 
     The microprocessor may be a first microprocessor. The fixture may include a second microprocessor. The second microprocessor may be configured to be in electronic communication with the first microprocessor. The second microprocessor may be configured to receive the control message from the first microprocessor. The second microprocessor may be configured to control the fixture responsive to the control message. 
     The apparatus may include a fixture support. The fixture may be a first fixture. The fixture support may support the first fixture. The fixture support may support several second fixtures. The first and second fixture supports may have different lengths. The second fixture supports may have different lengths. The microprocessor may be configured to address the message to the first fixture and not to any of the second fixtures. 
     The fixture may be of a first group of fixtures. The fixture support may support a second group of fixtures. The microprocessor may be configured to address the message only to fixtures in the first group. 
     The apparatus may include a transmitter. The transmitter may be configured to transmit the message to the fixture over wire. The transmitter may be configured to transmit the message to the fixture over a wireless gap. 
     The receiver may be configured to receive the user command from a remote communication unit. The remote communication unit may include a mobile telephone. The remote communication unit may include a wall-mounted control. 
     The receiver may be configured to receive the user command wirelessly. The receiver may be configured to receive the user command over a wire. 
     Table 7 lists illustrative user commands. 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
               
                 Illustrative user commands. 
               
               
                 Illustrative user commands 
               
               
                   
               
             
            
               
                 Voltage level 
               
               
                 Increase intensity 
               
               
                 Decrease intensity 
               
               
                 Increase CCT 
               
               
                 Decrease CCT 
               
               
                 Illustrative user commands 
               
               
                 Power ON 
               
               
                 Power OFF 
               
               
                 Select layout 
               
               
                 Track circadian lighting 
               
               
                 (automatically adjust fixture parameter to match circadian cycles) 
               
               
                 Complement ambient lighting (Light harvesting automation) 
               
               
                 Automatically adjust fixture parameter based on occupancy of a space 
               
               
                 (select occupied, unoccupied scenes) 
               
               
                 Automatically adjust fixture parameter based on occupancy of a space 
               
               
                 (select occupied, unoccupied scenes) 
               
               
                 Motion activation ON 
               
               
                 Motion activation OFF 
               
               
                 Motion deactivation ON 
               
               
                 Motion deactivation OFF 
               
               
                 Select hue for fixture 
               
               
                 Select hue for group 
               
               
                 Select power setting 
               
               
                 Select ambient temperature setting for automatic ON 
               
               
                 Select ambient temperature setting for automatic OFF 
               
               
                 Adjust vertical displacement of an LED 
               
               
                 Adjust horizontal displacement of an LED (e.g., move left/right 5 degs.) 
               
               
                 Adjust tilt angle of an LED 
               
               
                 Adjust pan angle of an LED (e.g., pan to a different heading) 
               
               
                 Adjust light beam spread angle 
               
               
                 Other suitable user commands 
               
               
                   
               
            
           
         
       
     
     A beam spread angle may be an angle between opposed edges of a beam. A beam edge may be defined by a decrease of 50% intensity relative to a maximum intensity of the beam. Beam edges may be identified by a goniophotometer. 
     The microprocessor may be configured to transmit to a remote communication unit lighting layout information. The layout information may identify the fixture support. The layout information may include, for the fixture, a location on the fixture support. The layout information may include, for the fixture, a fixture on the fixture support. 
     The layout information may include, for the fixture, a fixture parameter. 
     The fixture parameter may be a first fixture parameter. The layout information may include, for a second fixture, a second fixture parameter. 
     The fixture may be a first fixture. The location may be a first location. The layout information may include, for a second fixture, a second location on the fixture support corresponding to the second fixture. 
     The fixture support may be a first fixture support. The layout information may identify a second fixture support. The layout information may identify an orientation of the second fixture support relative to the first fixture support. The fixture may be a first fixture. The location may be a first location. The layout information may include, for a second fixture, a second location on the second fixture support corresponding to the second fixture. 
     The remote communication unit may be configured to render a display corresponding to the lighting layout information. 
     The user command may include a command to select, responsive to an ambient light spectrum, a hue of a light beam to be emitted from the fixture. 
     The apparatus may include a photo sensor. The photo sensor may be configured to register a spectrum of ambient light in which the fixture is disposed. 
     The microprocessor may be configured to select, responsive to the spectrum, a coordinated color temperature of a light beam to be emitted from the fixture. 
     The photo sensor may be a first photo sensor. The apparatus may include a second photo sensor. 
     The second photo sensor may be configured to detect a presence of a human in a space in which the fixture support is disposed. The microprocessor may be configured to change a parameter of the fixture based on a presence of the human. The second photo sensor may be configured to detect a departure of a human from a space in which the fixture support is disposed. The microprocessor may be configured to change a parameter of the fixture based on the departure. 
     The first photo sensor and the second photo sensor may be collocated on a substrate. 
     The apparatus may include a sensor integrated circuit. The first photo sensor and the second photo sensor may be part of the sensor integrated circuit. 
     Table 8 lists illustrative control messages. 
     
       
         
           
               
             
               
                 TABLE 8 
               
               
                   
               
               
                 Illustrative control messages. 
               
               
                 Illustrative control messages 
               
               
                   
               
             
            
               
                 Voltage level 
               
               
                 Increase intensity 
               
               
                 Decrease intensity 
               
               
                 Increase CCT 
               
               
                 Decrease CCT 
               
               
                 Power ON 
               
               
                 Power OFF 
               
               
                 Select layout 
               
               
                 Track circadian lighting 
               
               
                 Complement ambient lighting 
               
               
                 Motion activation ON 
               
               
                 Motion activation OFF 
               
               
                 Motion deactivation ON 
               
               
                 Motion deactivation OFF 
               
               
                 Select hue for fixture 
               
               
                 Select hue for group 
               
               
                 Select power setting 
               
               
                 Select ambient temperature setting for automatic ON 
               
               
                 Select ambient temperature setting for automatic OFF 
               
               
                 Adjust vertical displacement of an LED 
               
               
                 Adjust horizontal displacement of an LED 
               
               
                 Adjust tilt angle of an LED 
               
               
                 Adjust pan angle of an LED 
               
               
                 Adjust light beam spread angle 
               
               
                 Other suitable control messages 
               
               
                   
               
            
           
         
       
     
     The apparatus may include a brace. The brace that may be configured to align a fixture support with an electrical accessory to the fixture support. The apparatus may include a circuit. The circuit may be configured to transmit power between the fixture support and the accessory. The fixture support may define a fixture docking area. The fixture docking area may be configured to receive a fixture. The fixture docking area may be configured to removably retain the fixture. The brace may be detachably engageable with the fixture support. Engagement of the brace with the fixture support may be an engagement that does not reduce the area. 
     The circuit may include an electrical terminal. The terminal may be elastically biases. The terminal may include a contact. The contact may electrically contact the fixture support when the brace engages the fixture support. 
     The circuit may be a first circuit. The contact may be a first contact. The apparatus may include a second circuit. The second circuit may include a second contact. The second contact may electrically contact the fixture support when the brace engages the fixture support. 
     The first and second circuits may be electrically isolated from each other inside the brace. The first circuit may be configured to conduct power. The second circuit may be configured to conduct a communication signal. 
     The apparatus may include an accessory. The accessory may include a power terminal in electrical communication with the first contact. The accessory may include a signal terminal in electrical communication with the second contact. The accessory may include a wall that abuts the area. 
     The accessory may include a first closed-loop conductor slidingly engaged with a first power terminal that may be in electrical communication with the first contact. The accessory may include a second closed-loop conductor slidingly engaged with a second power terminal that may be in electrical communication with the second contact. The accessory may include a guide. The guide may be configured to maintain electrical communication of the first power terminal with the first closed-loop conductor. The guide may be configured to maintain electrical communication of the second power terminal with the second closed-loop conductor. The guide may be configured to maintain the electrical communication while the brace is repositioned along the first and second closed-loop conductors. 
     The brace may be repositionable continuously along the first and second closed-loop conductors. 
     The apparatus may include a power switch. The power switch may be configured to break electrical communication between the first closed-loop conductor and the first circuit. 
     The brace may be of a plurality of braces. The first and second closed-loop conductors may be configured to be electrically engaged by the plurality of braces concurrently with each other. 
     The brace may be a first brace. The fixture support may be a first fixture support. The area may be a first area. The accessory may include a second brace. The second brace may extend at a fixed angle relative to the first brace. The second brace may be configured to detachably engage a second fixture support at the angle relative to the first fixture support. The second fixture support may include a second a fixture docking area. The second fixture docking area may be configured to receive the fixture. The second fixture docking area may be configured to receive removably the fixture. Engagement of the second brace with the second fixture support may be an engagement that does not reduce the second area. 
     The circuit may be a first circuit. The second brace may include a second circuit that may be configured to transmit power between the first circuit and the second fixture support. 
     Table 9 lists illustrative ranges that may include the angle. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 Illustrative angle ranges. 
               
               
                 Illustrative angle ranges 
               
               
                 (degrees of arc) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 29 
               
               
                   
                 30 
                 44 
               
               
                   
                 45 
                 59 
               
               
                   
                 60 
                 74 
               
               
                   
                 75 
                 89 
               
               
                   
                 90 
                 104 
               
               
                   
                 105 
                 119 
               
               
                   
                 120 
                 134 
               
               
                   
                 135 
                 149 
               
               
                   
                 150 
                 164 
               
               
                   
                 165 
                 179 
               
               
                   
                 180 
                 194 
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper limits 
               
               
                   
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     The apparatus may include a connector that may be configured to join a first end of a first fixture support defining a first fixture-docking area to a second end of a second fixture support defining a second fixture-docking area. Connection by the connector may form a joint that does not subtract docking area from a third area that is defined as a sum of the first fixture-docking area and the second fixture-docking area. 
     The first fixture-docking area may be configured to receive the device. 
     The second fixture-docking area may be configured to receive the device. 
     The first docking area may include a first mounting surface. The second docking area may include a second mounting surface. The connector may be configured to join the first and second surfaces such that the first and second surfaces are flush with each other. The connector may be configured to join electrically a first power rail of the first fixture support to a second power rail of the second fixture support. The power rail may be configured to transmit power. The power rail may be configured to transmit control messages, as in a power line communication (“PLC”) architecture. 
     The connector may be configured to join electrically a first control communication bus of the first fixture support to a second control communication bus of the second fixture support. 
     The connector may be configured to hold a second end of a second mounting surface in abutment with a first end of a first mounting surface. 
     The connector may be configured to hold the second end spaced apart from the first end with no structure intervening between the second end and the first end. 
     The first fixture support may provide a first continuous stretch of locations at which a light fixture may be mountable on the first surface. The second fixture support may provide a second continuous stretch of locations at which the light fixture may be mountable on the second surface. The connector may be configured to form, from the first and second continuous stretches, a third continuous stretch of locations at which the light fixture may be mountable. The third continuous stretch may include the first and second stretches. 
     The apparatus may include a power rail jumper. The power rail jumper may be configured to join electrically a first power rail of the first fixture support to a second power rail of the second fixture support. A first mounting surface of the first fixture support may be configured to support a fixture. A second mounting surface of the second fixture support may be configured to support the fixture. The power rail jumper may be configured to connect with the first power rail at a first location behind the first surface. The power rail jumper may be configured to connect with the second power rail at second location behind the second surface. The fixture may include a light fixture. 
     The connector may include a first projection. The connector may include a second projection. The first projection may be configured to mate with the first fixture support. The second projection may be configured to mate with the second fixture support. 
     The first projection may extend along a plane. The second projection may extend along the plane. 
     The plane may be horizontal when the apparatus may be in operation. 
     The first projection may include a male engagement component. The male engagement component may be configured to mate with a female engagement component on the first fixture support. 
     The first projection may include a female engagement component configured. The female engagement component may be configured to mate with a male engagement component on the first fixture support. 
     The apparatus may include a power rail jumper that is configured to provide power conductivity between a first power rail of the first fixture support and a second power rail of the second fixture support. 
     The apparatus may include a communication bus jumper that is configured to provide signal conductivity between a first communication bus of the first fixture support and a second communication bus of the second fixture support. 
     The first fixture support may include a first mounting surface. The second fixture support may include a second mounting surface. The connector, in operation, may hold a second end of the second mounting surface level with a first end of the first mounting surface. 
     The first projection and the second projection, in operation, may hold the second mounting surface in abutment with the first mounting surface. 
     The first projection and the second projection, in operation, may hold the second mounting surface spaced apart from the first mounting surface with no structure intervening between the second mounting surface and the first mounting surface. 
     The first projection may include a first plate that may be configured for insertion, in the first fixture support, between: (a) a first U-channel spine; and (b) a first control communication bus and a first power rail. The second projection may include a second plate that may be configured for insertion, in the second fixture support, between: (a) a second U-channel spine; and (b) a second control communication bus and a second power rail. 
     The apparatus may be configured so that neither the first plate nor the second plate intervenes between butt-ends of the first and second fixture supports. The apparatus may be configured so that neither the first plate nor the second plate intervenes interferes with placement of a light fixture in the U-channel. 
     The apparatus include a junction. The junction may define a central axis that may define continuous circumferential angles about the axis. The junction may be configured to support a fixture support bracket at any of the angles. The junction may be configured to provide electrical communication with the bracket at any of the angles. The junction may include a track configured to support the bracket. The junction may include a conductor that is configured to provide the electrical communication. 
     The track may be configured to slidingly support the bracket. The conductor may be configured to provide the electrical communication at any of the angles to which the bracket is, in operation, moved. 
     The bracket may be configured to support an end of an elongated fixture support. 
     The bracket may be configured to provide the electrical communication from the conductor to the fixture support. 
     The bracket may include a projection that extends radially away from the central axis. The bracket may be a first bracket. The electrical communication may be a first electrical communication. The fixture support may be a first fixture support. A second bracket that may be configured to slidingly engage the track. The second bracket that may be configured to slidingly engage the track. The second bracket may be configured to provide a second electrical communication from the conductor to a second fixture support. 
     The second bracket may include a projection that extends radially away from the central axis. 
     The apparatus may include a third bracket. The third bracket may be configured to slidingly engage the track. The third bracket may be configured to provide a third electrical communication from the conductor to a third fixture support. 
     The third bracket may include a projection that extends radially away from the central axis. 
     The first fixture support may include a first mounting surface. The second fixture support may include a second mounting surface. The junction, in operation, may hold a second end of the second mounting surface level with a first end of the first mounting surface. 
     The conductor may be a first conductor. The electrical communication may be a first electrical communication. A second conductor that may be configured to provide a second electrical communication with the bracket. The first conductor and the second conductor may be configured to provide the respective first and second electrical communications at any of the angles to which the bracket is, in operation, moved. 
     The first conductor and the second conductor in operation may provide power to the bracket. 
     The first conductor and the second conductor in operation may provide a communication signal to the bracket. 
     The apparatus may include a third conductor that may be configured to provide a third electrical communication with the bracket. 
     The apparatus may include a fourth conductor that may be configured to provide a fourth electrical communication with the bracket. The third conductor and the fourth conductor may be configured to provide the respective third and fourth electrical communications at any of the angles to which the bracket is, in operation, moved. 
     The third conductor and the fourth conductor in operation may provide power to the bracket. 
     The third conductor and the fourth conductor in operation may provide a communication signal to the bracket. 
     The conductor may be a first conductor. The apparatus may include a second conductor. The apparatus may include a third conductor. The apparatus may include a fourth conductor. Each of the first, second, third and fourth conductors may define a continuous loop about the central axis. 
     The junction may include a frame. The frame may support the conductors. The frame may support the track. The frame may include a plate on which the conductors may be disposed. 
     The plate may be a first plate. The apparatus may include a second plate. The first and second plates may be spaced apart by a spacer. The first plate, the second plate and the spacer may define a receptacle. The receptacle may be configured to receive the bracket. The receptacle may be configured to slidably support the bracket such that the bracket may be movable about the spacer. 
     The apparatus may include a fixture head. The fixture head may include a back wall. The back wall may have a back side that may be configured to be retained against a fixture support. The back wall may have a front side, opposite the back side, that, in relation to the back side, defines a forward direction. The apparatus may include a detent. The detent may extend from the head. The detent may be configured to engage the fixture support to retain a position of the head relative to the fixture support. The apparatus may include a release. The release may be disposed inside the fixture head. The release may be configured to withdraw the detent from the fixture support. The release may be accessible only from a location forward of the release. 
     The fixture head may support engagement of a fixture with a fixture support. The fixture support may support engagement of any suitable object, including signage, with the fixture support. 
     The release may be disposed forward of the back side. 
     The release may be disposed such that, in operation, the back wall may be between the fixture support and the release. 
     The back side may define, in relation to the front side, a rear direction. The back side may be configured to be retained against the fixture support such that the fixture support is rear of the back side. The release may be disposed forward of the back side. 
     The detent may be configured to bridge between the head and the fixture support to engage the fixture support. 
     The head may have a first side opposite a second side. The detent bridges between the first side and the fixture support. 
     The detent may be biased to engage the fixture support. 
     The release may define an engagement element. The engagement element may be configured to be engaged to operate the release. The release may include a slide, a button, a lever or any other suitable release element. 
     The engagement element may be disposed parallel the back wall. 
     The apparatus may include a side wall. The side wall may extend perpendicular the back wall. The engagement element may be disposed parallel the side wall. 
     The engagement element may include an edge. The edge may be configured to be engaged by a tip of an elongated hand-held instrument. 
     The engagement element may define a catch. The catch may be configured to be engaged by a tip of an elongated hand-held instrument. 
     The engagement element may be configured to be operated by a user finger. 
     The head in operation may span a recess of the fixture support in a direction transverse the fixture support such that a side wall of the head may be flush with the fixture support. 
     The side wall may be supported by the back wall. The side wall may define, with the back wall, an interior. The release may be disposed in the interior. 
     The side wall may define an open side of the head. The release may be accessible only via the open side. The release may be a release that is not accessible via the side wall. 
     The head may be configured to be seated in a recess defined by the fixture support. The detent may be configured to secure the head in the recess. The detent may be configured to bridge between the head and the fixture support to engage the fixture support. 
     The head may have a first side opposite a second side. The detent may bridge between the first side and the fixture support. 
     The head in operation may span the recess in a direction transverse the fixture support such that the first and second sides are flush with the fixture support. 
     The detent may be biased to engage the fixture support. 
     The release may define an edge that may be configured to be engaged by a tip of an elongated hand-held instrument. 
     The head may define an interior. The release may be disposed in the interior. 
     The head may include a side that in operation lies flush against a spine of the recess. The side, relative to the spine, may define a downward direction. A fixture power conductor may be disposed in the interior. The release, in operation, may be disposed below the side. The release, in operation, may be disposed above the fixture power conductor. 
     An LED circuit may be disposed in the interior. The release, in operation, may be disposed below the side. The release, in operation, may be disposed below the side above the LED circuit. The release, in operation, may be disposed above the LED emitter. 
     A reflector may be disposed in the interior. The release, in operation, may be disposed above the reflector. 
     A translucent layer may be disposed against the head. The release, in operation, may be disposed above the translucent layer. 
     The apparatus may include a light fixture. The light fixture may include an LED emitter. The light fixture may be configured to depend from a fixture support. The light fixture may be configured to emit a beam. The light fixture may be configured to receive a control message from a conductor of the fixture support. The light fixture may be configured to, in response to the control message, adjust a beam-spread angle of the beam. 
     The conductor may include a bus. The conductor may include a power bus. The conductor may include a communication bus. 
     The apparatus may include a lens. The lens may be configured to adjust the beam-spread angle in response to an electrical field applied to the lens. The lens may include a liquid crystal. 
     The light fixture may be further configured to adjust, in response to the control message, a height along a vertical direction that passes through the fixture when the fixture is in operation. 
     The light fixture may be configured to adjust, in response to the control message, a tilt angle between a centerline of the beam and a vertical direction that passes through the fixture when the fixture is in operation. 
     The light fixture may be configured to adjust, in response to the control message, a pan angle defined about a vertical direction that passes through the fixture when the fixture is in operation. 
     The light fixture may include a receiver. The light fixture may include a tilt actuator. The light fixture may include a pan actuator. The receiver may be configured to be in electronic communication with the tilt actuator. The receiver may be configured to be in electronic communication with the pan actuator. The tilt actuator may be configured to change an angle between a centerline of the beam and a vertical direction that passes through the fixture when the fixture may be in operation. The pan actuator may be configured to angularly translate the emitter about the vertical direction. 
     The light fixture may include a magnetic coupler. The magnetic coupler may be configured to suspend the fixture from the fixture support. The magnetic coupler may include a permanent magnet. The magnetic coupler may include ferrous metal. The magnetic coupler may be intrinsic to a wall of the fixture. 
     The light fixture may include a power contact. The power contact may be configured to contact a power rail on the fixture support. The light fixture may include further a power contact. The power contact may be configured to contact a power rail on a fixture support. The power contact may be configured to be held in contact with the power rail by the magnetic coupler. The power contact may be configured to push against the power rail. The power contact may be configured to be held against the power rail solely by the magnetic coupler. 
     The light fixture may include a communication bus contact. The communication bus contact may be configured to contact a communication bus on the fixture support. The communication bus contact may be configured to push against a power rail of the fixture support. The communication bus contact may be configured to be held against the power rail solely by the magnetic coupler. 
     The tilt actuator may be configured to move a housing, relative to the vertical direction, through an angular displacement of 180°. Table 10 lists illustrative ranges that may include the tilt angle. 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                 Illustrative tilt angle ranges. 
               
               
                 Illustrative tilt angle ranges 
               
               
                 (degrees of arc) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 29 
               
               
                   
                 30 
                 44 
               
               
                   
                 45 
                 59 
               
               
                   
                 60 
                 74 
               
               
                   
                 75 
                 89 
               
               
                   
                 90 
                 104 
               
               
                   
                 105 
                 119 
               
               
                   
                 120 
                 134 
               
               
                   
                 135 
                 149 
               
               
                   
                 150 
                 164 
               
               
                   
                 165 
                 179 
               
               
                   
                 180 
                 194 
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper limits 
               
               
                   
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     The pan actuator may be configured to angularly translate the emitter through an angular displacement of 360° or more. Table 11 lists illustrative ranges that may include the pan angle. 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 Illustrative pan angle ranges. 
               
