Abstract:
A power system for an aircraft is disclosed. The power system comprises a power module unit and at least one mounting rail detachably coupled to the power module unit. The mounting rail provides structural support and electrical power to the power module unit. A power system in one embodiment may use mounting rails that double as power rails supplying power to the power module unit. Control is accomplished over a wireless link. The power rail control may be accomplished remotely via a standard or solid state relay. Normal rail power for the rail mounted power module unit may come from the utility bus.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to an aircraft and more specifically to a power system for accessories in the aircraft.  
       BACKGROUND OF THE INVENTION  
       [0002]     In today&#39;s commercial airplanes, a power system for accessories such as laptop or notebook computer has complex power, delivery and discrete wiring, and is difficult to install. When a power system unit needs to be moved or replaced, it can take several minutes to accomplish the job based upon the complexity of the system. When this move or replace is associated with a seat repitch or retrofit within the aircraft, a great deal of time can be lost. Accordingly, it is desired to provide for the installation and removal of power system for accessories without the difficulties and time loss associated with the conventional overhead video passenger service.  
         [0003]     Accordingly, what is needed is a system and method for providing a simple, lightweight and reliable power system unit in an aircraft. The present invention addresses such a need.  
       SUMMARY OF THE INVENTION  
       [0004]     A power system for an aircraft is disclosed. The power system comprises a power module unit and at least one mounting rail detachably coupled to the power module unit. The mounting rail provides structural support and electrical power to the power module unit.  
         [0005]     A power system in one embodiment may use mounting rails that double as power rails supplying power to the power module unit. Control is accomplished over a wireless link. The power rail control may be accomplished remotely via a standard or solid state relay. Normal rail power for the rail mounted power module unit may come from the utility bus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  illustrates a schematic diagram of a cabin services system in accordance with a number of embodiments.  
         [0007]      FIG. 2A  illustrates a block diagram of a cabin services system in accordance with one of the embodiments.  
         [0008]      FIG. 2B  illustrates a block diagram of an alternate embodiment of a cabin services system in accordance with one of the embodiments.  
         [0009]      FIG. 2C  illustrates one implementation of the cabin attendant panel.  
         [0010]      FIG. 3  is a diagram that illustrates the operation of passenger service unit mounting rails with circuits connected thereto.  
         [0011]      FIG. 4  is an example of a simplified wireless overhead electronics unit.  
         [0012]      FIG. 5  is a perspective view of a portion of a passenger service unit module.  
         [0013]      FIG. 6A  is a view of an embodiment of a power system.  
         [0014]      FIG. 6B  is a block diagram of one embodiment of a power module unit.  
         [0015]      FIG. 6C  is a block diagram of another embodiment of a power module unit.  
         [0016]      FIG. 7A  is a detailed view of the power module unit of  FIG. 6B .  
         [0017]      FIG. 7B  is a detailed view of the power module of  FIG. 6C .  
         [0018]      FIG. 8  is a block diagram of the embodiment of a power switching system for use with the power module unit. 
     
    
     DETAILED DESCRIPTION  
       [0019]     The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein.  
         [0020]     A method and system in accordance with a number of embodiments streamlines the process for installation and removal of a one or more power module units over conventional power module units. These embodiments may be utilized in conjunction with a rail system within an aircraft for providing power to the power module unit. In so doing, a system is provided that may allow for a power module unit to be easily installed and removed. U.S. patent Ser. No. 3688P entitled “Simplified Power System for a Cabin Services System for an Aircraft”, filed on Dec. 16, 2005 and assigned to the assignee of the present application, describes a powered rail system in accordance with a number of embodiments and is incorporated by reference in its entirety herein. The embodiment of the power module unit is described in the context of a cabin services unit; however, one of ordinary skill in the art readily recognizes a variety of cabin services units could be utilized with a power module unit and they would be within the spirit and scope of the present invention. Therefore the following description is utilized to describe with particularity the features of the described embodiment, but is in no way limited by the embodiments.  