               
                 Illustrative pan angle ranges 
               
               
                 (degrees of arc) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 29 
               
               
                   
                 30 
                 44 
               
               
                   
                 45 
                 59 
               
               
                   
                 60 
                 74 
               
               
                   
                 75 
                 89 
               
               
                   
                 90 
                 104 
               
               
                   
                 105 
                 119 
               
               
                   
                 120 
                 134 
               
               
                   
                 135 
                 149 
               
               
                   
                 150 
                 164 
               
               
                   
                 165 
                 179 
               
               
                   
                 180 
                 194 
               
               
                   
                 165 
                 179 
               
               
                   
                 180 
                 194 
               
               
                   
                 195 
                 209 
               
               
                   
                 210 
                 224 
               
               
                   
                 225 
                 239 
               
               
                   
                 240 
                 254 
               
               
                   
                 255 
                 269 
               
               
                   
                 270 
                 284 
               
               
                   
                 285 
                 299 
               
               
                   
                 300 
                 314 
               
               
                   
                 315 
                 329 
               
               
                   
                 330 
                 344 
               
               
                   
                 345 
                 359 
               
               
                   
                 360 
                 365 
               
               
                   
                 366 
                 366+ 
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper 
               
               
                   
                 limits 
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     The apparatus may include an LED emitter. The apparatus may be configured to The apparatus may be configured to depend from a fixture support. The apparatus may be configured to receive a control message from a conductor of the fixture support. The apparatus may be configured to, in response to the control message, pan the LED emitter. The apparatus may be configured to, in response to the control message, tilt the LED emitter. The apparatus may be configured to adjust, in response to the control message, a beam-spread angle of a beam to be emitted, in operation, from the emitter. 
     The apparatus may include a base. The apparatus may include a housing. The apparatus may include an LED emitter. The LED emitter may be disposed in the housing. The apparatus may include a collar. The collar may, in operation, by rotatable relative to the housing to adjust a beam spread angle of a beam emitted from the emitter. 
     The base may include a fixture head. The fixture head may include a latch. The fixture head may include a pick-up unit. 
     The base may be configured to be docked in an interior of a U-channel fixture support. Docking may include causing a mechanical engagement of the base with the fixture support. Docking may include making electrical contact to transfer power between the base and the fixture support. The base may be configured to support the housing at different user-selectable heights relative to the U-channel fixture support. 
     The collar may be threadingly engaged with the housing. 
     Linear translation of the collar relative to a central axis of the housing changes a distance between the emitter and a lens. 
     The housing may include a detent to prevent the collar from separating from the housing. 
     The housing may include an annular recess adjacent threads through which the collar rotates. The detent may include a “C”-clip. The “C”-clip may be disposed in the recess. The “C”-clip may defines a circumference. The “C”-clip may a reentrant angle interior the circumference. 
     The apparatus may include an articulating joint. The articulating joint may provide freedom for the housing to be manually moved vertically relative to the base. 
     The housing and the support may be configured such that an entirety of the housing may be movable into the interior. 
     The housing may include a lip distal the base. The fixture support may include a U-channel spine. The fixture support may include an edge distal the spine. The lip may be movable into the interior, past the edge. 
     The articulating joint may be a first articulating joint. The apparatus may include a second articulating joint. The second articulating joint may provide freedom for the housing to rotate about a vertical direction that passes through the base when the base is in operation. 
     The apparatus may include a third articulating joint. The third articulating joint may provide freedom for the housing to tilt relative to the base. 
     The apparatus may include an LED emitter disposed in a housing. The apparatus may include a base. The base may be configured to dock to a fixture support. The apparatus may include a cord. The cord may have a first end. The first end may be electrically terminated in the base. The cord may have a second end. The second end may be electrically terminated in the housing. The cord may be configured to suspend the housing from the base. The housing may be configured to engage the cord at a location along the cord between the first end and the second end to suspend the housing at the location. The housing may be configured to store a slack length of the cord in the housing. 
     The cord may include a plurality of locations continuously distributed along the cord. The housing may be configured to engage the cord at any location in the plurality. Engagement of the cord by the housing at the location may retain the housing at a height corresponding to the location. The housing may be configured to engage the cord by mechanical interference with the cord. 
     The height may be adjustable by manually withdrawing the cord from the housing. The height may be adjustable by manually pushing the cord into the housing. 
     The housing may include a normally-closed gripper. The gripper may be configured to grip the cord at the location. The gripper may be configured to relax in response to passage of the cord into the housing. The passage may be a manual passage. The gripper may be configured for manual insertion of the cord into the housing. The gripper may be configured for manual withdrawal of the cord from the housing. 
     The gripper may include a spring. The spring may be disposed coaxially about an axis of the cord. The gripper may include a bumper. The bumper may be supported by the spring. Compression of the spring may displace the bumper radially away from the axis to release the cord. Urging of the cord into the housing may cause the compression. 
     Under a first tension from the housing, the bumper may engage the cord to suspend the housing. Under a second tension from a user, the cord may be slidable out of the housing against the bumpers. The second tension may be greater than the first tension. 
     The apparatus may include an LED emitter. The emitter may be disposed in a housing. The apparatus may include a ring. The ring may include a baffle. The ring may be configured to be supported by the housing at a first user-selectable position relative to the housing. The ring may be configured to be supported by the housing at a second user-selectable position relative to the housing. The ring may be configured to be supported by the housing at a third user-selectable position relative to the housing. The third user-selectable position may be continuously selectable between the first user-selectable position and the second user-selectable position. 
     The ring may configured to be moved between the positions without rotation about a central axis of the ring. At the positions, in operation, rotation of the ring may change a beam spread angle of light emitted from the LED. Rotating the ring may cause a linear displacement of a lens relative to the LED emitter. Projecting the ring away from the housing, in operation, may prevent light from the emitter from illuminating outside a region defined by a cut-off angle. The cut-off angle may be in the range 0-45° below a horizontal plane defined by the lower edge of the ring. Projecting the ring away from the housing, in operation, may eliminate glare experienced by a person at a distance from the vertical axis of the housing. The higher the ring is set, the greater is the distance at which the person may experience glare. 
     The ring may be configured to be manually rotated by a user. The ring may be configured to nest in the housing. The ring may be configured to be manually telescopically extended away from the housing. The ring may be configured to be manually telescopically moved relative to the housing, without, in operation, changing the beam spread angle. 
     The apparatus may include a slotted bushing. The ring may be configured to translate along the axis relative to the bushing, and not rotate relative about the axis relative to the bushing. The bushing may be affixed to the housing. The bushing may be rotatable with respect to the housing. 
     Rotation of the bushing may change a distance between the emitter and lens. 
     The apparatus may include a light fixture depending from a fixture support and configured to emit a beam of light. The apparatus may include a detector that is configured to generate a signal based on detection of a target. The apparatus may include a microprocessor. The microprocess or may be configured to direct the beam to a target based on a first location of the target. The microprocessor may be configured to redirect the beam to the target when the target moves to a second location. Table 12 lists illustrative target types. 
     
       
         
           
               
             
               
                 TABLE 12 
               
               
                   
               
               
                 Illustrative target types. 
               
               
                 Illustrative target types 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                   
                   Active 
               
               
                   
                   
                   RF broadcast circuit 
               
               
                   
                   
                   Bluetooth 
               
               
                   
                   
                   Optical emitter 
               
               
                   
                   
                   Acoustic signal generator 
               
               
                   
                   
                   Reactive 
               
               
                   
                   
                  RFID 
               
               
                   
                   
                   Acoustic/Magnetic signal generator 
               
               
                   
                   
                   Acoustic 
               
               
                   
                   
                  Passive 
               
               
                   
                   
                   Optical (//) 
               
               
                   
                   
                   visual 
               
               
                   
                   
                   IR 
               
               
                   
                   
                   UV 
               
               
                   
                   
                   AR-based natural feature 
               
               
                   
                   
                   Other suitable target types 
               
               
                   
                   
               
            
           
         
       
     
     The target may be configured to change from a low power mode to a high power mode upon detection of an acceleration. In the low power mode, the target may consume energy at a rate that is too low to emit a locating signal. In the high power mode, the target may consume energy at a rate that is not too low to emit a locating signal. 
     The microprocessor may be configured to adjust a beam parameter of the beam so that when the target moves from the first location to the second location, a metric of the beam at the target does not change. A beam parameter is an adjustable parameter of a beam, as emitted from the fixture. A metric is a state of the beam as observed at the target. Table 13 lists illustrative beam parameters. 
     
       
         
           
               
             
               
                 TABLE 13 
               
               
                   
               
               
                 Illustrative beam parameters. 
               
               
                 Illustrative beam parameters 
               
               
                   
               
             
            
               
                 Beam-angle spread 
               
               
                 Luminous flux 
               
               
                 Spectral power profile 
               
               
                 Coordinated color temperature 
               
               
                 Fixture parameter 
               
               
                 Other suitable beam parameters 
               
               
                   
               
            
           
         
       
     
     Table 14 lists illustrative beam metrics. 
     
       
         
           
               
             
               
                 TABLE 14 
               
               
                   
               
               
                 Illustrative beam metrics. 
               
               
                 Illustrative beam metrics 
               
               
                   
               
             
            
               
                 Two-dimensional luminous flux 
               
               
                 Beam width transverse to the beam 
               
               
                 Beam width along a horizontal plane 
               
               
                 Beam area in a horizontal plane 
               
               
                 Beam Diameter 
               
               
                 Elliptical axis ratio 
               
               
                 Other suitable beam metrics 
               
               
                   
               
            
           
         
       
     
     The apparatus may include machine readable memory. The microprocessor may be configured to store in the memory a reference bearing from the light fixture to the target. The bearing may include a pan angle. The bearing may include a tilt angle. The microprocessor may transform a pan angle by 180° to account for a negative tilt angle. The reference bearing may correspond to the first location. The microprocessor may be configured to adjust a beam parameter of the beam at the second location to conform to a predetermined instruction corresponding to the second location. Table 15 lists illustrative predetermined instructions. A metric may be a value that quantifies a beam parameter. 
     
       
         
           
               
             
               
                 TABLE 15 
               
             
            
               
                   
               
               
                 Illustrative predetermined instructions. 
               
               
                 Illustrative predetermined instructions 
               
            
           
           
               
               
            
               
                 Illustrative instructions 
                 Illustrative functionality 
               
               
                   
               
               
                 Conform a second-location metric of the beam 
                 Provides at the second location the same metric  
               
               
                 to a first-location metric of the beam. 
                 that was provided at the first location 
               
               
                 Conform a second-location metric of the beam 
                 Provides at the second location a metric  
               
               
                 to a predetermined metric corresponding to the 
                 previously set for the second location 
               
               
                 second location. 
                   
               
               
                 Conform a second-location beam parameter to 
                 Provides for the second location a beam parameter 
               
               
                 a predetermined beam parameter corresponding 
                 previously set for the second location 
               
               
                 to the second location 
                   
               
               
                 Conform a second-location beam parameter in 
                 Provides for the second location a beam parameter  
               
               
                 response to an ambient wavelength-intensity 
                 that is responsive, in a predetermined manner, to  
               
               
                 spectrum at the second location. 
                 an ambient light spectrum sensed at the second  
               
               
                   
                 location in connection with providing illumination  
               
               
                   
                 at the second location. 
               
               
                 Conform a second-location metric of the beam 
                 Provides at the second location a metric that is  
               
               
                 in response to an ambient wavelength-intensity 
                 responsive, in a predetermined manner, to an  
               
               
                 spectrum at the second location. 
                 ambient light spectrum sensed at the second  
               
               
                   
                 location in connection with providing illumination  
               
               
                   
                 at the second location. 
               
               
                 Other suitable instructions 
                 Other suitable functionality 
               
               
                   
               
            
           
         
       
     
     The microprocessor may be configured to store in the memory a reference beam parameter that corresponds to the first location. The microprocessor may be configured to store in the memory a reference beam metric that corresponds to the first location. 
     The microprocessor may be configured to calculate, for the second location, a redirected bearing from the light fixture to the target. 
     The microprocessor may be configured to calculate, for the second location, a redirected beam parameter that causes the beam metric, when the target is at the second location, to be the same as the reference metric. 
     The microprocessor may be further configured to receive from a user an instruction to set a reference beam profile. The reference beam profile may include one or more beam parameters. The reference beam profile may include one or more beam metrics. The apparatus may capture a reference beam profile from a live beam from the fixture. 
     The microprocessor may be configured to receive from a user an instruction to reset a reference beam profile. The beam may have a beam spread angle. The light fixture may include a lens. The lens may be configured to reshape the beam in response to an electric field applied to the lens. The lens may be available, for example, under the tradename LENSVECTOR (from LensVector Inc., San Jose, Calif.). The lens may be configured to adjust the beam spread angle between a first value and a second value, continuously. The first value may be a value that is not less than 15. The second value may be a value that is not more than 40. 
     Table 16 lists illustrative detector types. 
     
       
         
           
               
             
               
                 TABLE 16 
               
               
                   
               
               
                 Illustrative detector types. 
               
               
                 Illustrative detector types 
               
               
                   
               
             
            
               
                 Camera 
               
               
                 Microphone 
               
               
                 RF antenna 
               
               
                 Optical sensor 
               
               
                 Acoustic sensor 
               
               
                 Other suitable target types 
               
               
                   
               
            
           
         
       
     
     The microprocessor may be disposed on the fixture support. The microprocessor may be disposed in a lighting power control enclosure. The enclosure may in operation be spaced apart from the fixture support. The enclosure may in operation be in electrical communication with the fixture support. 
     The beam may be a first beam. The apparatus may include a second light fixture that is configured to emit a second beam of light. The microprocessor may be configured to direct the second beam to the target based on the first location. 
     The light fixture may be a first light fixture. The fixture support may be a first fixture support. The apparatus may include a second light fixture that is configured to be supported by a second fixture support. The second fixture support may be a fixture support that is not fixed directly to the first fixture support. 
     The second light fixture may be configured to be supported by a second fixture support. The apparatus may include a brace that fixes the second fixture support to the first fixture support. 
     The detector may be a first detector. The beam may be a first beam. The target may be first target. The signal may be a first signal. The apparatus may include a second light fixture depending from the fixture support and configured to emit a second beam of light. The second detector may be configured to generate the second signal based on detection of the second target. The microprocessor may be configured to direct the first beam to the first target based on the first signal. The microprocessor may be configured to direct the second beam to a second target based on the second signal. 
     The apparatus may include a current-regulated LED circuit. The current-regulated LED circuit may be configured to receive control information corresponding to the LED emitter. The current-regulated LED circuit may be configured to provide power to the LED emitter based on control information addressed to the circuit. The current-regulated LED circuit may be configured to provide power to the LED emitter. The apparatus may include a non-polar socket that may be in electrical communication with the LED circuit. The LED circuit may include a PM2071 current regulation device. 
     The LED emitter may be a first LED emitter. The LED circuit may be a first LED circuit. The information may be first information. The apparatus may include a second LED emitter. The apparatus may include a second LED circuit. The second LED circuit that may be configured to receive second control information corresponding to the second LED emitter. The second LED circuit that may be configured to provide power to the second LED emitter. The second information may be addressed to the second LED circuit. The second information may be information that is not addressed to the first LED circuit. The first LED circuit may be mounted on a first lamina section having a first power rail configured to receive power from a power source. The second LED circuit may be mounted on a second lamina section having a second power rail, electrically parallel the first power rail, that may be configured to receive power from the power source. The information may include a fixture parameter. The information may include a beam parameter. 
     The apparatus may include a DC power supply. The apparatus may include a transmission line having a length. The current-regulated LED circuit may include a current regulator. The length may extend from the DC power supply to the socket. The transmission line may include power conductors. The power conductors may have a wire diameter. The LED circuit may have a linear light-output density, which may be quantified in terms of lumens/(foot of lamina or laminae). 
     Table 17 lists illustrative minimum values of the length. 
     
       
         
           
               
             
               
                 TABLE 17 
               
             
            
               
                   
               
               
                 Illustrative ranges for minimum values of the length. 
               
               
                 Illustrative ranges for minimum values of the length (ft) 
               
               
                 Range 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 &lt;20  
                 20 
               
               
                   
                 20 
                 40 
               
               
                   
                 40 
                 60 
               
               
                   
                 60 
                 80 
               
               
                   
                 80 
                 100 
               
               
                   
                 100 
                 120 
               
               
                   
                 120 
                 140 
               
               
                   
                 140 
                 160 
               
               
                   
                 160 
                 180 
               
               
                   
                 180 
                 200 
               
               
                   
                 200 
                 220 
               
               
                   
                 220 
                 240 
               
               
                   
                 240 
                 260 
               
               
                   
                 260 
                 280 
               
               
                   
                 280 
                 300 
               
               
                   
                 300 
                 320 
               
               
                   
                 320 
                 340 
               
               
                   
                 340 
                 360 
               
               
                   
                 360 
                 380 
               
               
                   
                 380 
                 400 
               
               
                   
                 400 
                 420 
               
               
                   
                 420 
                 440 
               
               
                   
                 440 
                 460 
               
               
                   
                 460 
                 480 
               
               
                   
                 480 
                 500 
               
               
                   
                 500 
                 520 
               
               
                   
                 520 
                 540 
               
               
                   
                 540 
                 560 
               
               
                   
                 560 
                 580 
               
               
                   
                 580 
                 600 
               
               
                   
                 600 
                 &gt;600 
               
               
                   
                 Other suitable 
                 Other suitable 
               
               
                   
                 ranges of 
                 ranges of 
               
               
                   
                 lengths 
                 lengths 
               
               
                   
                   
               
            
           
         
       
     
     The apparatus may include a lamina section. The lamina section may include a circuit board. The LED emitter may be mounted on the lamina section. The LED circuit may be mounted lamina section. The socket may be mounted lamina section. 
     The LED emitter may be a first LED emitter. The LED circuit may be a first LED circuit. The apparatus may include a second LED emitter. The apparatus may include a second current-regulated LED circuit. The first LED circuit and the first LED emitter together may define a first string. The second current-regulated LED circuit and the second LED emitter together may define a second string. The first string may conduct from a hot conductor to a first neutral conductor. The second string may conduct from the hot conductor to a second neutral conductor. The hot conductor, the first neutral conductor and the second neutral conductor may be in electrical communication with the socket. 
     The information may be first information. The second current-regulated LED circuit that may be configured to receive second information corresponding to the second LED emitter. The second current-regulated LED circuit that may be configured to provide power to the second LED emitter. The first information may correspond to a first power. The second information may correspond to a second power. A ratio of output from the second LED emitter to output from the first LED emitter may be a function of a ratio of the second power to the first power. 
     The first LED may be configured to emit light having a first coordinated color temperature (“CCT”). The second LED may be configured to emit light having a second CCT. The second CCT may be greater than the first CCT. Table 18 lists illustrative ranges that may include nominal CCT values for the first and second CCTs. 
     
       
         
           
               
             
               
                 TABLE 18 
               
             
            
               
                   
               
               
                 Illustrative ranges that may include nominal CCT values for the first 
               
               
                 and second CCTs. 
               
               
                 Illustrative ranges (° K.) 
               
               
                 Range 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 1,800 
                 1,849 
               
               
                   
                 1,850 
                 1,899 
               
               
                   
                 1,900 
                 1,949 
               
               
                   
                 1,950 
                 1,999 
               
               
                   
                 2,000 
                 2,049 
               
               
                   
                 2,050 
                 2,099 
               
               
                   
                 2,100 
                 2,149 
               
               
                   
                 2,150 
                 2,199 
               
               
                   
                 2,200 
                 2,249 
               
               
                   
                 2,250 
                 2,299 
               
               
                   
                 2,300 
                 2,349 
               
               
                   
                 2,350 
                 2,399 
               
               
                   
                 2,400 
                 2,449 
               
               
                   
                 2,450 
                 2,499 
               
               
                   
                 2,500 
                 2,549 
               
               
                   
                 2,550 
                 2,599 
               
               
                   
                 2,600 
                 2,649 
               
               
                   
                 2,650 
                 2,699 
               
               
                   
                 2,700 
                 2,749 
               
               
                   
                 2,750 
                 2,799 
               
               
                   
                 &lt;2,800 
                 2,799 
               
               
                   
                 2,800 
                 2,849 
               
               
                   
                 2,850 
                 2,899 
               
               
                   
                 2,900 
                 2,949 
               
               
                   
                 2,950 
                 2,999 
               
               
                   
                 3,000 
                 3,049 
               
               
                   
                 3,050 
                 3,099 
               
               
                   
                 3,100 
                 3,149 
               
               
                   
                 3,150 
                 3,199 
               
               
                   
                 3,200 
                 3,249 
               
               
                   
                 3,250 
                 3,299 
               
               
                   
                 3,300 
                 3,349 
               
               
                   
                 3,350 
                 3,399 
               
               
                   
                 3,400 
                 3,449 
               
               
                   
                 3,450 
                 3,499 
               
               
                   
                 3,500 
                 3,549 
               
               
                   
                 3,550 
                 3,599 
               
               
                   
                 3,600 
                 3,649 
               
               
                   
                 3,650 
                 3,699 
               
               
                   
                 3,700 
                 3,749 
               
               
                   
                 3,750 
                 3,799 
               
               
                   
                 3,800 
                 3,849 
               
               
                   
                 3,850 
                 3,899 
               
               
                   
                 3,900 
                 3,949 
               
               
                   
                 3,950 
                 3,999 
               
               
                   
                 4,000 
                 4,049 
               
               
                   
                 4,050 
                 4,099 
               
               
                   
                 4,100 
                 4,149 
               
               
                   
                 4,150 
                 4,199 
               
               
                   
                 4,200 
                 4,249 
               
               
                   
                 4,250 
                 4,299 
               
               
                   
                 4,300 
                 4,349 
               
               
                   
                 4,350 
                 4,399 
               
               
                   
                 4,400 
                 4,449 
               
               
                   
                 4,450 
                 4,499 
               
               
                   
                 4,500 
                 4,549 
               
               
                   
                 4,550 
                 4,599 
               
               
                   
                 4,600 
                 4,649 
               
               
                   
                 4,650 
                 4,699 
               
               
                   
                 4,700 
                 4,749 
               
               
                   
                 4,750 
                 4,799 
               
               
                   
                 4,800 
                 4,849 
               
               
                   
                 4,850 
                 4,899 
               
               
                   
                 4,900 
                 4,949 
               
               
                   
                 4,950 
                 4,999 
               
               
                   
                 5,000 
                 5,049 
               
               
                   
                 5,050 
                 5,099 
               
               
                   
                 5,100 
                 5,149 
               
               
                   
                 5,150 
                 5,199 
               
               
                   
                 5,200 
                 5,249 
               
               
                   
                 5,250 
                 5,299 
               
               
                   
                 5,300 
                 5,349 
               
               
                   
                 5,350 
                 5,399 
               
               
                   
                 5,400 
                 5,449 
               
               
                   
                 5,450 
                 5,499 
               
               
                   
                 5,500 
                 5,549 
               
               
                   
                 5,550 
                 5,599 
               
               
                   
                 5,600 
                 5,649 
               
               
                   
                 5,650 
                 5,699 
               
               
                   
                 5,700 
                 5,749 
               
               
                   
                 5,750 
                 5,799 
               
               
                   
                 5,800 
                 5,849 
               
               
                   
                 5,850 
                 5,899 
               
               
                   
                 5,900 
                 5,949 
               
               
                   
                 5,950 
                 5,999 
               
               
                   
                 6,000 
                 6,049 
               
               
                   
                 6,050 
                 6,099 
               
               
                   
                 6,100 
                 6,149 
               
               
                   
                 6,150 
                 6,199 
               
               
                   
                 6,200 
                 6,249 
               
               
                   
                 6,250 
                 6,299 
               
               
                   
                 6,300 
                 6,349 
               
               
                   
                 6,350 
                 6,399 
               
               
                   
                 6,400 
                 6,449 
               
               
                   
                 6,450 
                 6,499 
               
               
                   
                 6,500 
                 6,549 
               
               
                   
                 6,550 
                 6,599 
               
               
                   
                 6,600 
                 6,649 
               
               
                   
                 6,650 
                 6,699 
               
               
                   
                 6,700 
                 6,749 
               
               
                   
                 6,750 
                 6,799 
               
               
                   
                 6,800 
                 6,849 
               
               
                   
                 6,850 
                 6,899 
               
               
                   
                 6,900 
                 6,949 
               
               
                   
                 6,950 
                 6,999 
               
               
                   
                 7,000 
                 7,049 
               
               
                   
                 7,050 
                 7,099 
               
               
                   
                 7,100 
                 7,149 
               
               
                   
                 7,150 
                 7,199 
               
               
                   
                 7,200 
                 7,249 
               
               
                   
                 7,250 
                 7,299 
               
               
                   
                 7,300 
                 7,349 
               
               
                   
                 7,350 
                 7,399 
               
               
                   
                 7,400 
                 7,449 
               
               
                   
                 7,450 
                 7,499 
               
               
                   
                 7,500 
                 7,549 
               
               
                   
                 7,550 
                 7,599 
               
               
                   
                 7,600 
                 7,649 
               
               
                   
                 7,650 
                 7,699 
               
               
                   
                 7,700 
                 7,749 
               
               
                   
                 7,750 
                 7,799 
               
               
                   
                 7,800 
                 7,849 
               
               
                   
                 7,850 
                 7,899 
               
               
                   
                 7,900 
                 7,949 
               
               
                   
                 7,950 
                 7,999 
               
               
                   
                 8,000 
                 &gt;8,000 
               
            
           
           
               
               
            
               
                   
                 Other suitable ranges 
               
               
                   
                   
               
            
           
         
       
     
     The first string and the second string may define a first CCT mixing circuit. The apparatus may include second CCT mixing circuits. Each of the second CCT mixing circuits may be arranged: (1) in parallel with the first CCT mixing circuit between (a) the hot conductor; and (b) the first and second neutral conductors; and (2) along an elongated substrate. 
     The apparatus may include a DC power supply. The apparatus may include a transmission line having the length. The length may extend from the DC power supply to the socket. 
     The DC power supply may be configured to provide a voltage to the transmission line. The transmission line may attenuate the voltage by an amount that is no more than a threshold number of volts. Table 19 lists illustrative threshold volts. 
     
       
         
           
               
             
               
                 TABLE 19 
               
             
            
               
                   
               
               
                 Illustrative threshold volts. 
               
               
                 Illustrative ranges of threshold volts 
               
               
                 Range 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 &lt;2 
                 2 
               
               
                   
                 2 
                 2.2 
               
               
                   
                 2.2 
                 2.4 
               
               
                   
                 2.4 
                 2.6 
               
               
                   
                 2.6 
                 2.8 
               
               
                   
                 2.8 
                 3 
               
               
                   
                 3 
                 3.2 
               
               
                   
                 3.2 
                 3.4 
               
               
                   
                 3.4 
                 3.6 
               
               
                   
                 3.6 
                 3.8 
               
               
                   
                 3.8 
                 4 
               
               
                   
                 4 
                 4.2 
               
               
                   
                 4.2 
                 4.4 
               
               
                   
                 4.4 
                 4.6 
               
               
                   
                 4.6 
                 4.8 
               
               
                   
                 4.8 
                 5 
               
               
                   
                 5 
                 5.2 
               
               
                   
                 5.2 
                 5.4 
               
               
                   
                 5.4 
                 5.6 
               
               
                   
                 5.6 
                 5.8 
               
               
                   
                 5.8 
                 6 
               
               
                   
                 6 
                 &gt;6 
               
               
                   
                 Other suitable 
                 Other suitable 
               
               
                   
                 ranges of 
                 ranges of 
               
               
                   
                 threshold 
                 threshold 
               
               
                   
                 volts 
                 volts 
               
               
                   
                   
               
            
           
         
       
     
     For a given threshold voltage, the length may be extended by increasing the transmission line conductor diameter (reducing the wire diameter). Table 19A lists illustrative wire diameters. 
     
       
         
           
               
             
               
                 TABLE 19A 
               
             
            
               
                   
               
               
                 Illustrative wire diameters. 
               
               
                 Illustrative wire diameters (mm) 
               
               
                 Range 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                   &lt;.08 
                 0.08 
               
               
                   
                 0.08 
                 0.09 
               
               
                   
                 0.09 
                 0.1 
               
               
                   
                 0.1 
                 0.11 
               
               
                   
                 0.11 
                 0.13 
               
               
                   
                 0.13 
                 0.14 
               
               
                   
                 0.14 
                 0.16 
               
               
                   
                 0.16 
                 0.18 
               
               
                   
                 0.18 
                 0.2 
               
               
                   
                 0.2 
                 0.23 
               
               
                   
                 0.23 
                 0.26 
               
               
                   
                 0.26 
                 0.29 
               
               
                   
                 0.29 
                 0.32 
               
               
                   
                 0.32 
                 0.36 
               
               
                   
                 0.36 
                 0.41 
               
               
                   
                 0.41 
                 0.46 
               
               
                   
                 0.46 
                 0.51 
               
               
                   
                 0.51 
                 0.57 
               
               
                   
                 0.57 
                 0.64 
               
               
                   
                 0.64 
                 0.72 
               
               
                   
                 0.72 
                 0.81 
               
               
                   
                 0.81 
                 0.91 
               
               
                   
                 0.91 
                 1.02 
               
               
                   
                 1.02 
                 1.15 
               
               
                   
                 1.15 
                 1.29 
               
               
                   
                 1.29 
                 1.45 
               
               
                   
                 1.45 
                 1.63 
               
               
                   
                 1.63 
                 1.83 
               
               
                   
                 1.83 
                 2.05 
               
               
                   
                 2.05 
                 2.31 
               
               
                   
                 2.31 
                 2.59 
               
               
                   
                 2.59 
                 2.91 
               
               
                   
                 2.91 
                 3.26 
               
               
                   
                 3.26 
                 3.67 
               
               
                   
                 3.67 
                 4.12 
               
               
                   
                 4.12 
                 4.62 
               
               
                   
                 4.62 
                 5.19 
               
               
                   
                 5.19 
                 5.83 
               
               
                   
                 5.83 
                 6.54 
               
               
                   
                 6.54 
                 7.35 
               
               
                   
                 7.35 
                 8.25 
               
               
                   
                 8.25 
                 9.27 
               
               
                   
                 9.27 
                 10.41 
               
               
                   
                 10.41 
                 11.68 
               
               
                   
                 11.68 
                 &gt;11.68 
               
               
                   
                 Other suitable 
                 Other suitable 
               
               
                   
                 ranges of 
                 ranges of 
               
               
                   
                 wire 
                 wire 
               
               
                   
                 diameters 
                 diameters 
               
               
                   
                   
               
            
           
         
       
     
     For a given threshold voltage, the length may be extended by decreasing the linear light-output density. Table 19B lists illustrative linear light-output densities. 
     
       
         
           
               
             
               
                 TABLE 19B 
               
             
            
               
                   
               
               
                 Illustrative linear light-output densities. 
               
               
                 Illustrative linear light-output  
               
               
                 densities (lumen/foot) 
               
               
                 Range 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 &lt;10 
                 10 
               
               
                   
                 10 
                 20 
               
               
                   
                 20 
                 30 
               
               
                   
                 30 
                 40 
               
               
                   
                 40 
                 50 
               
               
                   
                 50 
                 60 
               
               
                   
                 60 
                 70 
               
               
                   
                 70 
                 80 
               
               
                   
                 80 
                 90 
               
               
                   
                 90 
                 100 
               
               
                   
                 100 
                 110 
               
               
                   
                 110 
                 120 
               
               
                   
                 120 
                 130 
               
               
                   
                 130 
                 140 
               
               
                   
                 140 
                 150 
               
               
                   
                 150 
                 160 
               
               
                   
                 160 
                 170 
               
               
                   
                 170 
                 180 
               
               
                   
                 180 
                 190 
               
               
                   
                 190 
                 200 
               
               
                   
                 200 
                 210 
               
               
                   
                 210 
                 220 
               
               
                   
                 220 
                 230 
               
               
                   
                 230 
                 240 
               
               
                   
                 240 
                 250 
               
               
                   
                 250 
                 260 
               
               
                   
                 260 
                 270 
               
               
                   
                 270 
                 280 
               
               
                   
                 280 
                 290 
               
               
                   
                 290 
                 300 
               
               
                   
                 300 
                 &gt;300 
               
               
                   
                 Other suitable 
                 Other suitable 
               
               
                   
                 ranges of linear 
                 ranges of linear 
               
               
                   
                 light-output 
                 light-output 
               
               
                   
                 densities 
                 densities 
               
               
                   
                   
               
            
           
         
       
     
     For a threshold voltage of 4 VDC, with linear light density of 100 lumens/foot, and 20 AWG wire, a length of 100 ft. may be used. 
     The apparatus may include a user-adjustable CCT mixing circuit. The mixing circuit may be configured to allocate power from a DC power supply to the first LED emitter. The mixing circuit may be configured to allocate power from a DC power supply to the second LED emitter. 
     The mixing circuit may be configured to distribute power from the power supply between the first LED emitter and the second LED emitter. 
     The socket may be a mounted socket. The mounted socket may be configured to engage a free socket in: a first orientation relative to the mounted socket; and a second orientation relative to the mounted socket. The second orientation may be opposite the first orientation. 
     The socket may include first power rail contacts. The first power rail contacts may include a first hot contact. The first power rail contacts may include a first high coordinated color temperature (“CCT”) neutral contact. The first power rail contacts may include a first low CCT neutral contact. The socket may include second power rail contacts. The second power rail contacts may include a second hot contact. The second power rail contacts may include a second high CCT neutral contact. The second power rail contacts may include a second low CCT neutral contact. 
     The first and second power rail contacts may be disposed in a block. The block may define receptacles. Each of the first and second power rail contacts may be disposed in a different receptacle. The receptacles may define a number of rows. The receptacles may define a number of columns. Table 20 lists illustrative numbers of rows. 
     
       
         
           
               
             
               
                 TABLE 20 
               
               
                   
               
               
                 Illustrative numbers of rows. 
               
               
                 Illustrative 
               
               
                 numbers of rows 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 2 
               
               
                 3 
               
               
                 4 
               
               
                 5 
               
               
                 6 
               
               
                 Other suitable numbers of rows 
               
               
                   
               
            
           
         
       
     
     Table 21 lists illustrative numbers of columns. 
     
       
         
           
               
             
               
                 TABLE 21 
               
               
                   
               
               
                 Illustrative numbers of columns. 
               
               
                 Illustrative  
               
               
                 numbers of columns 
               
               
                   
               
             
            
               
                 2 
               
               
                 3 
               
               
                 4 
               
               
                 5 
               
               
                 6 
               
               
                 Other suitable numbers of columns 
               
               
                   
               
            
           
         
       
     
     The first and second hot contacts may be wired in parallel with each other. The first and second high CCT neutral contacts may be wired in parallel with each other. The first and second low CCT neutral contacts may be wired in parallel with each other. 
     The socket may have a central axis. The central axis may be normal to a plane defined by the receptacles. The second hot contact may be displaced 180°, about the central axis, from the first hot contact. The second high CCT neutral contact may be displaced 180°, about the central axis, from the first high CCT neutral contact. The second low CCT neutral contact may be displaced 180°, about the central axis, from the first low CCT neutral contact. 
     The emitter may be first emitter. The LED circuit may be a first LED circuit. The socket may be a first socket. The apparatus may include a second emitter. The apparatus may include a second LED circuit. The apparatus may include a second non-polar socket. The first emitter, the first LED circuit, and the first socket may define a first lighting circuit. The first light circuit may be disposed on a first lamina section. The second emitter, the second LED circuit, and the second socket may define a second lighting circuit. The second lighting circuit may be disposed on a second lamina section. A break-away joint may separably join the first and second lamina section. The first lighting circuit may be configured to transmit power and control information to the second lighting circuit. The first lighting circuit may be operable to provide light having an adjustable correlated color temperature when the second lamina section is joined to the first lamina section. The first lighting circuit may be operable to provide light having an adjustable correlated color temperature when the second lamina section is separated from the first lamina section. 
     The first lighting circuit may include a first LED circuit. The first lighting circuit may include a first LED emitter. The first lighting circuit may include a first power rail. The second lighting circuit may include a second LED circuit. The second lighting circuit may include a second LED emitter. The second lighting circuit may include a second power rail in electrical communication with the first power rail. 
     The apparatus may include a socket that includes a power rail jumper. The power rail jumper may be configured to bridge between a fixture support power rail and the first power rail. The apparatus may include a holder. The holder may be configured to hold a lamina section to a fixture support. 
     Illustrative embodiments of apparatus and methods in accordance with the principles of the invention will now be described with reference to the accompanying drawings, which form a part hereof. It is to be understood that other embodiments may be utilized and that structural, functional and procedural modifications or omissions may be made without departing from the scope and spirit of the present invention. 
     Some embodiments may omit features shown and/or described in connection with the illustrative apparatus. Some embodiments may include features that are neither shown nor described in connection with the illustrative apparatus. Features of illustrative apparatus may be combined. For example, one illustrative embodiment may include features shown in connection with another illustrative embodiment. 
     Embodiments may involve some or all of the features of the illustrative apparatus and/or some or all of the steps of the methods associated therewith. 
       FIG.  1    schematically illustrates a computing server such as  101  (alternatively referred to herein as a “server or computer”) that may be used in accordance with the principles of the invention. The server  101  may have a processor  103  for controlling overall operation of the server and its associated components, including RAM  105 , ROM  107 , input/output (“I/O”) module  109 , and memory  115 . 
     I/O module  109  may include a microphone, keypad, touchscreen and/or stylus through which a user of server  101  may provide input, and may also include one or more of a speaker for providing audio output and a video display device for providing textual, audiovisual and/or graphical output. Software may be stored within memory  115  and/or other storage (not shown) to provide instructions to processor  103  for enabling server  101  to perform various functions. For example, memory  115  may store software used by server  101 , such as an operating system  117 , application programs  119 , and an associated database  111 . Alternatively, some or all of computer executable instructions of server  101  may be embodied in hardware or firmware (not shown). 
     Server  101  may operate in a networked environment supporting connections to one or more remote computers, such as terminals  141  and  151 . Terminals  141  and  151  may be personal computers or servers that include many or all of the elements described above relative to server  101 . The network connections depicted in  FIG.  1    include a local area network (LAN)  125  and a wide area network (WAN)  129 , but may also include other networks. 
     When used in a LAN networking environment, server  101  is connected to LAN  125  through a network interface or adapter  113 . 
     When used in a WAN networking environment, server  101  may include a modem  127  or other means for establishing communications over WAN  129 , such as Internet  131 . 
     It will be appreciated that the network connections shown are illustrative and other means of establishing a communications link between the computers may be used. The existence of any of various well-known protocols such as TCP/IP, Ethernet, FTP, HTTP and the like is presumed, and the system may be operated in a client-server configuration to permit a user to retrieve web pages from a web-based server. Any of various conventional web browsers may be used to display and manipulate data on web pages. 
     Additionally, application program  119 , which may be used by server  101 , may include computer executable instructions for invoking user functionality related to communication, such as email, short message service (SMS), and voice input and speech recognition applications. 
     Computing server  101  and/or terminals  141  or  151  may also be mobile terminals including various other components, such as a battery, speaker, and antennas (not shown). Terminal  151  and/or terminal  141  may be portable devices such as a laptop, tablet, smartphone or any other suitable device for receiving, storing, transmitting and/or displaying relevant information. 
     Any information described above in connection with database  111 , and any other suitable information, may be stored in memory  115 . One or more of applications  119  may include one or more algorithms that may be used to perform the functions of one or more of a fixture arrangement, or any component thereof, a fixture control module, or any component thereof, and an input, or any component thereof, and perform any other suitable tasks. 
     The apparatus and methods may be operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with the invention include, but are not limited to, personal computers, server computers, hand-held or laptop devices, tablets, mobile phones and/or other personal digital assistants (“PDAs”), multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. 
     The apparatus and methods may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices. 
       FIG.  2    shows an illustrative apparatus such as  200  that may be configured in accordance with the principles of the invention. 
     Apparatus  200  may be a computing machine. Apparatus  200  may include one or more features of the apparatus that is shown in  FIG.  1   . 
     Apparatus  200  may include chip module  202 , which may include one or more integrated circuits, and which may include logic configured to perform any other suitable logical operations. 
     Apparatus  200  may include one or more of the following components: I/O circuitry  204 , which may include a transmitter device and a receiver device and may interface with fiber optic cable, coaxial cable, telephone lines, wireless devices, PHY layer hardware, a keypad/display control device or any other suitable encoded media or devices; peripheral devices  206 , which may include counter timers, real-time timers, power-on reset generators or any other suitable peripheral devices; logical processing device  208 , which may perform functions of one or more of a fixture arrangement, or any component thereof, a fixture control module, or any component thereof, and an input, or any component thereof, and perform any other suitable tasks or other methods described herein; and machine-readable memory  210 . 
     Machine-readable memory  210  may be configured to store in machine-readable data structures information of one or more of a fixture arrangement, or any component thereof, a fixture control module, or any component thereof, and an input, or any component thereof, and any other suitable information or data structures. 
     Components  202 ,  204 ,  206 ,  208  and  210  may be coupled together by a system bus or other interconnections  212  and may be present on one or more circuit boards such as  220 . In some embodiments, the components may be integrated into a single chip. 
     The chip may be silicon-based. 
       FIG.  3    shows illustrative architecture  300  for controlling fixtures. Architecture  300  may include fixture arrangement  302 . Architecture  300  may include fixture control module  304 . Architecture  300  may include inputs  306 . Architecture  300  may include wide area network  308 . Architecture  300  may define one or more network segments. A first segment may include inputs  306 . A second segment may include fixtures such as  316  and  318  in fixture arrangement  302 . 
     A segment may include one or more individually addressable devices. A segment may include one or more addressable groups. 
     Fixture arrangement  302  may include fixture support  310 . Fixture arrangement  302  may be supported by mount M. Mount M may fix fixture support  310  to structure S. Structure S may include a ceiling, a wall, a beam, cabinet, a free-standing object or any other suitable structure. Fixture support  310  may support one or more fixtures such as fixture  316 . Fixture support  310  may support one or more fixtures such as fixture  318 . One or more of fixtures  316  and  318  may be disposed on top of fixture support  310 . One or more of fixtures  316  and  318  may be disposed on bottom of fixture support  310 . One or more of fixtures  316  and  318  may be disposed on a side of fixture support  310 . One or more of fixtures  316  and  318  may be disposed on an end of fixture support  310 . 
     Fixture control module  304  may include fixture controller  320 . Fixture control module  304  may include user interface  322 . Fixture control module  304  may include receptacle  324 . Fixture controller  320  may be in electrical communication with line power  326 . Line power  326  may provide two-phase or three-phase power at 110 V or 220 V, DC voltage at any suitable level, or any other suitable voltage. Receptacle  324  may receive a dimmer voltage from electronic dimmer  330 . Fixture  316  may operate over a range of operational levels. Fixture  316  may operate at a maximum operational level. The dimmer voltage may have a maximum voltage. A proportion of the maximum dimmer voltage that is represented by the dimmer voltage may correspond to an operational level at which a fixture  316  is to be operated. The dimmer voltage proportion, if applied to the maximum operational level, may define the operational level at which a fixture  316  is to be operated. 
     The operational level may be a power level, a current level, or any other suitable level. 
     Input  306  may include user communication device  328 . Input  306  may include electronic dimmer  330 . 
     Fixture controller  320  may include one or more elements of apparatus shown in  FIG.  1  or  2   . 
     Fixture controller  320  may be in wired electrical communication with fixture arrangement  302 . The wired electrical communication may be provided by cable  317 . The wired electrical communication may provide power to fixture arrangement  302 . The wired electrical communication may provide control messages to fixture arrangement  302 . Fixture controller  320  may provide the power and the control messages over different conductors. Fixture controller  320  may provide the power and the control messages simultaneously over a conductor, as is done in power line control methods. 
     Fixture controller  320  may be in wireless communication with fixture arrangement  302 . The wireless electrical communication may provide control messages to fixture arrangement  302 . 
     Communication between fixture controller  320  and fixture arrangement  302  may be wholly or in part by wired electrical communication. Communication between fixture controller  320  and fixture arrangement  302  may be wholly or in part by wireless electrical communication. Communication between fixture controller  320  and fixture arrangement  302  may be wholly or in part by wireless communication. The wireless communication may include optical communication. The wireless communication may include acoustic communication. Communication between fixture controller  320  and fixture arrangement  302  may be partially by wired electrical communication and partially wireless communication. 
     Fixture control module  304  may be in communication with input  306 . 
     User interface  322  may provide communication functions for fixture control module  304 . The communication may include transmission of a user command to fixture control module  304 . The communication may include transmission of fixture information to input  306 . The fixture information may include a fixture parameter. The communication may be wireless. The communication may be wired. 
     User interface  322  may receive a user command from communication device  328 . User interface  322  may include a data input device. The data input device may include one or more of a touch screen, a key pad and any other suitable device. User interface  322  may receive a user command from communication device  328 . User communication device  328  may include one or more of the elements shown in  FIG.  1  or  2   . Control over a fixture may be passed from user communication device  328  to user interface  322 . Control over a fixture may be passed from user interface  322  to user communication device  328 . The control may be passed by the user. The control may be configured to be passed automatically. The control may be configured to be passed automatically upon the fulfilment of a condition. The condition may be a temporal condition. The condition may be based on a fixture parameter. The condition may be based on an ambient lighting condition. The condition may be based on any suitable condition. 
     Electronic dimmer  330  may provide Triac/ELV dimming. Electronic dimmer  330  may receiver electrical current from line power  332 . 
     Arrangement  100  may include one or more sensors. The sensors may include a range sensor such as  334  and  336 . The range sensor may sense a distance to a surface. The sensors may include a temperature sensor such as  338  and  340 . The temperature sensor may sense an ambient temperature. The temperature sensor may sense a temperature or a differential temperature of a surface at a distance from the sensor. The sensors may include a motion sensors such as  342 . The sensors may include one or more light sensors such as  344 . The light sensor may sense visible light. The light sensor may sense energy associated with one or more wavelengths of light. 
       FIG.  4    shows illustrative communications  400  between fixture controller  320  and input  306 . Illustrative communications  400  may include user command  402 , fixture information  404 , dimmer voltage  406 , dimmer feedback  408  or any other suitable communication. 
       FIG.  4    shows illustrative communications  410  between fixture controller  320  and fixture arrangement  302 . Communications  410  may include control messages  412  for control performance of fixtures such as  316 . Communications  410  may include fixture parameter  414 . 
       FIG.  5    shows illustrative architecture  500  for controlling fixtures. Architecture  500  may have one or more features in common with architecture  300  (shown in  FIG.  3   ). Architecture  500  may include fixture arrangement  502 . Architecture  500  may include fixture control module  504 . Architecture  500  may include inputs  506 . 
     Fixture arrangement  502  may include one or more fixture supports such as fixture support  508 . Fixture support  508  may provide mechanical to support to one or more fixtures such as fixture  510 . Fixture support  508  may convey electrical power from control module  504  to one or more fixtures such as fixture  510 . Fixture support  508  may convey electrical signals from control module  504  to one or more fixtures such as fixture  510 . 
     Fixture  510  may include power block  512 . Power block  512  may receive electrical power from fixture support  508 . Power block  512  may receive current from fixture support  508 . The current may include DC current. The current may include AC current. Power block  512  may receive the current at a voltage. The voltage may be 48 V. Table 22 lists illustrative ranges that may include the voltage. 
     
       
         
           
               
             
               
                 TABLE 22 
               
             
            
               
                   
               
               
                 Illustrative voltage ranges. 
               
               
                 Illustrative voltage ranges 
               
               
                 (V) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 5 
               
               
                   
                 5 
                 10 
               
               
                   
                 10 
                 15 
               
               
                   
                 15 
                 20 
               
               
                   
                 20 
                 25 
               
               
                   
                 25 
                 30 
               
               
                   
                 30 
                 35 
               
               
                   
                 35 
                 40 
               
               
                   
                 40 
                 45 
               
               
                   
                 45 
                 50 
               
               
                   
                 50 
                 55 
               
               
                   
                 55 
                 60 
               
               
                   
                 60 
                 &gt;60 
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper 
               
               
                   
                 limits 
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     Power block  512  may provide output voltage to components of fixture  510 . The output may include an AC voltage. The output may include a DC voltage. Power block  512  may provide different output voltages to different components of fixture  510 . Table 23 lists illustrative output voltage ranges that may include the output voltage. 
     
       
         
           
               
             
               
                 TABLE 23 
               
             
            
               
                   
               
               
                 Illustrative output voltage ranges. 
               
               
                 Illustrative voltage ranges 
               
               
                 (V) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 0 
                 5 
               
               
                   
                 5 
                 10 
               
               
                   
                 10 
                 15 
               
               
                   
                 15 
                 20 
               
               
                   
                 20 
                 25 
               
               
                   
                 25 
                 30 
               
               
                   
                 30 
                 35 
               
               
                   
                 35 
                 40 
               
               
                   
                 40 
                 45 
               
               
                   
                 45 
                 50 
               
               
                   
                 50 
                 55 
               
               
                   
                 55 
                 60 
               
               
                   
                 60 
                 &gt;60 
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper  
               
               
                   
                 limits 
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     The output voltage may be a step-down from 48 VDC to 5 VDC. The output voltage may be a step-down from 48 VDC to 3.3 VDC. 
     Fixture  510  may include transceiver  514 . Transceiver  514  may receive electrical signals from fixture support  508 . Transceiver  514  may receive electrical power from power block  512 . The electrical power may include AC power. The electrical power may include DC power. Transceiver  514  may exchange communications  410  with fixture support  508 . Transceiver  514  may exchange communications  410  with device control module  516 . 
     Fixture  510  may include one or more device control modules such as device control module (“DCM”)  516 . Fixture  510  may include a device control module for each of one or more devices in fixture  510 . Device control module  516  may receive electrical signals from transceiver  514 . Device control module  516  may receive electrical power from power block  512 . Device control module  516  may include a microprocessor. Device  518  may receive electrical signals from device control module  516 . The electrical signals may cause device  518  to change a fixture parameter. 
     Table 24 lists illustrative functions of device control module  516 . 
     
       
         
           
               
             
               
                 TABLE 24 
               
               
                   
               
               
                 Illustrative functions of device control module 516. 
               
               
                 Illustrative functions of device control module 516 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Manage fixture behaviors during power on 
               
               
                 Reset based on detection of segment control module (“SCM”) 524 
               
               
                 Receive control messages such as 412 from segment control module 524 
               
               
                 Execute instructions in control messages such as 412 
               
               
                 Transmit fixture parameters such as 414 to segment control module 524 
               
               
                 Respond to requests from segment control module 524 for fixture status 
               
               
                 Other suitable functions 
               
               
                   
               
            
           
         
       
     
     Table 25 lists illustrative resources with which control module  516  may interface. 
     