         [0021]     A cabin services system  100  according to a number of embodiments is illustrated in  FIG. 1 . The cabin services system  100  may include a plurality of wireless networks  102 . Each of the wireless networks  102  may transmit and receive passenger services commands. Each of the wireless networks  102  may be preferably associated with a seat group. The cabin services system  100  may further include wireless passenger control units  202   a - 202   n , passenger service units  204   a - 204   n , a plurality of cabin zone units  114 , a cabin control unit (not shown) and a cabin attendant panel  112 . Each passenger control unit  202   a - 202   n  may transmit cabin services system commands to a corresponding passenger service unit  204   a - 204   n . Each passenger service unit  204   a - 204   n  may include a wireless receiver (not shown) and a controller (not shown) which are used to control passenger service unit functionality. The cabin services system  100  may further include a passenger service unit power rail (not shown) which is integrated with a passenger service unit mounting rail (not shown) to provide electrical power to each passenger service unit  204   a - 204   n . Finally, individual personal air outlet fans may be installed in each passenger service unit  204   a - 204   n  to eliminate flex hose hookups that are typically required in conventional cabin services systems.  
         [0022]     Additionally, systems may be greatly simplified, passenger controls may be more easily reached by passengers, and each passenger service unit  204   a - 204   n  may be quickly installed and maintained without any wiring or duct hookups.  
         [0023]     Similarly, wireless interfaces may be used to provide data or control of other passenger service unit module functions. For example, video monitors mounted onto a passenger service unit may receive video data wirelessly via a cabin wireless network. Also, passenger signage can be controlled (turned on/off or fed content for display) via a wireless interface.  
         [0024]     Taken together, these wireless interfaces allow for the elimination of wiring to passenger service unit modules. This leaves electrical power as the electrical interface to each passenger service unit module via the passenger service unit mounting rails themselves and also provides a means for powering non-essential or essential loads on these rails. In one implementation, the passenger service unit mounting rails are energized with electricity such that when a passenger service unit module is clipped to the mounting rail, electrical contact is also made between the passenger service unit module and the mounting rail to provide electrical energy to the passenger service unit module.  
         [0025]     The powered passenger service unit rail system is comprised of the following components:  
         [0000]     Airplane Wiring  
         [0026]     Airplane wiring may consist of four wires:  
         [0027]     Two non-essential power wires (typically 115 VAC and current return)  
         [0028]     Two essential power wires (typically 28 VDC and current return)  
         [0000]     Stow Bin Assembly  
         [0029]     A typical commercial stow bin assembly consists of a housing assembly that supports a stow bin, passenger service unit mounting rails and other equipment.  
         [0000]     Simplified Overhead Electronics Unit (SOEU)  
         [0030]     The simplified overhead electronics unit (SOEU) for the embodiment performs three functions: 
        Convert power inputs into a “safe-to-touch” power output (such as 12V DC)     Switch the outputs from being powered by the non-essential power input to being powered by the essential power input whenever the essential bus becomes live     Reversing the polarity of the outputs when the essential bus becomes live        
 
         [0034]     Note that the simplified overhead electronics unit must perform its functions while maintaining circuit separation between the non-essential and the essential busses at all times.  
         [0035]     To describe the features of the present embodiment in more detail refer now to the following description in conjunction with the accompanying figures.  
         [0000]     Cabin Services System (CSS)  
         [0036]     In one embodiment, a cabin services system  100 ′ may include a cabin control unit  113  wired to a cabin attendant panel  112 ′ as shown in  FIG. 2A . The cabin control unit  113  may be wired to a plurality of cabin zone units  114 . The cabin zone units  113  may in turn communicate wirelessly to a plurality of wireless seat group networks  115 . Each wireless seat group network  200  may include a plurality of passenger control units  202   a - 202   n  that communicate wirelessly with one passenger service unit  204 . In this method, data from the cabin attendant panel  112 ′ may be relayed by wiring to the cabin zone unit  114 ′ data and may be transmitted by the cabin zone unit  114 ′ wirelessly to the passenger service unit  204 . The wiring from the cabin attendant panel  112 ′ to cabin zone unit  114 ′ may exist for functions other than passenger service functions, (such as general cabin lighting control, cabin air temperature data, zonal attendant call light control and many other functions not related to the passenger service functions) thereby eliminating the need to add extra wire or wireless radio hardware for the cabin attendant panel  112 ′ to passenger service unit  204 ′ communication.  