       
         
           
               
             
               
                 TABLE 25 
               
               
                   
               
               
                 Illustrative resources. 
               
               
                 Illustrative resources 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Segment control module 524 
               
               
                 Other suitable resources 
               
               
                   
               
            
           
         
       
     
     Fixture control module  504  may include fixture controller  520 . Fixture control module may include power unit  522 . 
     Fixture controller  520  may include segment control module  524 . Fixture controller module  520  may include user interface  526 . Fixture controller  520  may include transceiver  530 . Fixture controller  520  may include a Wifi module such as  528 . Fixture controller  520  may include power block  532 . 
     Segment control module  524  may manage one or more network segments. A network segment may include a network of device control modules such as  516 . Table 26 lists illustrative functions of segment control module  524 . 
     
       
         
           
               
             
               
                 TABLE 26 
               
               
                   
               
               
                 Illustrative functions of segment control module 524. 
               
               
                 Illustrative functions of segment control module 524 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Manage the network of device control modules such as 516 
               
               
                 Manage and maintaining the groups of devices such as 518 defined for the network. 
               
               
                 Receive inputs from inputs 506. 
               
               
                 Translate inputs from inputs 506 into control messages 412 
               
               
                 Translate inputs from inputs 506 into Wifi module 528 inputs 
               
               
                 Manage interface(s) connected to a modular interface connector in user interface 526 
               
               
                 Provide network and device updates to Wifi module 528 
               
               
                 Manage addition of devices to network 
               
               
                 Manage removal of devices from network 
               
               
                 Other suitable functions 
               
               
                   
               
            
           
         
       
     
     Table 27 lists illustrative interfaces that segment control module  524  may manage. 
     
       
         
           
               
             
               
                 TABLE 27 
               
               
                   
               
               
                 Illustrative interfaces. 
               
               
                 Illustrative interfaces 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 IoT Module 
               
               
                 Device Control Module 
               
               
                 0-10 V 
               
               
                 Triac/ELV Interface 
               
               
                 Modular I/O-DALI 
               
               
                 Modular I/O-DMX 
               
               
                 Modular I/O-Multiple 0-10 V inputs 
               
               
                 Other suitable interfaces 
               
               
                   
               
            
           
         
       
     
     Wifi module  528  may manage communications with channels  548  of input  506 . Table 28 lists illustrative functions of Wifi module  528 . 
     
       
         
           
               
             
               
                 TABLE 28 
               
               
                   
               
               
                 Illustrative functions of Wifi module 528. 
               
               
                 Illustrative functions of Wifi module 528 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Manage cloud connectivity (e.g., keeping cloud resources synchronized with current 
               
               
                 fixture parameters; receiving user commands from inputs 534; dispatching user commands 
               
               
                 received from the inputs 534 to segment control module 524). 
               
               
                 Advertise availability on a network of devices such as 518 for use by 3rd 
               
               
                 party systems (MDNS (multicast DNS), 
               
               
                 SDDP (Simple Device Discovery Protocol) associated with inputs 534 etc.) 
               
               
                 Manage interactions with devices associated with inputs 534 
               
               
                 Manage connectivity with wireless remote controls 
               
               
                 (identify remote controls that are included in inputs 534) 
               
               
                 Manage update of firmware (e.g., on 516, 524, 528, 544) 
               
               
                 Manage scheduled actions 
               
               
                 Other suitable functions 
               
               
                   
               
            
           
         
       
     
     Table 29 lists illustrative resources with which Wi-Fi module  528  may interface. 
     
       
         
           
               
             
               
                 TABLE 29 
               
               
                   
               
               
                 Illustrative resources. 
               
               
                 Illustrative resources 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Segment control module 524 
               
               
                 Local IP devices (e.g., Control 4) 
               
               
                 Fixture controllers other than fixture controller 520, and having one or more 
               
               
                 features in common with fixture controller 520 
               
               
                 Cloud resources 
               
               
                 Devices associated with inputs 534 
               
               
                 Other suitable resources 
               
               
                   
               
            
           
         
       
     
     Table 30 lists illustrative message types for communications between segment control module  524  and Wi-Fi module  528 . 
     
       
         
           
               
             
               
                 TABLE 30 
               
             
            
               
                   
               
               
                 Illustrative message types for communications between 
               
               
                 segment control module 524 and Wi-Fi module 528. 
               
               
                 Illustrative SCM-WIFI Module communications 
               
            
           
           
               
               
            
               
                 Instruction(s) 
                 Argument(s) 
               
               
                   
               
               
                 NODE_GET_PARAM 
                   
               
               
                  WIFI Module to SCM 
                 Fixture Address 
               
               
                  SCM to WIFI Module 
                  Data structure containing fixture parameters 
               
               
                   
                  Device, general 
               
               
                   
                  Device index 
               
               
                   
                  Acknowledge or Failure Code 
               
               
                   
                  Value contains static and dynamic parameter 
               
               
                   
                  Value contains only dynamic parameter. 
               
               
                   
                  Device ID 
               
               
                   
                  YYYYMMDD (BCD) 
               
               
                   
                  Factory list 
               
               
                   
                  Model number 
               
               
                   
                  Led driver model number 
               
               
                   
                  Rate current output 
               
               
                   
                  Percentage of customize current level (0.01%) 
               
               
                   
                  PCB version (ASCII) 
               
               
                   
                  Firmware: minor version, major version (BCD) 
               
               
                   
                  Communication protocol version: minor version, major 
               
               
                   
                  version (BCD) 
               
               
                   
                   Light 
               
               
                   
                  Pointer to respond list 
               
               
                   
                  On/Off: 0: off, 1: on. 
               
               
                   
                  Dimming curve mode, 0: linear, 1: logarithm. 
               
               
                   
                  Soft on fade rate(s). 0: disable, 0xFF: invalid function 
               
               
                   
                  Fade to black rate(s). 0: disable, 0xFF: invalid function 
               
               
                   
                  Initial status level (0.01%) (power on) 
               
               
                   
                  Color temperature mix level, (0.01%) 
               
               
                 NODE_CONTROL 
                 Luminance level, (0.01%) 
               
               
                  WIFI Module to SCM 
                  Channel number: ( m &lt;= 12) Address and Command 
               
               
                   
                  Index 0 
               
               
                  SCM to WIFI Module 
                  Channel 0, dimming level (0.01%) Acknowledgement or 
               
               
                   
                  Failure Code 
               
               
                   
                  Index m 
               
               
                   
                  Channel m, dimming level (0.01%) 
               
               
                   
                   STM32 
               
               
                   
                  Device0 ID 
               
               
                   
                  Device1 ID 
               
               
                   
                  ... 
               
               
                   
                  DeviceN ID 
               
               
                   
                   Motion Senso 
               
               
                   
                  Pointer to respond list 
               
               
                   
                  On/Off, 0 = off. 1 = on. 
               
               
                   
                  Product lifetime (hour) 
               
               
                   
                  Trigger state, 0 = no trigger, 1 = triggered. 
               
               
                   
                  Sensitivity level. 
               
               
                   
                  Range of detection (feet) 
               
               
                   
                  Standby time(s) 
               
               
                   
                   Daylight sensor 
               
               
                   
                  Pointer to respond list 
               
               
                   
                  On/Off, 0 = off. 1 = on. 
               
               
                   
                  Trigger state, 0 = no trigger, 1 = triggered. 
               
               
                   
                  Sensitivity level 
               
               
                   
                  Product lifetime (hour) 
               
               
                   
                   Motorlight 
               
               
                   
                  Pointer to Respond List 
               
               
                   
                  On/Off, 0 = off. 1 = on. 
               
               
                   
                  Dimming curve mode, 0 = linear. 1 = logarithm. 
               
               
                   
                  Product lifetime 
               
               
                   
                  Soft on fade rate(s). 0 = disable, 0xFF = invalid function. 
               
               
                   
                  Fade to black rate(s). 0 = disable, 0xFF = invalid function 
               
               
                   
                  Initial status level (0.01%) 
               
               
                   
                  Color temperature mix level, (0.01%) 
               
               
                   
                  Luminance level, (0.01%) 
               
               
                   
                  Axis, 7: up, 6: down, 5: left, 4: right. 
               
               
                   
                  Lens, (0.01%) 
               
               
                   
                  Channel number(m &lt;= 12) 
               
               
                   
                  Index0 
               
               
                   
                  Channel 0, dimming level (0.01%) 
               
               
                   
                  Index m 
               
               
                   
                  Channel m, dimming level (0.01%) 
               
               
                 CREATE GROUP 
                   
               
               
                  WIFI Module to SCM 
                 Create New Group 
               
               
                  SCM to WIFI Module 
                 Address for the newly requested group 
               
               
                 GROUP CONTROL 
                   
               
               
                  WIFI Module to SCM 
                 Group Address and Command 
               
               
                  SCM to WIFI Module 
                 Acknowledgement or Failure Code 
               
               
                 SET FIXTURE PARAMETER 
                   
               
               
                  WIFI Module to SCM 
                 Device ID 
               
               
                   
                 Value 
               
               
                   
                 On/Off: 0: off, 1: on. 
               
               
                   
                 Dimming curve mode, 0: linear, 1: logarithm. 
               
               
                   
                 Soft on fade rate(s). 0: disable, 0xFF: invalid function 
               
               
                   
                 Fade to black rate(s). 0:disable, 0xFF:invalid function 
               
               
                   
                 Initial status level scale = 0.01% 
               
               
                   
                 Luminance level scale = 0.01% 
               
               
                   
                 Color temperature mix level scale = 0.01% 
               
               
                   
                 Dimming channel (RED) Scale = 0.01% 
               
               
                   
                 Dimming channel (GREEN) Scale = 0.01% 
               
               
                   
                 Dimming channel (BLUE) Scale = 0.01% 
               
               
                   
                 Dimming channel (WHITE) scale = 0.01% 
               
               
                   
                 Dimming channel (COOL) scale = 0.01% 
               
               
                   
                 Dimming channel (WARM) scale = 0.01% 
               
               
                   
                 Sensitivity level. 
               
               
                   
                 Range of detection (feet) 
               
               
                   
                 Standby time(s) 
               
               
                   
                 Motor light Axis 
               
               
                   
                 Motor light Lens 
               
               
                  SCM to WIFI Module 
                 1: Successful 
               
               
                   
                 0: Fail 
               
               
                 NODE ADD 
                   
               
               
                  WIFI Module to SCM 
                 0: Add all device 
               
               
                   
                 2: Add motion 
               
               
                   
                 3: Add motor 
               
               
                   
                 4: Add daylight 
               
               
                   
                 5: Add light 
               
               
                  SCM to WIFI Module 
                 1: Successful 
               
               
                   
                 0: Fail 
               
               
                 NODE DELETE 
                   
               
               
                  WIFI Module to SCM 
                 Device ID 
               
               
                  SCM to WIFI Module 
                 Acknowledgement or Failure Code 
               
               
                 NODE OTA (Over the Air (firmware 
                   
               
               
                 update)) READY 
                   
               
               
                  WIFI Module to SCM 
                 Device ID 
               
               
                  SCM to WIFI Module 
                 1: Successful 
               
               
                   
                 0: Fail 
               
               
                 NODE OTA FIRMWARE INFO 
                   
               
               
                  WIFI Module to SCM 
                 Device ID 
               
               
                   
                 Packet number 
               
               
                   
                 Checksum entire firmware updated 
               
               
                  SCM to WIFI Module 
                 Successful 
               
               
                   
                 0: Fail 
               
               
                 SEND NODE FIRMWARE 
                   
               
               
                 PACKET TO SCM 
                   
               
               
                  WIFI Module to SCM 
                 ID 
               
               
                   
                 Packet index 
               
               
                   
                 Firmware data 
               
               
                  SCM to WIFI Module 
                 1: Successful 
               
               
                   
                 0: Fail 
               
               
                 NODE OTA FINISH 
                   
               
               
                  WIFI Module to SCM 
                 ID 
               
               
                  SCM to WIFI Module 
                 1: Successful 
               
               
                   
                 0: Fail 
               
               
                 RESET 
                   
               
               
                  WIFI Module to SCM 
                 1: Factory reset 
               
               
                   
                 0: Common reset 
               
               
                  SCM to WIFI Module 
                 1: Successful 
               
               
                   
                 0: Fail 
               
               
                   
               
            
           
         
       
     
     Architecture  500  may be an architecture in which some or all communications between segment control module  524  and Wi-Fi module  528  are initiated by Wi-Fi module  528 . 
     Architecture  500  may be an architecture in which some or all communications between segment control module  524  and Wi-Fi module  528  are initiated by segment control module  524 . 
     Transceiver  530  may receive communications  410  from segment control module  524 . Transceiver  530  may transmit communications  410  to fixture support  508 . Transceiver  530  may receive power from power block  532 . 
     Power block  532  may receive current from control power unit  522 . The current may include DC current. The current may include AC current. Power block  532  may receive the current at a voltage. The voltage may be 48 V. Table 31 lists illustrative ranges that may include the voltage. 
     
       
         
           
               
             
               
                 TABLE 31 
               
             
            
               
                   
               
               
                 Illustrative voltage ranges. 
               
               
                 Illustrative voltage ranges 
               
               
                 (V) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
               
                   
                  0 
                  5 
               
               
                   
                  5 
                 10 
               
               
                   
                 10 
                 15 
               
               
                   
                 15 
                 20 
               
               
                   
                 20 
                 25 
               
               
                   
                 25 
                 30 
               
               
                   
                 30 
                 35 
               
               
                   
                 35 
                 40 
               
               
                   
                 40 
                 45 
               
               
                   
                 45 
                 50 
               
               
                   
                 50 
                 55 
               
               
                   
                 55 
                 60 
               
               
                   
                 60 
                 &gt;60  
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper 
               
               
                   
                 limits 
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     Power block  532  may provide output voltage to components of fixture controller  520 . The output may include an AC voltage. The output may include a DC voltage. Power block  532  may provide different output voltages to different components of fixture  510 . Table 32 lists illustrative output voltage ranges that may include the output voltage. 
     
       
         
           
               
             
               
                 TABLE 32 
               
             
            
               
                   
               
               
                 Illustrative output voltage ranges. 
               
               
                 Illustrative voltage ranges 
               
               
                 (V) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
               
                   
                  0 
                  5 
               
               
                   
                  5 
                 10 
               
               
                   
                 10 
                 15 
               
               
                   
                 15 
                 20 
               
               
                   
                 20 
                 25 
               
               
                   
                 25 
                 30 
               
               
                   
                 30 
                 35 
               
               
                   
                 35 
                 40 
               
               
                   
                 40 
                 45 
               
               
                   
                 45 
                 50 
               
               
                   
                 50 
                 55 
               
               
                   
                 55 
                 60 
               
               
                   
                 60 
                 &gt;60  
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper 
               
               
                   
                 limits 
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     The output voltage may be a step-down from 48 VDC to 12 VDC. The output voltage may be a step-down from 48 VDC to 5 VDC. The output voltage may be a step-down from 48 VDC to 3.3 VDC. 
     User interface  526  may include Triac/ELV interface  536 . User interface  526  may include 0-10 V interface  538 . User interface  526  may include modular interface connector  540 . User interface  526  may include DMX module  544 . 
     Triac/ELV interface  536  may include a receptacle for a Triac/ELV connector. 
     0-10 V interface  538  may include a receptacle for a 0-10 V connector. 
     Modular interface  540  may include a receptacle for a modular interface connector. 
     DMX module  544  may include a microprocessor. DMX module  544  may include a receptacle for a DMX connector. 
     Interface  526  may include one or more sockets (not shown in  FIG.  5   ). A socket may receive a cartridge. The cartridge may include one or more of the receptacles. Each receptacle may be configured to mate with a connector corresponding to an input  506 . The cartridge may be insertable in, and removable from, the socket by the user. The cartridge may include terminals that match corresponding terminals in the socket. The socket may be used to receive signals from different inputs  506  in conjunction with a corresponding cartridge that is configured to mate with the desired input  506  and with interface  526 . 
     Inputs  534  may include control system  550 , such as those available under the tradenames Savant (available from Savant Systems, Inc., Hyannis, Mass.), Lutron (available from Lutron Electronics Co., Inc., Coopersburg, Pa.), Crestron (available from Crestron Electronics, Inc., Rockleigh, N.J.), Control4 (available from Wirepath Home Systems, LLC, dba Control4, Salt Lake city, Utah) and others. 
     Inputs  534  may include mobile app  552 , such as a mobile app available in conjunction with operating systems available under the tradenames Android (associated with the Open Handset Alliance, Mountainview, Calif.) and iOS (available from Apple Inc., Cupertino, Calif.) and others. 
     Inputs  534  may include communication from AWS IoT Core 554 (available from Amazon Web Services, Inc, Seattle, Wash.). 
     Inputs  534  may include other fixture controllers  556 . Fixture controllers of other fixtures controllers  556  may have one or more features in common with fixture controller  520 . 
     Inputs  534  may include remote control  558 . Remote control  558  may include a wall control. Remote control  558  may include one or more devices that communicate under a Bluetooth protocol. The Bluetooth protocol may be a Bluetooth LE protocol. 
     One or more of inputs  534  may be in communication with WIFI module  524  under a RESTful web service protocol. 
     Inputs  506  may include Triac/ELV unit  560 . 
     Inputs  506  may include 0-10V connector  562 . 
     Inputs  506  may include DMX controller  564 . 
     Inputs  506  may include user activation input  566 . User activation input  566  may include key-activation, touch-screen activation, contact-free interaction or any other suitable user activation input. 
     Inputs  506  may include keypad  542 . Keypad  542  may include a display. Keypad  542  may include keys. Keypad  542  may include a touchscreen. 
     Power unit  522  may include transformer  546 . Transformer  546  may receive power from power line LP. Powerline LP may provide 120 VAC, 220 VAC, or any other suitable power. 
     Transformer  546  may provide output power to fixture arrangement  502 . Transformer  546  may provide output power to fixture controller  520 . The output power may include an AC voltage. The output may include a DC voltage. Transformer  546  may provide different output power to different destinations, such as fixture arrangement  502 , fixture controller  520 , or an auxiliary destination. Table 33 lists illustrative output voltage ranges that may include an output voltage of transformer  546 . 
     
       
         
           
               
             
               
                 TABLE 33 
               
             
            
               
                   
               
               
                 Illustrative output voltage ranges. 
               
               
                 Illustrative voltage ranges 
               
               
                 (V) 
               
            
           
           
               
               
               
            
               
                   
                 Lower 
                 Upper 
               
               
                   
                   
               
               
                   
                  0 
                  5 
               
               
                   
                  5 
                 10 
               
               
                   
                 10 
                 15 
               
               
                   
                 15 
                 20 
               
               
                   
                 20 
                 25 
               
               
                   
                 25 
                 30 
               
               
                   
                 30 
                 35 
               
               
                   
                 35 
                 40 
               
               
                   
                 40 
                 45 
               
               
                   
                 45 
                 50 
               
               
                   
                 50 
                 55 
               
               
                   
                 55 
                 60 
               
               
                   
                 60 
                 &gt;60  
               
               
                   
                 Other 
                 Other 
               
               
                   
                 suitable 
                 suitable 
               
               
                   
                 lower 
                 upper 
               
               
                   
                 limits 
                 limits 
               
               
                   
                   
               
            
           
         
       
     
     The output voltage of transformer  546  may be a step-down from 120 VAC or 220 VAC to 48 VDC. 
     Communications such as  410  between segment control module  524  and device control module  516  may be transmitted along a bus. The bus may be a conductor. The conductor may connect segment control module  524  and device control module  516 . Communications  410  may conform to a bus protocol. 
     Segment control module  524  may manage one or more groups of fixtures. 
     A group may include one, two or more fixtures. The group may be managed by The segment control module may manage one, two or more groups. The fixtures in a group may be controlled together as one entity. A group will may be represented as a single network address. The address may be recognized on a segment. The segment control module may communicate with the fixtures of a group using a multicast networking approach. 
     The segment control module may notify a fixture when the fixture has been added to a group. The segment control module may notify a fixture when the fixture has been registered to a network address of the group. The device control unit of a fixture in a group may be programmed to act on all control messages that are addressed to the group network address. The segment control module may notify a fixture when the fixture has been removed from a group. The segment control module may notify a fixture when the fixture has been de-registered from a network address of the group. The device control unit of a fixture that is not in a group may be programmed, e.g., by default, to not act on control messages that are addressed to the group network address. 
     Architecture  500  may include one, two or more fixture control modules such as fixture control module  504 . The fixture control modules may be in a single location. The fixture control modules may be in different locations. Two or more fixture control modules that are connected to the same OSI Layer 2 network may be considered to be in the same location. 
     A command that sets the state of one or more fixtures in a location may be considered a “scene.” Within a scene, fixture parameters of all fixtures may be set independently of other fixtures in the scene. Architecture  500  may support  200  scenes, or more, or less, in a location. A scene may be defined to include fixtures associated with one or more fixture control modules such as  520 . 
     A scene may be used to effect a group when fixtures in different segments are desired to be managed as if they were in a single-segment group. 
     Table 34 lists illustrative address-related communications between segment control module  524  and device control module  516 . 
     
       
         
           
               
             
               
                 TABLE 34 
               
             
            
               
                   
               
               
                 Illustrative address-related communications between segment 
               
               
                 control module 524 and device control module 516. 
               
               
                 ADDRESS 
               
            
           
           
               
               
            
               
                 Instruction(s) 
                 Argument(s) 
               
               
                   
               
               
                 Set the DCM to generate a random 
                   
               
               
                 number and delay, then reply once 
                   
               
               
                  SCM to DCM 
                 Illegal DCM 
               
               
                   
                 Legal DCM 
               
               
                   
                 All DCMs 
               
               
                   
                 Maximum random number 
               
               
                   
                 [x] = delay unit. Delay time = (random number * 
               
               
                   
                 payload[x]) (ms) 
               
               
                  DCM TO SCM 
                 Pointer to RespondList 
               
               
                 Set the DCM to accept current SCM ID 
                   
               
               
                  SCM to DCM 
                 SCM ID 
               
               
                  DCM TO SCM 
                 Acknowledge or Failure Code 
               
               
                   
                 Pointer to RespondList 
               
               
                 Set the DCM to delete SCM ID accepted 
                   
               
               
                  SCM to DCM 
                 SCM ID 
               
               
                  DCM TO SCM 
                 Acknowledge or Failure Code 
               
               
                   
                 Pointer to RespondList 
               
               
                 Get the SCM ID accepted by the DCM 
                   
               
               
                  SCM to DCM 
                 REQUEST_SCM_ID 
               
               
                   
                 Pointer to RespondList 
               
               
                  DCM TO SCM 
                 SCM ID 
               
               
                   
               
            
           
         
       
     
     Table 35 lists illustrative operation-related communications between segment control module  524  and device control module  516 . 
     
       
         
           
               
             
               
                 TABLE 35 
               
             
            
               
                   
               
               
                 Illustrative operation-related communications between segment 
               
               
                 control module 524 and device control module 516. 
               
               
                 OPERATION 
               
            
           
           
               
               
            
               
                 Instruction(s) 
                 Argument(s) 
               
               
                   
               
               
                 Get product info 
                   
               
               
                  SCM to DCM 
                 GET_PRODUCT_INFOPointer to RespondList 
               
               
                  DCM TO SCM 
                 Data structure containing information on the fixture 
               
               
                   
                 for which the DCM is housedYYYYMMDD (BCD) 
               
               
                   
                 YY 
               
               
                   
                 YY 
               
               
                   
                 MM 
               
               
                   
                 DD 
               
               
                   
                 Pointer to FactoryList 
               
               
                   
                 Model number (ASCII) 
               
               
                   
                 Model number of led driver (ASCII) 
               
               
                   
                 Rated current output level ID (mA) 
               
               
                   
                 Percentage of customize current level (0.01%) 
               
               
                   
                 Schematic version (ASCII), PCB version (ASCII) 
               
               
                   
                 DeviceID 
               
               
                   
                 Firmware version (BCD) 
               
               
                   
                 Major 
               
               
                   
                 Bus protocol (BCD) 
               
               
                   
                 Major 
               
               
                   
                 Minor 
               
               
                   
                 Device type (Pointer to tab DeviceCategory) 
               
               
                   
                 Initial status level (0.01%) 
               
               
                 Set product info 
                   
               
               
                  Manufacturing to DCM 
                 Data structure containing fixture 
               
               
                   
                 parametersYYYYMMDD (BCD) 
               
               
                   
                 Pointer to FactoryList 
               
               
                   
                 Model number (ASCII) 
               
               
                   
                 Model number of led driver (ASCII) 
               
               
                   
                 Rated current output Level ID (mA) 
               
               
                   
                 Percentage of customize current Level (0.01%) 
               
               
                   
                 Schematic version (ASCII), PCB version (ASCII) 
               
               
                   
                 DeviceID 
               
               
                   
                 Initial status level (0.01%) 
               
               
                  DCM to specialized tool 
                 Acknowledge or Failure Code 
               
               
                   
                 Pointer to RespondList 
               
               
                 Get current state of DCM 
                   
               
               
                  SCM to DCM 
                 Get_Product_State 
               
               
                   
                 Pointer to RespondList 
               
               
                  DCM (lighting fixture) to SCM 
                 Data structure containing information on fixture 
               
               
                   
                 state. Including: 
               
               
                   
                 On/Off, 0 = off, 1 = On 
               
               
                   
                 Dimming curve mode, 0 = linear. 1 = logarithm 
               
               
                   
                 Product lifetime (hour) 
               
               
                   
                 Soft on fade rate 
               
               
                   
                 Fade to black rate 
               
               
                   
                 Initial status level (0.01%) (power on) 
               
               
                   
                 Color temperature mix level, (0.01%) 
               
               
                   
                 luminance level, (0.01%) 
               
               
                   
                 Channel number 
               
               
                   
                 Channel index (Pointer to tab SetParameterTable) 
               
               
                   
                 Channel dimming level (0.01%) . . . 
               
               
                   
                 Channel index (Pointer to tab SetParameterTable) 
               
               
                   
                 Channel dimming level (0.01%) 
               
               
                  DCM (motorize track head) to SCM 
                 Data structure containing information on fixture 
               
               
                   
                 state. Including:Pointer to RespondList 
               
               
                   
                 On/Off, 0 = off, 1 = on 
               
               
                   
                 Dimming curve mode, 0 = linear. 1 = logarithm 
               
               
                   
                 Product lifetime (hour) 
               
               
                   
                 Soft on fade rate 
               
               
                   
                 Fade to black rate 
               
               
                   
                 Initial status level (0.01%) 
               
               
                   
                 Color temperature mix level, (0.01%) 
               
               
                   
                 Luminance level, (0.01%) 
               
               
                   
                 Up/down position 
               
               
                   
                 Left/right position 
               
               
                   
                 Lens position 
               
               
                   
                 Channel number 
               
               
                   
                 Channel index (Pointer to tab SetParameterTable) 
               
               
                   
                 Channel index (Pointer to tab SetParameterTable) 
               
               
                   
                 Channel dimming level (0.01%) 
               
               
                 Set the parameter to DCM and DCM 
                   
               
               
                 return state info 
                   
               
               
                  SCM to DCM (lighting fixture) 
                   
               
               
                  SCM to DCM (motion sensor) 
                   
               
               
                  SCM to DCM (daylight sensor) 
                   
               
               
                  SCM to DCM (motorize track head) 
                   
               
               
                  DCM TO SCM 
                 Pointer to RespondList 
               
               
                 Get product lifetime from DCM 
                   
               
               
                  SCM to DCM 
                   
               
               
                  DCM TO SCM 
                   
               
               
                   
                 Pointer to RespondList 
               
               
                   
                 Product lifetime (hour) 
               
               
                   
               
            
           
         
       
     
     Table 36 lists illustrative group-related communications between segment control module  524  and device control module  516 . 
     
       
         
           
               
             
               
                 TABLE 36 
               
             
            
               
                   
               
               
                 Illustrative group-related communications between segment 
               
               
                 control module 524 and device control module 516. 
               
               
                 GROUP 
               
            
           
           
               
               
            
               
                 Instruction(s) 
                 Argument(s) 
               
               
                   
               
               
                 Set specific DCMs to join specific group 
                   
               
               
                  SCM to DCM 
                 Group number 
               
               
                   
                 Device1 ID 
               
               
                   
                 Device2 ID... 
               
               
                 Set specific DCMs to quit from specific group 
                   
               
               
                  SCM to DCM 
                 Group number 
               
               
                   
                 Device1 ID 
               
               
                   
                 Device2 ID... 
               
               
                 Delete specific group number from specific DCM 
                   
               
               
                  SCM to DCM 
                 Number of group, 999 = delete all groups 
               
               
                   
                 Group number one by one 
               
               
                  DCM TO SCM 
                 Acknowledge or Failure Code 
               
               
                   
                 Pointer to RespondList 
               
               
                 Get group number from the DCM 
                   
               
               
                  SCM to DCM 
                 GET_GROUP_MEMBERSHIP 
               
               
                   
                 Pointer to RespondList 
               
               
                  DCM TO SCM 
                 Number of group 
               
               
                   
                 Group number one by one 
               
               
                   
               
            
           
         
       
     
     Table 37 lists illustrative broadcast-related communications between segment control module  524  and device control module  516 . 
     
       
         
           
               
             
               
                 TABLE 37 
               
             
            
               
                   
               
               
                 Illustrative broadcast-related communications between segment 
               
               
                 control module 524 and device control module 516. 
               
               
                 BROADCAST 
               
            
           
           
               
               
            
               
                 Instruction(s) 
                 Argument(s) 
               
               
                   
               
               
                 Broadcast operation 
                   
               
               
                  SCM to DCM 
                 Group number, 0 = all device operation, other 
               
               
                   
                 value is corresponding group number 
               
               
                   
                 Pointer to tab SetParameterTable 
               
               
                   
               
            
           
         
       
     
     Table 38 lists illustrative update-related communications between segment control module  524  and device control module  516 . 
     
       
         
           
               
             
               
                 TABLE 38 
               
             
            
               
                   
               
               
                 Illustrative update-related communications between segment 
               
               
                 control module 524 and device control module 516. 
               
               
                 UPDATE 
               
            
           
           
               
               
            
               
                 Instruction(s) 
                 Argument(s) 
               
               
                   
               
               
                 Set DCM is ready to update firmware 
                   
               
               
                  SCM to DCM 
                 START_Pointer to RespondList 
               
               
                   
                 FIRMWARE_UPDATE 
               
               
                  DCM TO SCM 
                   
               
               
                 Set updated packet info to DCM 
                   
               
               
                  SCM to DCM 
                 Length of data content in bin file 
               
               
                  DCM TO SCM 
                 Acknowledge or Failure Code 
               
               
                   
                 Pointer to RespondList 
               
               
                 Set specific packet to DCM 
                   
               
               
                  SCM to DCM 
                 Specific packet number 
               
               
                   
                 Corresponding content 
               
               
                  DCM TO SCM 
                 Acknowledge or Failure Code 
               
               
                   
                 Pointer to RespondList 
               
               
                 Set DCM to end update 
                   
               
               
                  SCM to DCM 
                 Pointer to RespondList 
               
               
                   
                 END_FIRMWARE_UPDATE 
               
               
                  DCM TO SCM 
               
               
                   
               
            
           
         
       
     
       FIG.  6    shows illustrative cartridge  600 . Cartridge  600  is seated in socket  602  in interface  526  (shown in  FIG.  5   ). Cartridge  600  includes receptacle  604  for receiving an input  506 . Cartridge  600  may include terminals  606  for communicating electronically with interface  526  of fixture controller  520 . Receptacles  604  may be configured to match a standard commercially available connector corresponding to one of inputs  506 . 
       FIG.  7    shows illustrative cartridge  700 . Cartridge  700  is seated in socket  602  in interface  526  (shown in  FIG.  5   ). Cartridge  700  includes receptacle  704  for receiving an input  506  of fixture controller  520 . Cartridge  700  includes terminals  606  for communicating electronically with interface  526 . Receptacles  704  may be configured to match a standard commercially available connector corresponding to one of inputs  506 . 
     Receptacle  704  may be configured such that it cannot receive a connector that may be received by receptacle  604 . Receptacle  604  may be configured such that it cannot receive a connector that may be received by receptacle  704 . 
       FIG.  8    shows illustrative fixture support  800 . Fixture support  800  may have one or more features in common with fixture support  310  (shown in  FIG.  3   ). Fixture support  800  may include spine  802 . Fixture support may include panel  804 . Fixture support may include panel  806 . Spine  802 , panel  804  and panel  806  may define fixture docking area  808 . Spine  802 , panel  804  and panel  806  may define connector slot  810 . Panel  804  and panel  806  may define fixture slot  812 . Fixtures such as  316  (shown in  FIG.  3   ) may be docked in docking area  808 . Fixtures such as  318  (shown in  FIG.  3   ) may be mounted in fixture slot  812 . Fixture docking tier  814  may be disposed between panel  804  and  806 . 
       FIG.  9    is a view of fixture support  800  that is different from that shown in  FIG.  8   .  FIG.  9    shows that spine  802  may include bridge  902 . Bridge  902  may span between panel  804  and panel  806 . Fixture docking tier  814  may extend longitudinally to the left along longitudinal direction L (left). End  904  of tier  814  may be flush with end  906  of fixture support  800 . Tier  814  may include platform  908 . Tier  814  may include connection field  912 . Bridge  902  may include abutment  910 . Abutment  910  may be set back to the right along direction L (right) from end  904 . The directions L (left) and R (right) are for description of relative positions within fixture support  800 , and do not necessarily define an orientation of fixture support  800  relative to any other frame of reference. 
       FIG.  10    shows that platform  908  may be disposed above, in direction V (up), from connection field  912 . The directions V (up) and V (down) are for description of relative positions within fixture support  800 , and do not necessarily define an orientation of fixture support  800  relative to any other frame of reference. Platform  908  may include abutment  1002  between platform  908  and connection field  912 . 
     Tier  814  may include back-plate  1004 . Back-plate  1004  may extend above, and define a right limit of, connection field  912 . Connection field  912  may provide access, from above tier  814 , to conductors in tier  814 . A connector bridging from another fixture support to fixture support  800  may thus be made without interfering with fixture docking area  808  below tier  814 . 
     Docking tier  814  may include conductor  1006 . Docking tier  814  may include conductor  1008 . Docking tier  814  may include conductor  1010 . Docking tier  814  may include conductor  1012 . A pair of the conductors, one positive and one negative, may be a communication bus that may transmit communications  410  (shown in  FIG.  4   ). A pair of the conductors, one positive and one negative, may be a power rail that may transmit power from transformer  546  (shown in  FIG.  5   ). Docking tier  814  may include magnetic strip  1014 . Back-plate  1004  may include ribs such  1016 . Back-plate  1004  may include grooves  1018 ,  1020 ,  1022  and  1024 . Together with bridge  902 , grooves  1018 ,  1020 ,  1022  and  1024  may form slots  1026 ,  1028 ,  1030  and  1032 . 
     Panel  804  may include groove  1034 . Panel  806  may include groove  1036 . The grooves may engage with a complementary feature on a fixture such as  316  (shown in  FIG.  3   ). Panel  804  may include ridge  1038 . Panel  806  may include ridge  1040 . The ridges may engage with a complementary feature on the fixture. 
     Docking tier  814  may be disposed in slot  1028 . 
     Fixture support  800  may include slot  1041 . Slot  1041  may be above tier  814 . Slot  1041  may receive a fixture support connector. 
     Fixture support  800  may include slot  1042 . Slot  1042  may be above slot  1041 . Slot  1042  may include grooves  1044  and  1046 . Slot  1042  may receive a fixture such as fixture  318  (shown in  FIG.  3   ). 
     Fixture support  800  may include overhangs  1048  and  1050 . 
     Fixture support  800  may define U-channel  1052 . U-channel  1052  may be defined by docking tier  814 , panel  804  and panel  806 . Panel  804  may include distal edge  1054 . Panel  806  may include distal edge  1056 . The fixture may be retractable within U-channel  1052 . A lowest extreme of the fixture may be retracted above distal edge  1054 . A lowest extreme of the fixture may be retracted above distal edge  1056 . The lowest extreme may be a lip. 
     Fixture support  814  may have docking area width  1058 . 
       FIG.  11    shows that conductors  1006 ,  1008 ,  1010  and  1012  may be disposed in grooves  1128 ,  1130 ,  1132  and  1134 , respectively. Tier  814  may include lips  1144 ,  1146 ,  1148  and  1150 , corresponding to grooves  1128 ,  1130 ,  1132  and  1134 . The lips may retain the conductors in tier  814 . Tier  814  may include tapers  1153 ,  1155 ,  1157  and  1159 , corresponding to grooves  1128 ,  1130 ,  1132  and  1134 . A taper may guide a terminal from a fixture such as  316  toward a conductor. A taper may guide a terminal from a fixture such as  316  into electrical communication with a conductor. A taper may guide a terminal from a fixture such as  316  into direct contact with a conductor. Gaps  1152 ,  1154 ,  1156 , and  1158  may provide access for direct contact between the fixture and a conductor. 
     Magnetic strip  1014  may be disposed in groove such as  1160 . Tier  814  may include lip  1162  for retaining magnetic strip  1014 . Gap  1164  may expose magnetic strip  1014 . Gap  1164  may have a magnetic permeability that is less than that of body  1168  of tier  814 . Gap  1164  may be a gap that includes no solid material. 
       FIG.  12    shows that docking area  808  (shown in  FIG.  8   ) may have width  1100 . Width  100  may be commensurate with docking area width  1058 . Docking area  808  may have left end  1102 . Left end  1102  may be coincident with end  906 . Docking area  808  may have a counterpart end on an opposite end (not shown) of fixture support  800 . One or more of conductors  1006 ,  1008 ,  1010  and  1012 , grooves  1128 ,  1130 ,  1132  and  1134 , tapers  1153 ,  1155 ,  1157  and  1159 , gaps  1152 ,  1154 ,  1156 , and  1158 , groove  1160  and gap  1164  may extend between left end  1102  and the opposite right end of fixture support  800 . 
       FIG.  13    shows that support  800  may include wall  1302 . Wall  1302 , a facing, opposite wall (not shown) on panel  804 , and abutment  910  may form bay  1304  in which a connector may be lodged. Rail  1306  may be mated with a corresponding groove on the connector. Another rail (not shown) on panel  804  may be mated with another corresponding groove on the connector. The panels and rails may secure the connector against rotation about a longitudinal axis in directions L. The panels and rails may secure the connector against rotation about a vertical axis in directions V. 
     Abutment  1002 , field  912  and back-plate  1004  may form recess  1308  in which the connector can make electrical contact with conductors. Abutment  1002  may be oriented at an angle with respect to field  912 . The angle may be sufficiently steep to retain the connector. The angle may be sufficiently shallow to allow the connector to be withdrawn by a user by hand by overcoming resistance of the slope. 
     Fixture support  800  may include hole  1310 . Hole  1310  may provide clearance for a fastener. The fastener may be threaded for engagement with the connector after the connector is inserted in fixture support  800 . 
       FIG.  14   . shows illustrative connector  1400 . Connector  1400  may include base  1402 . Connector  1400  may include cap  1404 . Connector  1400  may include cover  1406 . Connector  1400  may include port  1408 . Connector  1400  may include port  1410 . Connector  1400  may include contact  1412 . Connector  1400  may include contact  1414 . Contact  1412  may be in electrical communication with contact  1414 . A contact may include a sprung terminal. 
     Cover  1406  may include foot  1416 . Cover  1406  may include foot  1418 . 
     Contact  1412  may be biased to extend through a slot (not shown) in foot  1416 . Contact  1414  may be biased to extend through a slot (not shown) in foot  1418 . 
     Brace  1420  may encompass a first region of connector  1400 . Brace  1422  may encompass a second region of connector  1400 . Brace  1422  may have one or more features in common with brace  1420 . 
     Brace  1424  may be inserted into slot  1041  to lodge brace  1424  in fixture support  800 . Foot  1418  may be disposed in recess  1308 . Contact  1414  may be urged downward into contact with a conductor in field  912 . 
     Brace  1422  may provide to, or receive from, brace  1420  electrical continuity. Brace  1422  may provide to, or receive from, brace  1420  mechanical stability. When brace  1422  and brace  1422  are lodged in ends of different fixture supports, the fixture supports may be abutted without encroaching upon the fixture docking area of either fixture support. 
       FIG.  15    shows brace  1422  lodged in fixture support  800  (shown in partial cross-section). Screw  1502  may fasten brace  1422  to fixture  800 . 
       FIG.  16    shows connector  1400 . 
       FIG.  16    shows that connector  1400  may include contacts  1602 ,  1606  and  1610 , which may be in electrical communication, respectively, with contacts  1604 ,  1608  and  1612 . Contacts  1414 ,  1604 ,  1608  and  1612  may be aligned, respectively, with conductors  1006 ,  1008 ,  1010  and  1012 . Contacts  1412 ,  1602 ,  1606  and  1610  may be aligned with conductors disposed in a different fixture connector and corresponding to conductors  1006 ,  1008 ,  1010  and  1012  to provide electrical communication between conductors  1006 ,  1008 ,  1010  and  1012  and the corresponding conductors. 
     Grooves  1614  and  1616  may engage, respectively, rail  1306  and the complementary rail in fixture support  800 . Grooves  1618  and  1620  may engage, respectively, in a different fixture support, a rail corresponding to rail  1306  and a rail corresponding to the complementary rail in fixture support  800 . 
       FIG.  17    shows that ports  1408  and  1410  may include terminals. Each one of the terminals in port  1408  may be in electrical communication with a corresponding one of contacts  1412 ,  1602 ,  1606  and  1610 . Each one of the terminals in port  1410  may be in electrical communication with a corresponding one of contacts  1414 ,  1604 ,  1608  and  1612 . 
       FIG.  18    shows base  1402  with cover  1406  removed. Base  1402  may include plate  1800 . Plate  1800  may include conductors for providing electrical communication between the contacts and corresponding terminals in ports  1408  and  1410 . Contacts  1412  and  1414  may be connected by cross-piece  1802 . Contact  1412  may be suspended from plate  1800  by spring  1804 . Contact  1414  may be suspended from plate  1800  by spring  1806 . The other contacts may be connected by corresponding cross-pieces. The other contacts may be suspended by corresponding springs. 
     The springs may allow the contacts to retract in response to contact with platform  908  upon insertion of connector  1400  into fixture support  800 . The springs may retain the contacts in contact with the connectors when head is in recess  1308 . 
       FIG.  19    shows contacts and springs in brace  1422 . Plate  1800  may include conductors  1902 ,  1904 ,  1906  and  1908 . Conductors  1902 ,  1904 ,  1906  and  1908  may provide electrical communication between springs  1806 ,  1908 ,  1910  and  1912 , respectively, and corresponding terminals in port  1410 . Contacts  1414 ,  1604 ,  1608  and  1612  may include tabs such as tab  1914 . Springs  1806 ,  1908 ,  1910  and  1912  may be in electrical communication with corresponding tabs. Contacts  1414 ,  1604 ,  1608  and  1612  may thus change position relative to plate  1800  and maintain electrical communication with conductors  1902 ,  1904 ,  1906  and  1908 , and the corresponding contacts of brace  1420 . 
     Brace  1420  may include an arrangement analogous to that of brace  1424 . 
       FIG.  20    shows illustrative connector  2000 . Connector  2000  may include brace  2002 . Brace  2002  may have one or more features in common with brace  1422  (shown in  FIG.  14   ). Connector  2000  may include bundle  2004  of conductors. Connector  2000  may include wall  2006 . 
     Bundle  2004  may include power conductors. Bundle  2004  may include power conductors for power transmission. Bundle  2004  may include communication conductors for communications such as  410 . Bundle  2004  may be included in a cable such as cable  317 . 
     Wall  2006  may include an electrically non-conductive plate. When brace  2002  is lodged in a fixture support such as  800 , wall  2006  may abut or nearly abut an end of the fixture support, such as end  906 . Wall  2006  may be disposed in abutment or near abutment with, and perpendicular to, docking tier  814 . 
     Brace  2002  may include port  2008 . Brace  2002  may include cover  2010 . 
     Fitting  2012  may mechanically fix bundle  2004  to brace  2002 . 
       FIG.  21    shows illustrative brace  2002  from view lines  21 - 21  (show in  FIG.  20   ), with wall  2006  and cover  2010  removed. Power conductors  2102  and  2104  may provide power to cross-pieces  2106  and  2108 , respectively. Communication conductors  2110  and  2112  may provide communications to cross-pieces  2114  and  2116 , respectively. Power conductors  2102  and  2104  may be electrically isolated from cross-pieces  2114  and  2116 . Communication conductors  2110  and  2112  may be electrically isolated from cross-pieces  2106  and  2108 . 
     Cross-piece ends  2118 ,  2120 ,  2122  and  2124  may be anchored to plate  2126 . Cross-piece ends  2118 ,  2120 ,  2122  and  2124  may be free ends. 
       FIG.  22    shows illustrative hub arrangement  2200 . Hub arrangement  2200  may include junction  2202 . Hub arrangement  2200  may include brace  2204 . Brace  2204  may have one or more features in common with brace  1422  (shown in  FIG.  14   ). Hub arrangement  2200  may include bracket  2206 . Bracket  2206  may be seated in annular receptacle  2208  between spacer  2210 , lower unit  2212  and upper unit  2213 . Bracket  2206  may be slidable circumferentially in directions C about spacer  2210 . 
     Brace  2204  may mechanically and electrically engage with a fixture support such as  800  (shown in  FIG.  8   ). 
     Bracket  2206  may include power and communication conductors (not shown) that are in electrical communication with contacts of brace  2204 . The bracket  2206  power and communication conductors (not shown) may be in electrical communication with corresponding power and communication conductors (not shown) of junction  2202 . 
     Bracket  2206  may include switch  2214 . Switch  2214  may include knob  2215 . Switch  2214  may close to provide electrical communication between the bracket  2206  conductors and the junction  2202  conductors. Switch  2214  may open to interrupt electrical communication between the bracket  2206  conductors and the junction  2202  conductors. In an arrangement in which junction  2202  provides power to the fixture support, switch  2214  may be used to set whether the fixtures of the fixture support have access to power. In an arrangement in which junction  2202  provides communication to the fixture support, switch  2214  may be used to set whether the fixtures of the fixture support have access to communication. 
     Bracket  2206  may include carriage  2216 . Carriage  2216  may support bracket  2206  at a fixed radial distance from centerline L of junction  2202 . Carriage  2216  may support bracket  2206  at a fixed vertical position relative to junction  2202 . 
     Pegs  2218  together may form lower fence  2220 . Pegs  2218  may include screws, bolts, threaded rod, or the like. Lower fence  2220  may guide carriage  2216  as carriage  2216  is moved about spacer  2210 . Upper unit  2213  may include upper fence (not shown). The upper fence and lower fence  2220  may keep support bracket  2206  at a fixed radial distance from centerline L of junction  2202 . The upper fence and lower fence  2220  may support bracket  2206  at a fixed vertical position relative to junction  2202 . 
     Bracket  2206  may include surface  2222  that may conform to outer surface  2224  of upper unit  2213 . Bracket  2206  may include surface  2226  that may conform to outer surface  2228  of lower unit  2212 . Outer surface  2226  may be an extension of outer surface  2224 . 
     Carriage  2216  may include surface  2228  that may conform to outer surface  2230  of spacer  2210 . 
       FIG.  23    shows surfaces  2222 ,  2226  and  2228  and groove  2221 . Carriage  2216  may include carriage extension  2302 . Carriage extension  2302  may be inserted into the upper fence of upper unit  2213 . 
       FIG.  24    shows pins  2400  extending through top  2402  of carriage  2216 . Carriage  2216  may include a pin  2400  (three of four shown) corresponding to, and in electrical communication with, each of the contacts in brace  2204 . Carriage extension  2302  may have surface  2404 . Surface  2404  may interact with the upper fence to retain carriage  2216  in its operational position in receptacle  2208 . 
       FIG.  25    shows arrangement  2500  for providing electrical continuity through brace  2204 , bracket  2206  and carriage  2216 , which are partially shown, to upper unit  2213  loop conductors  2515  of junction  2202 . Contact  2502  may be a communication signal contact. Contact  2504  may be a power contact. Cross-piece  2506  may run from contact  2502  to terminal  2508 . Zig-zag spring  2507  may support cross-piece below plate  2509  of brace  2204 . 
     Switch  2214  may include slide  2513 . Switch  2214  may include material  2517 . Material  2517  may include material that is not electrically conductive to DC current. Material  2517  may include material that is not electrically conductive to AC current. Material  2517  may include material that has dielectric properties. Switch  2214  may include material  2519 . Material  2519  may include material that is electrically conductive to DC current. Material  2517  may include material that is electrically conductive to AC current. Material  2519  may be arranged in slide  2513  as feedthroughs, such as  2509 . 
     Terminal  2508  may be switched into electrical communication with terminal  2510  via feedthrough  2511 . 
     Slide  2513  may be moved up to bring into electrical communication terminal  2508 , terminal  2510  and feedthrough  2511 . Terminal  2508  may be switched out of electrical communication with terminal  2510  by sliding slide  2513  to take feedthrough  2511  out of electrical communication with terminal  2508  and terminal  2510 . 
     Slide  2513  may be fixed to knob  2215 . A user may slide slide  2513  up or down by moving knob  2215  up or down, respectively. Terminals  2508  and  2510  may be urged toward each other by springs  2512  and  2514 , respectively. Panels  2516  and  2518  may provide reactive forces to springs  2512  and  2514 , respectively. 
     The other contacts of brace  2204  may be analogously in electrical communication with pins  2524 ,  2526  and  2528 . The pins may be sprung to urge them into contact with the loop conductors. Power conducting pins  2524  and  2526  may have diameters greater than those of communication pins  2522  and  2528 . 
       FIG.  26    shows illustrative bracket chassis  2602 . Chassis  2602  may be monolithic with cover  2010 . Chassis  2602  may be fixed to bracket  2206 . Chassis  2602  may include slot  2604 . Slot  2604  may guide the sliding of slide  2513  (shown in an OFF position). Chassis  2602  may support structure  2606 . Structure  2606  may include a ledge such as ledge  2608 . Structure  2606  may include a facet such as facet  2610 . Terminal  2520  may include upper prong  2612 . Terminal  2520  may include lower prong  2614 . Facet  2610  may interfere with upward motion of upper prong  2612 . Ledge  2608  may interfere with downward motion of lower prong  2614 . Chassis  2602  and structure  2606  may thus retain terminal  2510  in a vertical position or range when slide  2513  is moved up or down. 
       FIG.  27    shows bracket chassis  2602  from a perspective different from that shown in  FIG.  26   . Chassis  2602  may support structure  2706 . Structure  2706  may include a ledge such as ledge  2708 . Structure  2706  may include a facet such as facet  2710 . Facet  2710  may interfere with upward motion of terminal  2508 . Ledge  2708  may interfere with downward motion of terminal  2508 . Chassis  2602  and structure  2706  may thus retain terminal  2508  in a vertical position or range when slide  2513  is moved up or down. 
     Feedthroughs  2511 ,  2702 ,  2704  and  2705  are positioned away from, and not in electrical communication with, corresponding terminals such as  2508  and  2520 . Knob  2215  is in the OFF position. Slide  2513  is in a lowered position. 
       FIG.  28    shows bracket chassis  2602  with slide  2513  in a raised position in slot  2604  (occluded). Knob  2215  is in the ON position. Feedthroughs  2511 ,  2702  (occluded),  2704  (occluded) and  2705  (occluded) are positioned in line with, and in electrical communication with, corresponding terminals such as  2508  and  2520 . 
       FIG.  29    shows brace  2204  in part. Zig-zag spring  2507  may provide resilient mechanical support to cross-piece  2506  from plate  2509 . Zig-zag spring  2507  may provide electrical communication between contact  2502  and conductor  2902  in plate  2509 . Spring  2904  may provide resilient mechanical support to contact  2502  from plate  2509 . Spring  2904  may provide electrical communication between contact  2502  and conductor  2902  in plate  2509 . 
       FIG.  30    shows bracket  2206  mechanically and electrically engaged with junction  2202 . Upper unit  2213  may include disc  3002 . Disc  3002  may include loop conductors  2515 . Loop conductors  2515  may include conductors  3004 ,  3006 ,  3008  and  3010 . Conductors  3004 ,  3006 ,  3008  and  3010  may be in electrical communication with contacts  2502 ,  2504 ,  3012  and  3014 . 
     Upper unit  2213  may include upper fence  3016 . Upper fence  3016  may receive carriage extension  2302 . Upper fence  3016  may include surface  3018  for retaining carriage extension  2302  against motion in a direction radially away from the central axis of junction  2202 . 
     Lower unit  2212  may include bottom  3020 . 
       FIG.  31    shows brace  2204 , bracket  2206 , carriage  2216  and junction  2202 , with bottom  3020  removed. Heads such as  3102  of lower fence  2220  pegs  2218  may be accessed through plate  3104 . Heads  3102  may be turned to raise and lower pegs  2218 . Pegs  2218  may include a threaded section (not shown) that may be threadingly engaged with lower unit  2212 . Pegs  2218  may be sprung to bias pegs  2218  toward carriage  2216 . Detents (not shown) may retain pegs  2218 , if sprung, to retain the pegs in a state in which the peg springs are compressed. Plate  3104  may include indicants such as  3108  to indicate degrees of arc about the central axis of junction  2202 . A bracket such as  2206  may be moved continuously about the central axis and set at an arc angle chosen by the user. 
     Fasteners such as  3106  may hold plate  3104  to lower unit  2212 . Fasteners such as  3110  may pass through spacer  2210  into upper unit  2213 . Fasteners  3110  may fasten upper unit  2213 , spacer  2210  and lower unit  2212 . 
     The user may install carriage  2216  in junction  2202 . Bottom  3020  may be removed from junction  2202 . A selection of heads  3102  may be turned to lower corresponding pegs  2218 . Carriage  2216  may be inserted into receptacle  2208 . The selection of heads  3102  may be turned to raise corresponding pegs  2218 . Pegs  2218  may be tightened to make snug the engagement of carriage extension  2302  with upper fence  3016 . Pegs  2218  may be tightened to position one or more of: carriage extension  2302  relative to upper fence  3016 ; lower fence  2220  relative to groove  2221 ; bracket  2206  surface  2222  relative to outer surface  2224  of upper unit  2213 ; bracket  2206  surface  2226  relative to outer surface  2228  of lower unit  2212 ; and carriage  2216  surface  2228  relative to outer surface  2228  of spacer  2210 ; pins  2400  relative to conductors  3004 ,  3006 ,  3008  and  3010 . 
     The user may remove carriage  2216  from junction  2202  by turning a selection of heads  3102  to lower corresponding pegs  2218 . The user may then remove carriage  2216  from receptacle  2208 . 
       FIG.  32    shows arrangement  3200 . Arrangement  3200  may include junction  2202 , brace  2204  and bracket  2206 . Arrangement  3200  may include five other braces that may have one or more features in common with brace  2204 . Arrangement  3200  may include five other brackets that may have one or more features in common with bracket  2206 . 
     Each of the other braces may have a contact in electrical communication, through junction  2202 , with contact  2502 . Each of the other braces may have a contact in electrical communication, through junction  2202 , with contact  2504 . Each of the other braces may have a contact in electrical communication, through junction  2202 , with contact  3012 . Each of the other braces may have a contact in electrical communication, through junction  2202 , with contact  3014 . Each of the brackets may have a switch that may interrupt electrical communication between the contacts that are configured to transmit power. 
       FIGS.  33 - 38    show illustrative fixture support joint  3301  and illustrative switch assembly  3403 . 
     Fixture support joint  3301  may include an intersection of two or more fixture supports such as fixture support  800 . The fixture supports may be adapted to connect with each other. Illustrative switch assembly  3403  may provide electrical power distribution among the fixture supports. Illustrative switch assembly  3403  may provide electrical communication signal distribution among the fixture supports. 
     Fixture support joint  3301  may include strip  3302 . Strip  3302  may include a polymer body. Strip  3302  may include conductors. The polymer body may include electrically conductive polymer. Strip  3302  may be mounted on the fixture support joint  3301 . Strip  3302  may have one or more features in common with docking tier  814 , and may provide one or more of the functions of docking tier  814  and the conductors, magnet strip, and other elements associated therewith. Switch assembly  3403  may include a mounting plate  3504 . Switch assembly  3403  may include conductive module  3505 . Conductive module  3505  may have one or features in common with brace  1420 . Conductive module  3505  may be mounted on mounting plate  3504  in a movable manner. Adjusting member  3406  may be configured to adjust a position of conductive module  3505 . Adjusting member  3406  may move conductive module  3505  closer to or away from strip  3302 . Mounting plate  3504  may be fixed to fixture support joint  3301 . 
     When conductive module  3505  is made to move close to and abut against strip  3302 , two fixture supports may be brought into electrical communication. When conductive module  3505  is made to move away from strip  3302 , the electrical communication of the two fixture supports may be interrupted. 
     When fixture support joint  3301  is a one-way structure, one conductive module  3505  and one adjusting member  3406  may be provided. When fixture support joint  3301  is a two-, three- or four-way structure, two, three or four corresponding conductive modules  3505 , and two, three, or four corresponding adjusting members  3406  may be provided. When fixture support joint  3301  is an n-way structure, n corresponding conductive modules and n corresponding adjusting members  3406  may be provided. n may be any suitable number. 
     Conductive module  3505  may include lifting seat  3607 . Conductive module  3505  may include base  3608 . Base  3608  may be disposed at the bottom of lifting seat  3607 . Conductive module  3505  may include several conductive sheets  3609 . Conductive sheets  3609  may be disposed in base  3608 . The bottom of base  3608  may be provided with several openings  3610 , an end of one of conductive sheets  3609  to extend therefrom. The bottom of mounting plate  3504  may be provided with several guide posts  3711 . Lifting seat  3607  may be provided with guide holes  3712  for cooperative insertion of guide posts  3711 . Bottom ends of guide posts  3711  may be connected to limiting screws  3613 . Limiting screws  3613  limit lifting seat  3607  between mounting plate  3504  and limiting screws  3613 . A first spring  3714  may be sleeved on the outer circumference of guide posts  3711 . Two ends of first spring  3714  may be connected to mounting plate  3504  and lifting seat  3607 , respectively. 
     Adjusting member  3406  may be an adjusting bolt. Base  3608  may be provided with a through hole  3816 . Through hole  3816  may provide clearance for the adjusting bolt. Lifting seat  3607  may be provided with a first threaded hole  3617  for disposing the adjusting bolt. Mounting plate  3504  may be provided with a second threaded hole  3718 . Groove  3718  may be cooperatively screwed to the adjusting bolt. First threaded hole  3617  and second threaded hole  3718  may be arranged correspondingly. 
     Strip  3302  may be provided with an access hole (not marked in the drawing). Adjusting member  3406  may be accessed via the access hole. Guide post  3711  may be cooperative with guide hole  3712 , so that lifting seat  3607  of conductive module  3505  is stable when moving vertically. Limit screw  3613  and mounting plate  3504  may limit the moving range of lifting seat  3607 . Limit screw  3613  and mounting plate  3504  may thus define a moving range of conductive module  3505 . First spring  3714  may abut and move lifting seat  3607  to facilitate the downward movement and resetting of conductive module  3505 . When conductive module  3505  is close to strip  3302 , one end of a conductive sheet  3609  may extend out of opening  3610  to abut strip  3302  for electrical conduction. The adjusting bolt may be cooperatively connected to first thread groove  3617  and second thread groove  3718 . A head of the adjusting bolt may abut against lifting seat  3607 . Through hole  3816  and the access hole may be arranged correspondingly. The adjusting bolt may be exposed via through hole  3816  and the access hole. 
     Base  3608  may be provided with several accommodating slots  3819  for accommodating the several conductive sheets  3609 . The top of an inner wall of an accommodating slot  3819  may be connected to a second spring  3820 . Second spring  3820  may be connected to the top of conductive sheet  3609  to maintain one end of the conductive sheet  3609  in a state of extension out of opening  3610 . The two ends of second spring  3820  may be connected to the inner wall of the accommodating slot  3819  and conductive sheet  3609 , respectively, to ensure that one end of conductive sheet  3609  is maintained in a state of extension out of opening  3610 . One end of conductive sheet  3609  may be provided with a protrusion that extends out of opening  3610 . One end of conductive sheet  3609  may extend out of opening  3610  and abut against strip  3302  to provide electrical communication between conductive sheet  3609  and strip  3302 . 
     A top end of the adjusting bolt may protrude from second threaded hole  3718 . The top end may be connected to limiting post  3721 . The top end of second threaded hole  3718  may include conduction limit block  3422 . The top end of second threaded hole  3718  may include disconnection limit block  3423 . Conduction limit block  3422  and disconnection limit block  3423  may cooperatively abut limiting post  3721  for limiting motion of the adjusting bolt. When the adjusting bolt is rotated to move conductive module  3505  vertically, conductive sheets  3609  of the conductive module  3505  abuts strip  3302  for conduction or conductive sheets  3609  are moved away from strip  3302  for disconnection. Conduction limit block  3422  and disconnection limit block  3423  may cooperatively abut limiting post  3721 , and the rotation range of the adjusting bolt thus may be limited. 
     Conductive module  3505  may be mounted on mounting plate  3504  in a limited manner. Adjusting member  3406  may adjust vertically conductive module  3505 . Adjusting member  3406  may adjust the position of conductive module  3505  closer to, or farther away from, a conductor of strip  3302 . When conductive module  3505  is made to move close to and abut strip  3302  by operating the adjusting member  3406 , conduction may be effected. When conductive module  3505  is made to move away from strip  3302  by operating adjusting member  3406 , disconnection may be effected. 
       FIG.  39    shows arrangement  3200  with fixture support  800  attached to bracket  2206 . Connector  2000  is inserted in fixture support  800 . Other fixture supports having one or more features in common with fixture support  800  may be attached to corresponding other brackets. Power supplied through bundle  2004  may be transmitted from fixture support  800 , through junction  2202 , to the other fixture supports. Communications such as  410  transmitted through bundle  2004  may be transmitted from fixture support  800 , through junction  2202 , to the other fixture supports. 
       FIG.  40    shows illustrative fixture head  4000 . Fixture head  4000  may connect a fixture such as  316  to a fixture support such as  400 . Fixture head  4000  may include frame  4002 . Fixture head  4000  may include latch  4004 . Fixture head  4000  may include latch  4006 . Fixture head  4000  may include pick-up unit  4008 . Pick-up unit  4008  may include electrical contact pins  4010 . Contact pins  4010  may transfer power and communication signals between fixture head  4000  and docking tier  814 . Fixture head  4000  may include a magnetic element (not shown). Fixture head  4000  may include ferrous material. The magnetic element or the ferrous material may engage magnetically with magnetic strip  1014 . The magnetic engagement may secure fixture  316  to docking tier  814 . Contact pins  4010  may be sprung so that they retract into pick-up unit  4008  when fixture head  4000  is docked flush against docking tier  814 . 
     Pick-up unit  4008  may include pin pairs  4012 ,  4014 ,  4016  and  4018 . Pairs  4012 ,  4014 ,  4016  and  4018  may be positioned to contact, respectively, conductors  1006 ,  1008 ,  1010  and  1012  in docking tier  814 . 
     Latches  4004  and  4006  may include, respectively, detents such  4020  and  4022 . Detents  4020  and  4022  may be biased to extend outward from latches  4004  and  4006 . The detents in operation may be supported by ridges  1038  and  1040 . Ridges  1038  and  1040  may prevent the fixture from dropping from fixture support  800  if the magnetic engagement fails. Bezels such as  4024  may conform to angular limbs of ridges  1038  and  1040 . Fixture head  4000  may include actuators such as button  4026  to withdraw the detents. Latches  4004  and  4006  may each include releases (not shown) to withdraw the detents into the latches. Fixture head  4000  may include backwall  4030 . Back side  4032  of backwall  4030  may contact docking tier  814  when the fixture is disposed in fixture support  800 . Direction R is the rear direction. Direction F is the forward direction. When disposed in fixture support  800 , back side  4032  is forward of docking tier  814 . 
     The fixture may be secured to fixture head  4000  in a position forward of fixture head  4000 . The fixture may be secured to frame  4002 . 
     The fixture may be installed in fixture support  800  by inserting fixture head  4000  in U-channel  1052 . A user may insert fixture head  4000  along direction V(up) (shown in  FIG.  9   ) into U-channel  1052 . A user may slide fixture head  4000  along a direction perpendicular to direction V(up) (shown in  FIG.  9   ) into U-channel  1052 . 
       FIG.  41    shows illustrative chassis  4100  of latch  4006 . Latch  4006  may include detent  4102 . Latch  4006  may include release  4104 . Latch  4006  may include spring  4106 . Release  4104  may include retraction slot  4108 . Release  4104  may include retraction slot  4110 . Release  4104  may include engagement element  4112 . Engagement element  4112  may include a recess, a ridge, an edge, a surface, or any other suitable engagement element. Detent  4022  may include boss  4114 . Boss  4114  may be disposed in retraction slot  4108 . Detent  4102  may include boss  4116 . Boss  4116  may be disposed in retraction slot  4110 . 
     Detents such as  4020  and  4022  may deflect inward into latches such as  4006  when fixture head  4000  is inserted in direction V(up) into U-channel  1052 . The detents may spring out after passing ridges  1038  and  1040 . Ridges  1038  and  1040 , in an extended state, may prevent the fixture from coming out of U-channel  1052  in the V(down) direction. The detents, supported by ridges  1038  and  1040 , may retain fixture head  4000  in U-channel  1052  when a user inserts fixture head  4000  into U-channel  1052  in a direction perpendicular to V(up) or V(down). The detents, supported by ridges  1038  and  1040 , may retain fixture head  4000  in U-channel  1052  when a user slides fixture head  4000 , in a direction perpendicular to V(up) or V(down), from one position to another in U-channel  1052 . 
     Chassis  4100  may include course  4118 . Release  4104  may be constrained to move along course  4118 . Chassis  4100  may include course  4120 . Detent  4022  may be constrained to move along course  4120 . Chassis  4100  may include course  4122 . Detent  4102  may be constrained to move along course  4122 . 
     Chassis  4100  may include front side  4124  of backwall  4030 . Chassis  4100  may include side wall  4126 . Side wall  4126  may form a perimeter around release  4104 . 
     Spring  4106  may bias release  4104  toward section  4128  of side wall  4126 . Retraction slots  4108  and  4110  may be oriented such that when spring  4106  extends, retraction slots  4108  and  4110  act on bosses  4114  and  4116  to project detents  4022  and  4102  outwardly away from side wall  4126 . The force of spring  4106  may hold detents  4022  and  4102  outwardly away from side wall  4126  in a projected configuration. 
     The user may move release  4104  toward section  4130  of side wall  4126  against spring  4106 . Latch  4006  may include block  4127 . Block  4127  may support release  4104  against movement to the rear of chassis  4100 . The motion of release  4104  toward section  4130  may cause retraction slots  4108  and  4110  to act on bosses  4114  and  4116  to withdraw detents  4022  and  4102  inwardly. The detents may be drawn inward or flush with outer surfaces of side wall  4126 . The user may move release  4104  by engaging engagement element  4112 . The user may move release  4104  by pressing button  4026 . 
     Engagement element  4112  may be disposed within a region defined by front side  4124  and side wall  4126 . 
     Latch  4004  may include an arrangement analogous to that of latch  4006 . 
     In the event that sections  4132  and  4134  of side wall  4126  are flush against panels such as  804  and  806 , fixture head  4000  may be released from the fixture support by pushing button  4026 . If section  4128  of side wall is inaccessible, fixture head  4000  may be released from the fixture support by accessing engagement element  4112  to move release  4104  toward section  4130 . 
       FIG.  42    shows fixture head  4000  with latches  4004  and  4006  removed. Frame  4002  may support circuit board  4202 . Pin pair  4016  is shown in electrical communication with circuit board  4202 . Circuit board  4202  may receive power from pin pairs  4014  and  4016 . Circuit board  4202  may receive communication signals from pin pairs  4012  and  4018 . Circuit board  4202  may include a power distribution circuit (not shown). Circuit board  4202  may include a communication signal distribution circuit (not shown). 
       FIG.  43    shows illustrative fixture  4300 . Fixture  4300  may include fixture head  4302 . Fixture  4300  may include cabinet  4304 . Fixture  4300  may include arm  4306 . Fixture  4300  may include light  4308 . 
     Fixture head  4302  may have one or more features in common with fixture head  4000 . 
     One or more of cabinet  4304 , arm  4306  and light  4308  may include circuits, devices, or both for changing fixture parameters of fixture  4300  based on communication signals or using power received from fixture head  4302 . 
     Cabinet  4304  may include a pan motor for rotating arm  4306  about axis L 1  through pan angle p. Light  4308  may include a tilt motor for rotating light  4308  about axis L 2  through tilt angle t 1 . Light  4308  may include a current-responsive lens for changing a beam spread angle β of a beam emerging from light  4308  along axis L 3 . 
     Light  4308  may include recess  4310 . Arm  4306  may occupy some or all of recess  4310  when tilt angle t 1 =0. 
       FIG.  44    shows in part cabinet  4304  and arm  4306 . Electric motor  4402  may drive worm screw  4404 . Worm screw  4404  may drive worm wheel  4406 . Wheel  4408  may be rigidly fixed to worm wheel  4406 . Wheel  4408  may engage pan wheel  4410 . Pan wheel  4410  may be coaxial with arm  4306 . Pan wheel  4410  may be fixed to and rotatable with arm  4306 . Compression nut  4412  may be threadingly engaged with arm  4306 . Compression nut  4412  may pressurize washer  4414 . Compression nut  4412  may pressurize washer  4416 . Compression nut  4412  may pressurize washer  4430 . 
     One or both of washers  4414  and  4430  may have a non-circular opening that matches a non-circular cross-section of arm  4306 . One or both of washers  4414  and  4430  may be pressed against and cause engagement of pan wheel  4410  with arm  4306 . Straight edges  4432  and  4434  may engage with corresponding straight sides  4436  and  4438  of neck  4440  of arm  4306 . Washer  4414  may have one or more straight edges analogous to straight edges  4432  and  4434 , and configured to engage sides such as  4436  and  4438 . Washers  4414  and  4416  may cause arm  4306  to rotate under torque from wheel  4410 . 
     Cabinet  4304  may include boss  4442  (partially shown). Washer  4416  may include notch  4444  (partially shown). Boss  4442  may limit rotation of washer  4416  about arm  4306 . Detent  4446  of washer  4416  may interfere with tab  4448  of washer  4430 . Thus, rotation of arm  4306  in one or both directions about axis L 1 , by interference between tab  4448  and detent  4446  to the extent that boss  4442  interferes with washer  4416 . 
     Cabling  4418  may deliver power from fixture head  4302 . Cabling  4418  may provide exchange of communication signals with a microprocessor such as  516 , which may be disposed in cabinet  4304 . 
     Cabling  4420  may deliver power to devices in light  4308 . Cabling  4420  may provide exchange of communication signals with a microprocessor such as  516 , which may be disposed in cabinet  4304 . The microprocessor may include a current-adjustable-lens controller. 
     Step  4426  in cabinet  4304  may provide a reactive force to resist corresponding step  4424  in arm  4306  under tension from compression nut  4412 . Step  4424  and step  4426  may act as bearing surface when arm  4306  rotates. 
     Arm  4306  may include holes  4421  and  4423 . Holes  4421  and  4423  may receive an axle for rotation of light  4308  about axis L 2 . 
       FIG.  45    shows in part arm  4306  and light  4308 . Tilt wheel  4502  may be rigidly fixed to arm  4306  by axle  4504  along axis L 2 . Hole  4506  in tilt wheel  4502  may receive a pin (not shown). The pin may be disposed in hole  4506  and in corresponding holes in arm  4306 . 
     Electric motor  4508  may drive worm screw  4510 . Worm screw  4510  may drive worm wheel  4512 . Pin  4513  may support worm wheel  4512 . Wheel  4512  may engage tilt wheel  4502 . When worm wheel  4512  turns, axis L 3  may be moved to a different tilt angle t 1  relative to L 1 . 
     LED emitter  4514  may emit light. Reflector surface  4516  may intensify the light. Static lens  4518  may form a beam centered along axis L 3  from the light. Static lens  4518  may include a convex surface. The beam may pass through liquid crystal lens  4520 . Lens  4520  may include a liquid crystal material that converges light based on an electric field applied to the material. Frame  4522  may apply the electric field to lens  4520 . Light  4308  may include shroud  4524 . Clip  4526  may hold shroud  4524  in place. 
     Frame  4528  may support axle  4504  and pin  4513 . 
     Cabling  4418  may deliver power from fixture head  4302 . Cabling  4418  may provide exchange of communication signals with a microprocessor such as  516 , which may be disposed in cabinet  4304 . 
     Cabling  4530  may include an extension of some or all of cabling  4420 . 
     Frame  4522  may receive current from cabling  4530 . 
       FIGS.  46 - 49    show illustrative power supply box  4601 , illustrative lamp body  4602 , and illustrative lamp arm assembly  4603 . Power supply box  4601  may have one or more features in common with fixture head  4000 . Power supply box  4601  may have one or more features in common with cabinet  4304 . Lamp body  4602  may have one or more features in common with light  4308 . Lamp arm assembly may have one or more features in common with arm  4306 . 
     Power supply box  4601  may include first driving assembly  4704 . Lamp body assembly  4602  may include second driving assembly  4705 . One end of lamp arm assembly  4603  may be rotatably connected to power supply box  4601 . The other end of the lamp arm assembly  4603  may be rotatably connected to lamp body assembly  4602 . First driving assembly  4704  may be used to drive lamp arm assembly  4603  to rotate. Second driving assembly  4705  may be used to drive lamp body assembly  4602  to rotate. The top of power supply box  4601  may be provided with fixing blocks  4627 . Each fixing block  4627  may include sliding protrusions  4628 . Sliding protrusions  4628  may be configured to slidingly retract and extend from power supply box  4601  for installation or deinstallation of power box  4601  in a fixture support such as fixture support  800 . First driving assembly  4704  may drive lamp arm assembly  4603  to rotate. Second driving assembly  4705  may drive lamp body assembly  4602  to rotate. The position of lamp body assembly  4602  and an angle (an “irradiation angle”) of a beam from lamp body assembly  4602  may thus be controlled by a motor. Power supply box  4601  may include control circuit board module  4822 . Control circuit board module  4822  may be in electrical communication with first driving assembly  4704  and second driving assembly  4705 . Control circuit board module  4822  may include a wireless communication module. The wireless communication module may be configured to communicate with a control module such as  304  or an input such as  306 . 
     The top of fixing block  4627  may provided with magnet  4629 . Fixing block  4627  may thus be attached to the fixture support by the magnet  4629 . 
     First driving assembly  4704  may include first drive motor  4706 . First driving assembly  4704  may include first gear box  4707 . An output shaft of first drive motor  4706  may be connected to first encoder  4808 . First gear shaft  4809  may be rotatably arranged in first gear box  4707 . First transmission gear  4810  may be in meshing transmission connection with first encoder  4808 . First transmission gear  4810  may be disposed over the outer circumference of one end of first gear shaft  4809 . Second transmission gear  4811  may be disposed over the outer circumference of the other end of first gear shaft  4809 . First lamp arm gear  4712  may be in meshing transmission connection with second transmission gear  4811 . First lamp arm gear  4712  may be fixedly disposed over the outer circumference of one end of the lamp arm assembly  4603 . First gear box  4707  may be disposed in power supply box  4601 . First drive motor  4706  may be disposed on first gear box  4707 . First drive motor  4706  may drive first encoder  4808  to rotate. First drive motor  4706  may drive first transmission gear  4810  to rotate. Second transmission gear  4811  may thus be driven to rotate through the cooperation of first gear shaft  4809  the second transmission gear  4811 . This may cause rotation of first lamp arm gear  4712  and lamp arm assembly  4603 . 
     A center element of a lower end surface of the power supply box  4601  may include a rotating hole  4713 . A lamp arm bearing  4814  may be disposed in the rotating hole  4713 . One end of lamp arm assembly  4603  may be rotatably connected to rotating hole  4713  through lamp arm bearing  4814 . 
     The other end of lamp arm assembly  4603  may include second lamp arm gear  4715 . Second driving assembly  4705  may include second drive motor  4716 . Second driving assembly  4705  may include second gear box  4717 . Second gear shaft  4918  may be rotatably arranged in second gear box  4717 . Third transmission gear  4919  may be disposed over the outer circumference of second gear shaft  4918 . An output shaft of second drive motor  4716  may be connected to second worm  4920 . Second worm  4920  and second lamp arm gear  4715  may be respectively in meshing transmission connection with third transmission gear  4919 . Second gear box  4717  may be disposed in lamp body assembly  4602 . Second drive motor  4716  may be disposed on second gear box  4717 . Second drive motor  4716  may drive second worm  4920  to rotate. Second drive motor  4716  may drive third transmission gear  4919  to rotate. Rotational control of lamp body assembly  4602  may be accomplished through the cooperative meshing transmission of third transmission gear  4919  and second lamp arm gear  4715 . 
     Pocket groove  4621  may be disposed on one side of an outer wall of lamp body assembly  4602 . Pocket groove  4621  may be arranged complementarily with lamp arm assembly  4603 . Pocket groove  4621  receive lamp arm assembly  4603  to facilitate angle adjustment between the lamp arm assembly  4603  and the lamp body assembly  4602 . 
     Lamp body assembly  4602  may include light source  4923 . Light source  4923  may be in electrical communication with control circuit board module  4822 . Current supplied by control circuit board module  4822  to light source  4923  assembly may be adjusted to adjust the brightness of light source  4923  assembly. The brightness of light source  4923  may be controlled through a control module such as  304  or an input such as  306 . 
     Lamp body assembly  4602  may include lens  4924 . Lens  4924  may be electrically connected to the control circuit board module  4822 . The transparency of lens  4924  may be controlled through a control module such as  304  or an input such as  306 . A beam angle of lamp body assembly may be controlled through a control module such as  304  or an input such as  306 . 
     A first encoder  4725  may be disposed at a tail portion of the first drive motor  4706 . First encoder  4725  may be configured to record a rotational position of the first drive motor  4706 . Second encoder  4726  may be arranged at a tail portion of second drive motor  4716 . Second encoder  4726  may be configured to record a rotational position of second drive motor  4716 . Recordation of a rotational position may provide a reference for performing a further rotation that is defined relative to a recorded rotational position. 
       FIG.  50    shows illustrative fixture  5000 . Fixture  5000  may include fixture head  5002 . Fixture  5000  may include cabinet  5004 . Fixture  5000  may include arm  5006 . Fixture  5000  may include light  5008 . 
     Fixture head  5002  may have one or more features in common with fixture head  4000 . 
     One or more of cabinet  5004 , arm  5006  and light  5008  may include circuits, devices, or both for changing fixture parameters of fixture  5000  based on communication signals or using power received from fixture head  5002 . 
     Fixture head  5002  and cabinet  5004  may form base  5010 . Fixture head  5002  may include detent  5012 . Fixture head  5002  may have a detent (not shown) on a side of fixture head  5002  opposite the side including detent  5012 . Detent  5012  and the corresponding opposite detent in operation may be supported by ridges  1038  and  1040 . 
     Light  5008  may include housing  5014 . Housing  5014  may include recess  5015 . Recess  5015  may receive arm  5006  when housing  5014  is tilted relative to arm  5006 . 
       FIG.  51    shows that cabinet  5004  may include turntable  5102 . Turntable  5102  may include a joint that pivotably links turntable  5102  to arm  5006 . Arm  5006  may include central axis L 4 . Turntable may be rotatable about axis L 5  through pan angle p when arm  5006  is clear of cabinet  5004 . Turntable  5102  may rotate through pan angle p to permit rotation of light  5008 . Arm  5006  may be rotated about axis L 6  through swing angle s. When swing angle s is 180° and pan angle p is 0, arm  5006  may be seated in recess  5104  in fixture head  5002 . 
     Light  5008  may include a joint (not shown) on axis L 7  that pivotably links light  5008  to arm  5006 . The joint may permit rotation of light  5008  relative to arm  5006  about axis L 7  through tilt angle t 2 . When tilt angle t 2 =0, arm  5006  may be seated in recess  5015 . 
     Rotation of annulus  5106  may displace a lens (not shown) in light  5008  relative to an LED emitter (not shown) in light  5008 . The displacement may change beam spread angle β 2 . 
       FIG.  52    shows partially turntable  5102  in cabinet  5004 . Pin  5202  may extend along axis L 6  from turntable  5102 . Arm  5006  (not shown) may be rotatable around pin  5202 . 
     A half of turntable  5102  that is not shown in the view of  FIG.  52    may mirror the half of turntable  5102  that is shown in the view. 
     Turntable  5102  may conform to well  5204  with suitable tolerance for rotation. Cabinet  5004  may include shelf  5206 . Shelf  5206  may retain turntable  5102  in a fixed position relative to cabinet  5004  along axis L 5 . Shelf  5206  may be the sole element of cabinet  5004  that retains turntable  5102  in a fixed position relative to cabinet  5004  along axis L 5 . 
     Turntable  5102  may include runner  5208 . Turntable  5102  may include washer  5218 . Runner  5208  may be fixed to body  5212  of turntable  5102  by fasteners  5214  and  5216 . Washer  5218  may be disposed between shelf  5206  and body  5212 . Tension from fasteners  5214  and  5216  may compress shelf  5206  and washer  5218  between runner  5208  and body  5212 . The tension may provide enough frictional resistance to prevent turntable  5102  from inadvertently rotating about axis L 5  but permit the user to conveniently manually rotate turntable  5102 . 
     Washer  5218  may include tab  5220 . Cabinet  4304  may include a projection that may interfere with tab  5220  when washer  5218  rotates. The projection may prevent rotation of washer  5218  when turntable  5102  rotates. 
     Fixture head  5002  may include circuit board  5222 . Circuit board  5222  may be in electrical communication with pins such as  4010 . 
     Bay  5224  may provide passage for cabling (not show) for light  5008 . 
       FIG.  53    shows partially arm  5006  and light  5008 . Arm  5006  may swing relative to light  5008  about pin  5302 , along axis L 7 . Housing  5014  may include bench  5304 . Bench  5304  may support LED emitter  5306 . Housing  5014  may include threads  5308 . Threads  5308  may line annular recess  5309 . Threads  5308  may support collar  5310 . Collar  5310  may be threadingly engaged with threads  5308 . Collar  5310  may be manually moved up and down along axis L 8  by rotating collar  5310  in threads  5308 . Moving collar  5310  up or down along axis L 8  changes the distance between lens  5312  and LED emitter  5306 . The change in distance changes beam spread angle β 2 . 
     Passageway  5314 , pass-through  5316 , and hole  5318  may provide for passage of cabling from fixture head  5002  to LED emitter  5306 . 
     Housing  5014  may include groove  5320 . Clip  5322  may be disposed in groove  5320 . Clip  5322  may be shaped and biased to prevent collar  5310  from exiting threads  5308  by interfering with flange  5324  of collar  5310  while remaining lodged in groove  5320 . 
     Honeycomb  5326  may reduce glare from a beam emitted from LED emitter  5306 . 
     Housing  5014  may include lip  5328 . Housing  5014  may be retractable into a U-channel such as U-channel  1052 . When housing  5014  is retracted into U-channel  1052 , lip  5328  may be drawn above a distal edge of the U-channel, such as distal edge  1056  (schematically shown in broken line). When housing  5014  is retracted into U-channel  1052 , crown  5330  of housing  5014  may abut or nearly abut a docking tier such as docking tier  814  (schematically shown in broken line). 
       FIG.  58    shows illustrative fixture  5800 . Fixture  5800  may include fixture head  5802 . Fixture  5800  may include cabinet  5804 . Fixture  5800  may include cord  5806 . Fixture  5800  may include light  5808 . 
     Fixture head  5802  may have one or more features in common with fixture head  4000 . 
     One or both of cabinet  5804  and light  5808  may include circuits, devices, or both for changing fixture parameters of fixture  5800  based on communication signals or using power received from fixture head  5802 . 
     Fixture head  5802  and cabinet  5804  may form base  5810 . 
     Light  5808  may include housing  5814 . 
     Light  5808  may be positioned along axis L 9  of cord  5806  at a height h above a reference level r. Level r may correspond to a structure, a floor, the ground or any other reference object. Axis L 9  may define radial direction R. 
       FIGS.  54 - 57    show illustrative radiator  5401 , condensing cover  5402  and clamping ring  5503 . Radiator  5401  may have one or more features in common with light  4308 . Radiator  5401  may have one or more features in common with housing  5014 . Condensing cover  5402  may have one or more features in common with shroud  4524 . Condensing cover  5402  may have one or more features in common with annulus  5106 . Clamping ring  5503  may have one or more features in common with clip  5322 . 
     An inner wall of radiator may include internal thread  5411 . Condensing cover  5402  may include external thread  5521 . Clamping ring  5503  may be disposed near the inner wall of radiator  5401 . Clamping ring  5503  may be rotatably mounted to internal thread  5411 . Condensing cover  5402  may be screwed to radiator  5401  via external thread  5521 . 
     When condensing cover  5402  is rotated for focusing, the position of condensing cover  5402  may be e limited by clamping ring  5503  to prevent condensing cover  5402  and a lens associated therewith from being detached from radiator  5401  due to excessive rotation. 
     Condensing cover  5402  may include mounting element  5522 . Condensing cover  5402  may include connecting element  5523 . Condensing cover  5402  may include fixing element  5524 . Mounting element  5522  and fixing element  5524  may be arranged at two ends of connecting element  5523 . External thread  5521  may be arranged on mounting element  5522 . Mounting element  5522  may be rotatably mounted to the radiator  5401  via external thread  5521 . External thread  5521  on mounting element  5522  may be screwed to internal thread  5411  of radiator  5401 . 
     Clamping ring  5503  may protrude inward to form disassembling element  5631 . When clamping ring  5503  is installed, first condensing cover  5402  may be rotated into radiator  5401 , and then clamping ring  5503  may be placed in internal thread  5411  of radiator  5401  in a surrounding manner. For disassembly, tweezers or another similar item may be used to clamp disassembling element  5631  and withdraw clamping ring  5503  from internal thread  5411 . When a light source or lens needs to be replaced, disassembly may be performed directly from the front of condensing cover  5402 . 
     An outer diameter of connecting element  5523  may gradually decrease from left to right (along a direction from condensing cover  5402  to radiator  5401 ). This may expose a gap between condensing cover  5402  and radiator  5401 . The gap may facilitate heat dissipation. 
     An outer diameter of fixing element  5524  may be greater than an inner diameter of radiator  5401 . When rotated to the deepest position, fixing element  5524  may abut against radiator  5401 . 
       FIG.  59    shows that light  5808  may include lens  5902 . Light  5808  may include shield  5904 . Shield  5904  may be extendable away from housing  5814  along axis L 9 . Shield  5904  may be rotated relative to housing  5814  to adjust beam spread angle β 3 . Shield  5904  may be translated along axis L 9  to prevent light from light  5808  from spreading outside a targeted area. 
       FIG.  60    shows illustrative gripper  6002 . Gripper  6002  may include tapered tube  6004 . Tube  6004  may include cannula  6006 . Cannula  6006  may be cylindrical. Cord  5806  may be disposed in cannula  6006  with a tolerance sufficient to permit sliding of cord  5806  through cannula  6006  with a small amount of friction. Gripper  6002  may include bumpers such as  6008  and  6010 . Bumpers  6008 ,  6010  and a third bumper (not shown) may be arranged about L 9  axis. The bumpers may be arranged symmetrically, such as at 120° arc from each other, about the axis. The bumpers may be captured in sockets  6012 ,  6014  and a third socket (not shown), respectively. The sockets may allow the bumpers to translate radially in an out relative to axis L 9 . When positioned inwardly, the bumpers may contact cord  5806 . In the absence of an inward radial force on the bumpers, the bumpers may allow cord  5806  to translate freely along L 9  relative to housing  5814 . When an inward radial force is applied to the bumpers, the bumpers may seize cord  5806  and prevent cord  5806  from translating along L 9  relative to housing  5814 . 
     When cord  5806  is drawn upward relative to housing  5814 , the small amount of friction may draw tube  6004  upward inside cannulated tapered bolt  6016 . Taper  6019  may apply an inward radial force to the bumpers. The relative movement between tube  6004  and housing  5814  may be generated by the user. The relative movement between tube  6004  and housing  5814  may be generated by a gravitational pull on light  5808 . 
     Spring  6018  may be anchored in bushing  6020 . Spring  6018  may be engaged with tube  6004  at narrow section  6022  of tube  6004 . Spring  6018  may be normally in tension. Spring  6018  thus urges tube  6004  down, away from taper  6019 . Spring  6018  thus acts to release cord  5806  from gripper  6002 . Tension in spring  6018  may be selected to offset some but not all of the gravitational force on light  5808  so that cord  5806  is normally seized in gripper  6002 . The user may adjust height h of light  5808  by manually urging cord  5806  down in gripper  6002  and overcoming the tendency of the bumpers to continue to seize cord  5806  even after the user manually supports light  5808  and relieves the gravitational force. 
     The user may increase h by feeding cord  5806  down through gripper  6002 . The user may decrease h by drawing cord  5806  up through gripper  6002 . The seizing force of the bumpers may be insufficient to prevent manual withdrawal of cord  5806  from gripper  6002 . The user may manually press down on top  6030  of tube  6004  to release the bumpers from cord  5806 . 
     Shelves  6024  and  6026  may support bolt  6016 . Housing  5814  may support shelves  6024  and  6026 . Interior  6028  of housing  5814  may store lengths of cord  5806 . 
       FIGS.  61 - 66    show an illustrative shifting mechanism for suspending a cord. The cord may be used to suspend a light fixture. The fixture may have one or more features in common with fixture  5800 . The cord may have one or more features in common with cord  5806 . The shifting mechanism may include main body  6101 . The shifting mechanism may include hanging member  6302 . The shifting mechanism may include connector  6103 . The shifting mechanism may include a reset member. Hanging member  6302  may be movably connected to main body  6101 . Two ends of the reset member may be connected to hanging member  6302  and the main body  6101 , respectively. A top of main body  6101  may be detachably connected to connector  6103 . Main body  6101  may include open slot  6106 . Main body  6101  may include moving slot  6105 , in which hanging member  6302  may move. Moving slot  6105  may be in communication with open slot  6106 . 
     Main body  6101  may be fixed to a structure such as S. Main body  6101  may be fixed to a fixture such as fixture  5800 . Hanging member  6302  may be rotated so that hook  6211  is outside main body  6101 . The cord may be inserted into open slot  6106 . A loop of the cord may be inserted into open slot  6106 . Hanging member  6302  may be rotated back into main body  6101 . Hanging member  6302  may engage the cord inside main body  6101 . Hanging member  6302  may engage the loop inside main body  6101 . Main body  6101  may be tightened against connector  6103  using threaded connecting portion  6307  and internal thread  6408 . The tightening may prevent rotating shaft portion  6310  from rotating. The cord may thus be “locked” in main body  6101  at a position that leaves a desired amount of cord hanging between the structure and the fixture. 
     Hanging member  6302  may be movably connected with main body  6101 . During use, hanging member  6302  may be pulled out main body  6101  from moving slot  6105  by a human hand. The cord may then be extended from open slot  6106  to a position where main body  6101  matches hanging member  6302 . Hanging member  6302  may be pushed into main body  6101 . Hanging member  6302  may hook the cord to effect the hanging and placement of the cord. Connector  6103  may be fixed to the ceiling by a mounting element such as a screw and a bolt. Main body  6101  the connector  6103  may be detachably connected to facilitate mounting. That is, adjustment and mounting may be performed after shifting to a suitable position based on environmental structures. The reset member may pull hanging member  6302  to prevent loosening of the hanging member  6302 . This may ensure the stability of hanging and placement of the cord, and facilitating the reset of hanging member  6302 . 
     The top of main body  6101  may include a threaded connecting portion  6307 . Threaded connecting portion  6307  may include an external thread. An inner wall of connector  6103  may include internal thread  6408  that matches the external thread. Mounting hole  6209  may penetrate through connector  6103 . Connector  6103  and main body  6101  thus may be disassembled and assembled. Mounting hole  6209  may cooperate with an assembly screw and bolt to engage a ceiling or other structure such as structure S. Connector  6103  may be locked through the cooperation of an external connecting member and mounting hole  6209 . 
     Hanging member  6302  may include rotating shaft portion  6310 . Hanging member  6302  may include hook portion  6211 . Hanging member  6302  may include protrusion  6112 . Main body  6101  may include rotating slot  6313 . Rotating slot  6313  may rotates cooperatively with rotating shaft portion  6310 . The reset member may be disposed in rotating slot  6313 . Two ends of the reset member may be connected to rotating shaft portion  6310  and an inner wall of rotating slot  6313 , respectively. The hook portion  6211  may be connected to a lower end of the rotating shaft portion  6310 . Protrusion  6112  may be connected to an outer wall of hook portion  6211 . Through protrusion  6112 , an operator may pull protrusion  6112  to pull out hook portion  6211  of hanging member  6302 , and rotating shaft portion  6310  may rotate in rotation slot  6313  to effect moving of the hook portion  6211 . Under action of the reset member, rotating shaft portion  6310  may be pressed tightly to ensure that the position of the rotating shaft portion  6310  does not easily loosen, and that hook portion  6211  hangs the cord stably. 
     Rotating shaft portion  6310 , hook portion  6211 , and protrusion  6112  may be integrally formed. 
     The reset member may be reset spring  6604 . Two reset springs  6604  may be provided, respectively, at two ends of rotating slot  6313 . Reset springs  6604  may match the two ends of rotating shaft portion  6310  for maintaining the balance of the two ends of the rotating shaft portion  6310  and reset stability. 
       FIG.  67    shows shield  5904  in housing  5814 . Light  5808  may include lens  6702 . Lens  6702  may form a beam from light emitted by LED emitter  6704 . Lens well  6706  may be fixed to shelf  6708 . Shelf  6708  may be fixed to housing  5814 . Lens positioning bushing  6710  may be disposed in well  6706 . Bushing  6710  may rotate about axis L 9  in well  6706 . Well  6706  may include slots such as  6712 . Slot  6712  may be helical about axis L 9 . Bushing  6710  may include slots such as  6714  and  6716 . Slots  6714  and  6716  may be parallel to axis L 9 . As bushing  6710  is rotated relative to well  6706 , intersections between the helical and parallel slots may move along axis L 9 . Projections such as  6718  from lens table  6720  may be disposed in the intersections. Thus, relative rotation between bushing  6710  and well  6706  may move lens  6702  along axis L 9  relative to emitter  6704 . This may change beam spread angle β 3 . Rotation of shield  5904  about axis L 9  may cause interference of an edge (not shown) of shield  5904  with a catch of bushing  6710 . The interference may cause the relative rotation. 
     Fingers  6722  and  6724  may be biased radially outward from axis L 9  to maintain contact between fingers  6722  and  6724  with inner surface  6726  of housing  5814 . The user may manually move shield  5904  may be up and down along axis L 9 . When the user releases shield  5904 , friction between fingers  6722  and  6724  and surface  6726  may maintain the position of shield  5904  relative to housing  5814 . Band  6728  in housing  5814  may limit the downward extension of shield  5904 . Foot  6730  of bushing  6710  may limit the upward insertion of shield  5904 . 
     Sheath  6732  may provide lateral support to cord  5806 . 
       FIG.  68    shows edges  6802  and  6804  of shield  5904  that may engage with catches  6806  and  6808  of bushing  6710 . Shield  5904  may thus move longitudinally along axis L 9  without rotating bushing  6710 . Shield  5904  may be rotated about axis L 9  without moving longitudinally along axis L 9 . 
       FIGS.  69 - 76    show illustrative fixture support  6901  and at least two illustrative lamp bodies  6902 . Fixture support  6901  may have one or more features in common with fixture support  310 . Lamp bodies  6902  may have one or more features in common with fixture  316 . Ends of each of the lamp bodies  6902  may be detachably connected to end covers  6903 . Lamp body  6902  may be slidably arranged in fixture support  6901 . Adjacent ends of two adjacent lamp bodies  6902  may abut each other. Left and right ends of fixture support  6901  may include lamp entrances  7104 . The bottom of fixture support  6901  may include exposure port  6905 . Lamp bodies  6902  may be exposed at exposure port  6905 . End cover  6903  may be detachably connected to lamp body  6902 . Two or more lamp bodies  6902  may be installed in fixture support  6901 . After end covers  6903  are disassembled, lamp bodies  6902  abut each other in fixture support  6901  to form a seamless joint effect. The structure may be stable and reliable, and light leakage may be avoided. Lamp body  6902  may be pushed into fixture support  6901  from lamp entrances  7104  at the left and right ends of fixture support  6901  for installation. Exposure port  6905  may provide for light transmission. 
     Lamp body  6902  may include lamp housing  6906 . Lamp body  6902  may include light-emitting cover  6907 . Lamp body  6902  may include light-emitting body  6908 . Light-emitting body  6908  may be disposed on lamp housing  6906 . Light-emitting cover  6907  may be disposed at the bottom of lamp housing  6906 . Light of the light-emitting body  6908  may face light-emitting cover  6907 . End cover  6903  may be detachably connected to lamp housing  6906 . 
     Adjacent ends of light-emitting covers  6907  of two adjacent lamp bodies  6902  may abut each other. The seamless joint between two or more lamps assembled in fixture support  6901  may reduce or avoid light leakage. The seamless joint between two or more lamps assembled in fixture support  6901  may reduce or avoid light leakage may have good structural integrity. 
     Sides of the top end of light-emitting cover  6907  may include clamping strips  7309 . Sides of an inner wall of the bottom of lamp housing  6906  may include clamping slots  7110 . Clamping slots  7110  may match clamping strips  7309 . This may provide clamping of light-emitting cover  6907  and lamp housing  6906 . 
     Sides of end cover  6903  may include buckling blocks  7411 . Sides of the inner wall of the bottom of lamp housing  6906  may include buckling slots  7312 . Buckling slots  7312  may fit buckling blocks  7411 . The detachable connection of end cover  6903  may be effected through cooperation of buckling block  7411  and buckling slot  7312 . This may facilitate the assembly and disassembly of the end cover  6903 . This may facilitate replacement of a lamp. 
     Ends of the top of lamp housing  6906  may include fixing blocks  6913 . Sides of the fixing block  6913  may include sliding protrusions  6914 . Sides of an inner wall of fixture support  6901  may include sliding slots  7121 . Sliding slots  7121  may match sliding protrusions  6914 . Cooperation of sliding protrusion  6914  and sliding slot  7121  may provide for the sliding of lamp body  6902  along the inner wall of fixture support  6901 . 
     One end of fixing block  6913  may include button  6915 . Button  6915  may be connected to pushing block  7516 . Pushing block  7516  may be slidably arranged in fixing block  6913 . An end of pushing block  7516  away from button  6915  may be connected to reset spring  7517 . An end of reset spring  7517  away from pushing block  7516  may be connected to an inner wall of fixing block  6913 . An end of sliding protrusion  6914  may extend into fixing block  6913 . An end of sliding protrusion  6914  may include limiting sliding column  7618 . Sides of pushing block  7516  may include limiting sliding slots  7519 . Limited sliding slots  7519  may match limiting sliding columns  7618 . Limiting sliding columns  7618  may be slidably arranged in limiting sliding slots  7519 . Sides of fixing block  6913  may include through-holes. An end of sliding protrusion  6914  may protrude from the through-hole. The bottom of fixing block  6913  may include pushing slot  7520 . Pushing block  7516  may be slidably arranged on pushing slot  7520 . When the lamp body  6902  is to be taken out of fixture support  6901 , button  6915  may be pressed so that pushing block  7516  moves along pushing slot  7520 , and sliding protrusion  6914  is driven, by limiting sliding slot  7519 , to be retracted from the through-hole into fixing block  6913 . At this time, sliding protrusion  6914  may be separated from sliding slot  7121 . This may facilitate removal of lamp body  6902  from fixture support  6901 . When button  6915  is released, under action of reset spring  7517 , reset spring  7517  may drive the pushing block  7516  to reset. Button  6915  may reset. Then reset spring  7517  may drive sliding protrusion  6914  to extend from the through-hole to effect the reset. Sliding protrusion  6914  and sliding slot  7121  may be slidingly matched to facilitate sliding connection between lamp body  6902  and the inner wall of fixture support  6901 . 
     Displacement of two or more lamp bodies  6902  may be limited by abutting each other. Clamping columns and clamping holes for cooperative limiting may be provided at positions corresponding to two ends of lamp housing  6906  or two ends of light-emitting cover  6907 . Magnets may be arranged at ends of lamp housing  6906  or at positions corresponding to ends of light-emitting cover  6907 . Abutting cooperation and seamless joints may be provided by mutual attraction of the magnets. 
       FIGS.  77 - 80    show illustrative lamp housing  7701 , light source  7802 , and polarizing lens  7803 . One or more of lamp housing  7701 , light source  7802 , and polarizing lens  7803  may be part of a fixture such as fixture  316 . Mounting slot  7904  may be recessed on a side of a lower end surface of lamp housing  7701 . Light source  7802  may be disposed in mounting slot  7904 . Polarizing lens  7803  may be disposed on a lower end surface of light source  7802 . Light blocking element  7805  may be provided on a side of the lower end surface of lamp housing  7701 . Light blocking element  7805  may include reflective film  7806 . Arc-shaped reflective surface  7807  may be provided on a side of the lower end surface of lamp housing  7701 . Light exit port  7808  may be defined between arc-shaped reflective surface  7807  and light blocking element  7805 . Light emitted by light source  7802  may passes through polarizing lens  7803 . The light then may be emitted from light exit port  7808 . Light source  7802  may be arranged in mounting slot  7904 . After the light passes through polarizing lens  7803 , the light may propagate from light exit port  7808 . Light blocking element  7805  may be provided. Reflective film  7806  may be provided on light blocking element  7805 . Reflective film  7806  may reflect the light away from light blocking element  7805 . Arc-shaped reflective surface  7807  may reflect the light downward. The guiding of light from light source  7802  may reduce or avoid glare. 
     Reflective film  7806  may include a diffuse reflective film. 
     Arc-shaped reflective surface  7807  may span an arc of less than 90°. 
     A lower end of mounting slot  7904  may be provided with limiting slot  7909 . An upper end of the polarizing lens  7803  may be provided with limiting element  7910 . Limiting element  7910  may be accommodated in limiting slot  7909 . Limiting slot  7909  and limiting element  7910  may limit polarizing lens  7803  to prevent polarizing lens  7803  from loosening. 
     Ends of lamp housing  7701  may include detachable cover plates  7715 . Sides of an inner wall of the lamp housing  7701  may include clamping slots  7816 . An inner side of cover plate  7715  may include fixing sheet  8017 . Sides of fixing sheet  8017  may include elastic clamping sheets  8018 . An outer wall of elastic clamping sheet  8018  may include arched bulge  8019 . When cover plates  7715  are assembled to the ends of lamp housing  7701 , elastic clamping sheet  8018  may be aligned with clamping slot  7816  and snapped into clamping slot  7816 . Elastic clamping sheet  8018  and arched bulge  8019  may be matched so that elastic clamping sheet  8018  may be firmly fixed in clamping slot  7816 . Cover plates  7715  may abut the end surfaces of lamp housing  7701 . When cover plate  7715  is to be disassembled, cover plate  7715  may be pulled so that elastic clamping sheet  8018  separates from clamping slot  7816 . The end cover may be disassembled by bare hands. 
     Fixture support  7811  may support lamp housing  7701 . Ends of a top of lamp housing  7701  may include fixing blocks  7712 . Sides of fixing block  7712  may include sliding blocks  7713 . An inner wall of fixture support  7811  may include slideways  7814 . Sliding blocks  7713  may be slidably arranged in slideways  7814 . This may facilitate installation and removal of cover plate  7715 . When the lamp housing  7701  is to be assembled into fixture support  7811 , cover plate  7715  may be removed alone, and lamp housing  7701  may be accommodated in fixture support  7811 . Installation of lamp housing  7701  can be achieved through cooperation of slideway  7814  and sliding block  7713 , when disposed between the fixture support  7811  and lamp housing  7701 . During installation of two or more lamp housings  7701  in fixture support  7811 , the lamp housings  7701  may be disposed in abutment with each other so that they appear as a continuous whole, with no dark areas or visual discontinuity. 
       FIG.  81    shows illustrative configuration  8100  of fixtures  316 ,  8102 ,  8104  and  8106  (indexed below as “a,” “b,” “c” and “d,” respectively) in connection with architecture  300 . Configuration  8100  creates scene S 1 . Scene S 1  may include object O. Object O may be the target. Object O may include target  8108 . Ambient light AL 1  may illuminate object O. Ambient light may include light from sources other than fixtures  316 ,  8102 ,  8104  and  8106 . Ambient light may include diffuse light. Ambient light may include direct light. Ambient light may include light originating outside, such as that entering through window W. 
     The user may instruct architecture  300  to illuminate object O based on one or more selected beam parameters. Pitch and tilt angle pairs of the fixtures (viz., (p a     1   , t a     1   ), (p b     1   , t b     1   ), (p c     1   , t c     1   ), (p d     1   , t d     1   ), . . . ) may be set by locating target  8108 . Tilt angles may be defined in reference to vertical v, which may be a plumb line. 
       FIG.  82    shows illustrative configuration  8100  of fixtures  316 ,  8102 ,  8104  and  8106  (indexed below as “a,” “b,” “c” and “d,” respectively) in connection with architecture  300  after object O has been moved to a second location. Configuration  8100  creates scene S 2 . Ambient light AL 2  may illuminate object O. 
     The user may instruct architecture  300  to illuminate object O based on one or more selected beam parameters. Pitch and tilt angle pairs of the fixtures (viz., a (p a     2   , t a     2   ), (p b     2   , t b     2   ), (p c     2   , t c     2   ), (p d     2   , t d     2   ), . . . ) may be reset by locating target  8108  in scene S 2 . 
       FIG.  83    shows schematic transform  8300  of a fixture such as  316  between scene S 1 , with object O at location x 1 , to scene S 2 , with objection O at location x 2 . As configured for scene S 1 , fixture  316  has bearing b 1  and beam spread angle β 4 . At the height z O , corresponding to object O, the fixture  316  beam has horizontal area A 4 . When object O is moved to location x 2 , for scene S 2 , architecture  300  may change the fixture  316  bearing to b 2  to direct the beam to object O at x 2 . Architecture  300  may perform calculations to derive a beam spread angle β 4  that results in horizontal area A 4  at height zo. This gives the beam the same “footprint” in S 2  as it had in S 1 . Horizontal area A 5 , resulting from beam spread angle β 4  at bearing b 2 , is shown for comparison. 
       FIG.  84    shows illustrative fixture  8400 . Fixture  8400  may have one or more features in common with fixture  318 . Fixture  8400  may include lamina section  8402 . Lamina  8402  may include sections such as  8404 ,  8406  and  8408 . Segments  8404 ,  8406  and  8408  may be terminated by break-away joints  8410 ,  8412 ,  8414 ,  8416 ,  8418 ,  8420  and  8422 . Connectors  8424 ,  8426 ,  8428  and  8430  may be disposed on the lamina section between or adjacent the break-away joints. A user may separate sections and connectors at the break-away joints to provide a desired length of fixture  8400 . 
     Fixture  8400  may be connected with one or more of contacts  1414 ,  1604 ,  1608  and  1612  for transmission of electrical power. Fixture  8400  may be connected with one or more of contacts  1414 ,  1604 ,  1608  and  1612  for transmission of communications such as  510 . 
     Each section may include a first LED emitter string. Each section may include a second LED emitter string. Emitters in the first string may have a nominal first CCT. Emitters in the second string may have a nominal second CCT. The second CCT may be different from the first CCT. The user may instruct architecture  300  to mix the first CCT and the second CCT to provide illumination having a CCT that is between the first and second CCTs. 
     An emitter having the first CCT may be located adjacent an emitter having the second CCT. Emitter pair  8432  may include one emitter having the first CCT and one emitter having the second CCT. 
     Each string may include a current-regulating chip such as  8434  and a dissipative element such as  8436 . The dissipative element may include a resistor. 
     Lamina  8402  may be slidable into grooves such as  1044  and  1046  of fixture support  800 . 
       FIG.  85    shows fixture  8400  from a view different from that shown in  FIG.  84   . 
       FIG.  86    shows schematically illustrative circuit  8600 . Circuit  8600  may include string  8602 . Circuit  8600  may include string  8604 . Circuit  8600  may include power supply  8606 . Power supply  8606  may be controlled by device control module  8608 . 
     String  8602  may include high CCT LEDs  1 - 7  in series with current regulator Q 1  and resistor R 1 . String  8604  may include low CCT LEDs  8 - 14  in series with current regulator Q 2  and resistor R 2 . Table 39 lists illustrative string  8602  and string  8604  component IDs. 
     
       
         
           
               
             
               
                 TABLE 39 
               
             
            
               
                   
               
               
                 Illustrative string 8602 and string 8604 component IDs. 
               
               
                 Illustrative string 8602 and string 8604 components. 
               
            
           
           
               
               
               
               
            
               
                 String 8602 
                   
                 String 8604 
                   
               
               
                 Component 
                 Illustrative ID 
                 Component 
                 Illustrative ID 
               
               
                   
               
               
                 LED 1-7... 
                 2835W9N-F-Ra95- 
                 LED 8-14 
                 2835W6N-F-Ra95-2P 
               
               
                   
                 2P(D04-2HM) 5000 k 
                   
                 (H20-2HM) 2700K 
               
               
                 Q1 
                 IC PM2071 SOT23-6 RoHS 
                 Q2 
                 IC PM2071 SOT23-6 RoHS 
               
               
                 R1 
                 1/4W, 15R ± 1% (1206) 
                 R2 
                 1/4W, 15R ± 1% (1206) 
               
               
                 T 
                 Socket 
                 T 
                 Socket 
               
               
                   
                 Other suitable part IDs 
                   
                 Other suitable part IDs 
               
               
                   
               
            
           
         
       
     
     Input  8610  may be tied to a 24 VDC terminal of architecture  300 . 
     Power supply  8606  may provide pulse-width modulation (“PWM”), via a MOSFET in line  8612 , corresponding to Low VDC 1  (“L 1 ”) of string  8602 . Power supply  8606  may provide pulse-width modulation (“PWM”), via a MOSFET in line  8614 , corresponding to Low VDC 2  (“L 2 ”) of string  8604 . Power supply  8606  may provide separately controllable PWM to lines  8612  and  8614 . The power modulation may, for each line, reduce power output of the LEDs. By reducing power to one string relative to the other, a mixed CCT illumination may be achieved. Low end  8616  of power supply  8606  may a −24 VDC terminal of architecture  300 . 
     Device control module  8608  may correspond to a device control module such as  866 . 
     Each section of fixture  8600  may include a pair of strings such as  8602  and  8604 . Strings of different sections may run from a common high voltage rail to a common low voltage rail. 
       FIG.  87    shows schematically illustrative fixture  8700 . Fixture  8700  may include sections  8702 ,  8704 ,  8706 ,  8708  and  8710 . Each of the sections may be separable from the others by break-away joints. Each of the sections may include a high CCT (“HCCT”) string and a low CCT (“LCCT”) string. Each of the HCCT strings may have one or more features in common with string  8602 . Each of the LCCT strings may have one or more features in common with string  8604 . Sections  8702 ,  8704 ,  8706 ,  8708  and  8710  may include power modulation units  8712 ,  8714 ,  8716 ,  8718  and  8720 , respectively. Each of the power modulation units may have one or more features in common with power supply  8606 . Each of the sections may include a device control module (not shown) to control the corresponding power modulation unit. Each device control module may correspond to a device control module such as  866 . 
       FIG.  88    shows schematically illustrative fixture  8800 . Fixture  8800  may include sections  8802 ,  8804 ,  8806 ,  8808  and  8810 . Each of the sections may be separable from the others by break-away joints. Each of the sections may include a high CCT (“HCCT”) string and a low CCT (“LCCT”) string. Each of the HCCT strings may have one or more features in common with string  8602 . Each of the LCCT strings may have one or more features in common with string  8604 . All of sections  8802 ,  8804 ,  8806 ,  8808  and  8810  may modulated by power supply  8812 . Power supply  8812  may have one or more features in common with power supply  8606 . Power supply  8812  may provide pulse-width modulation (“PWM”), via a MOSFET in line  8814 , corresponding to the HCCT strings. Power supply  8812  may provide pulse-width modulation (“PWM”), via a MOSFET in line  8816 , corresponding to the LCCT strings. 
     Fixture  8800  may include a device control module (not shown) to control power supply  8606 . The device control module may correspond to a device control module such as  866 . 
       FIG.  89    shows illustrative printed circuit board composite layout  8900  for a fixture section based on high and low CCT LED strings such as  8602  and  8604 . A top layer of layout  8900  is shown in top layer view  8902 . A bottom layer of layout  8900  is shown in bottom layer view  8904 . View  8906  is a combination of top layer view  8902  and bottom layer view  8904 . Mounting locations for each of high CCT LEDs  1 - 7  are provided adjacent mounting locations for one of low CCT LEDs  8 - 14  in view  8906 . The high CCT LEDs are in series with current regulator Q 1  and resistor R 1  to form the high CCT string. The low CCT LEDs are in series with current regulator Q 2  and resistor R 2  to form the low CCT string. 
     The high CCT string runs from high voltage (“H”) power rail  8908  to low voltage (“L 1 ”) power rail  8910 . The low CCT string runs from high voltage (“H”) power rail  8908  to low voltage (“L 2 ”) power rail  8912 . 
     Connector interfaces  8914  and  8916  include mounting locations for continuity with each of high voltage (“H”) power rail  8908 , low voltage (“L 1 ”) power rail  8910  and low voltage (“L 2 ”) power rail  8912 . 
     Break-away joints  8918 ,  8920 ,  8922  and  8924  are provided. Because adjacent sections are arranged in parallel, a section that is powered via a connector may be separated from an adjacent section without loss of functionality. Multiple adjacent sections may be powered via a single connector. 
       FIG.  90    shows board  8906  with surface mounted female connector block  9002 . Block  9002  includes five rows,  9004 ,  9006 ,  9008 ,  9010  and  9012  of receptacles configured to receive a pin from a corresponding male connector block (not shown). Block  9002  may be mounted at connector interface  8914 . Thus, rows  9004  and  9012  may correspond to high voltage (“H”) power rail  8908 ; rows  9006  and  9010  may correspond to low voltage (“L 1 ”) power rail  8910 ; and row  9008  may correspond to low voltage (“L 2 ”) power rail  8912 . Axis L 10  is a central axis of block  9002  and is normal to face  9014  of board  8906 . The operational electrical potentials of the receptacles may be symmetrical under a 180 rotation about axis L 10 . Therefore, a male connector block configured to couple to female block  9002  can be coupled to in two orientations  180  apart without reversing polarity relative to female block  9002 . 
       FIG.  91    shows schematic layout  9100 . Layout  9100  may include fixture  9102 . Layout  9100  may include DC power supply  9104 . Layout  9100  may include power cable  9106  between power supply  9104  and fixture  9102 . 
     Fixture  9102  may include connector block  9108 . Connector block  9108  may include one or more features in common with connector block  9108 . 
     Power supply  9104  may be regulated to provide DC voltage V 1 . Fixture  9102  may operate at DC voltage V 2 . V 1  and V 2  may have a common ground. Fixture  9102  may include current-regulated strings such as  8602  and  8604  of circuit  8600 . Illustrative lengths L of cable  9106  between power supply  9104  and connector block  9108  are set forth above. For any of the lengths, V 2  may be no less than 85% V 1 , despite any line loss that may be caused by cable  9106 , and without any voltage boost between power supply  9104  and connector block  9108 . 
       FIGS.  92 - 98    show illustrative driving element  9201 , fixture support  9202 , LED modules  9203 , and module pressing buckles  9304 . Driving element  9201  may have one or more features in common with circuit  8600 . Fixture support  9202  may have one or more features in common with fixture support  800 . LED modules  9203  may have one or more features in common with section  8404 . Fixture support  9202  may include mounting slot  9505 . An end of fixture support  9202  may be engaged by power inlet  9206 . An end of fixture support  9202  may be engaged by tail cover  9307 . Driving element  9201  and LED modules  9203  may be disposed in mounting slot  9505 . Module pressing buckles  9304  may be disposed in mounting slot  9505 . Module pressing buckles  9304  may press and limit LED modules  9203 . Power inlet  9206  may be in electrical communication with driving element  9201 . Driving element  9201  may be in electrical communication with LED modules  9203 . When assembled, driving element  9201  and LED modules  9203  may be disposed in mounting slot  9505 , and power inlet  9206  and tail cover  9307  may be disposed at the head and tail ends of fixture support  9202 . Power inlet  9206  and tail cover  9307  may block the ends of fixture support  9202 . Power inlet  9206  may be in electrical communication with driving element  9201  to effect power supply connection. LED modules  9203  may be press-fitted into mounting slot  9505  using module pressing buckles  9304 . Module pressing buckles  9304  may be lodged in mounting slot  9505  such that they stably press LED modules  9203  to prevent LED modules  9203  from loosening. 
     LED module  9203  may include cut-off hole groups  9408 . Cut-off hole groups  9408  may be distributed at equal intervals along the length of LED module  9203 . Each cut-off hole group  9408  may include several cut-off holes. Cut-off hole groups  9408  may be arranged for conveniently severing LED modules  9203 . A user may cut LED module  9203  by scissors to adjust the length of an LED module  9203  LED modules  9203  may thus be installed in fixture supports  9202  of different lengths. 
     A side of driving element  9201  may include driving buckle position  9509 . Driving buckle position  9509  may abut an inner wall of mounting slot  9505 . Driving element  9201  may be press-fitted in mounting slot  9505 . Driving buckle positions  9509  may abut, and may be fastened to, an inner wall of mounting slot  9505 . 
     Module pressing buckle  9304  may include pressing element  9610 . Sides of pressing element  9610  may be provided with pressing buckle positions  9611 . Pressing buckle positions  9611  may abut inner wall of mounting slot  9505 . A lower end surface of pressing element  9610  may abut the surface of the LED module  9203 . When module pressing buckle  9304  is mounted, it may be put into mounting slot  9505  from the upper end of fixture support  9202 ; module pressing buckle  9304  may be placed diagonally at a middle position of two light sources on LED module  9203  at an angle of 59°; and module pressing buckle  9304  may be pressed by hands and rotated 59° (e.g., clockwise) to be perpendicular to the side wall of the fixture support. This may facilitate the pressing buckle positions  9611  to be buckled into the inner wall of the mounting slot  9505 . 
     Lower end surface of pressing element  9610  may be a horizontal surface. Lower end surface of pressing element  9610  may be a horizontal smooth surface. This may reduce or avoid wear of LED module  9203  when module pressing buckle  9304  presses LED module  9203 . 
     Driving element  9201  may be provided with first electrical connector  9312  at an end close to power inlet  9206 . First electrical connector  9312  may be electrically connected to power inlet  9206 . First electrical connector  9312  may be electrically connected to power inlet  9206  via a first conductive pin  9315  or a wire. First conductive pin  9315  may be directly plugged in. The wire may be suitable for connection over a longer distance. 
     Driving element  9201  may include second electrical connector  9313  at an end away from the power inlet  9206 . LED module  9203  may include provided third electrical connectors  9314 . Second electrical connector  9313  may be electrically connected to third electrical connector  9314 . Second electrical connector  9313  may be electrically connected to third electrical connector  9314  via a second conductive pin  9316  or a wire. Second conductive pin  9316  may be directly plugged in. The wire may be suitable for connection over a longer distance. 
     Two adjacent LED modules  9203  may be connected via a conductive pin or wire. 
     Upper end surface of fixture support  9202  may include a clamping slot  9517  and opening  9218 . Opening  9218  may be in communication with clamping slot  9517 . The lamp may include light-transmitting cover  9319 . Sides of a lower end surface of light-transmitting cover  9319  may be provided with clamping sheets  9820 . Clamping sheets  9820  may be arranged in clamping slot  9517 . Light-transmitting cover  9319  may be used to cover opening  9218 . Opening  9218  may be in communication with mounting slot  9505 . This may facilitate installation of LED module  9203  and the driving element  9201 . Light-emitting cover  9819  may protect the LED module  9203 . 
     The lamp may include a hanging member such as  9221 . Hanging member  9221  may be respectively disposed on ends of the upper end surface of fixture support  9202 . Hanging member  9221  may be used to hoist or suspend fixture support  9202 . 
     All ranges and parameters disclosed herein shall be understood to encompass any and all subranges subsumed therein, every number between the endpoints, and the endpoints. For example, a stated range of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more (e.g. 1 to 6.1), and ending with a maximum value of 10 or less (e.g., 2.3 to 9.4, 3 to 8, 4 to 7), and finally to each number 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 contained within the range. 
     Thus, apparatus and methods for fixtures, power and control of same have been provided. Persons skilled in the art will appreciate that the present invention can be practiced by other than the described examples, which are presented for purposes of illustration rather than of limitation. The present invention is limited only by the claims that follow.