         [0037]      FIG. 2B  illustrates a block diagram of an alternate embodiment of a cabin services system  100 ″. The cabin services system  100 ″ may include a wireless cabin attendant panel  112 ″ that may communicate wirelessly with a plurality of wireless seat group networks. A wireless seat group network  200  may include a plurality of passenger control units  202 ′ a - 202 ′ n  that may communicate wirelessly with a passenger service unit  204 ′. This method may allow small commercial aircraft to perform cabin services functions normally found on large commercial aircraft. Further, the wireless cabin attendant panel  112 ″ may wirelessly transmit commands to a plurality of other airplane components in order to control functions such as general cabin lighting, zonal attendant call light, and record cabin air temperature data. Each of the components listed above may be wirelessly enabled to afford this functionality.  
         [0000]     Passenger Service Unit (PSU)  204   
         [0038]     The passenger service unit  204  may comprise a wireless receiver  206 , a controller  208 , memory  210 , reading lights  212   a - 212   n , a flight attendant call light  214 , a flight attendant call cancellation switch  216 , personal air outlets  218   a - 218   n , and a reed switch  220 . The features of each of these components are described in more detail in conjunction with the accompanying figures hereunder.  
         [0039]     The wireless passenger control unit transmitter  202  may allow for communication with the passenger service unit  204  without an in-flight entertainment system or any other wires. Thus, the cabin services system is not reliant on an in-flight entertainment system and an aircraft can be built without a conventional in-flight entertainment system. This allows airlines to choose not to install wired in-flight entertainment systems (which significantly reduces weight) or to use the latest portable in-flight entertainment systems, such as the digEplayer or eXpress, on widebody aircraft.  
         [0040]     A passenger control unit including the wireless passenger control unit transmitter  202  may be installed anywhere in the passenger seat (seat arm, seat back, etc.) within easy reach of the passenger. Wireless passenger control unit transmitters  202  may be battery powered, or may use energy harvesting for power without batteries. An energy harvesting wireless passenger control unit transmitter may be constructed, for example, by integrating an EnOcean piezoelectric or electrodynamic wireless transmitter (www.enocean.com, part numbers PTM100 or PTM200) into a passenger control unit such that passenger actuation of the passenger control unit control buttons closes a specific control switch on the EnOcean transmitter and depresses the energy bar, thus resulting in wireless transmission of command telegrams from the passenger control unit to a receiver (for example, an EnOcean receiver—EnOcean P/N RCM 120) mounted in the passenger service unit. The command telegrams may include an identifier unique to the transmitter and indication of which control switch was closed at the time of pressing the energy bar.  
         [0000]     Passenger Service Unit (PSU) Functionality  
         [0041]     Passenger service unit modules may come in many forms. Any given passenger service unit module may include one or more of the following functionalities: 
        Flight attendant call light     Reading light     Personal air outlets     Emergency oxygen     In-flight entertainment system control such as video or audio channel selection     Cabin signage such as “fasten seat belt”, “no smoking” or other passenger information        
 
         [0048]     It should be understood by one of ordinary skill in the art that a variety of other functions could be included and their use would be within the spirit and scope of the present embodiment.  
         [0049]     In one embodiment, each passenger service unit may utilize the following features to allow it to easily snap onto a mounting rail in an aircraft without wire, duct or tube hookups: a 12V DC powered mounting rail, wireless technology, and fans mounted onto a passenger service unit.  
         [0050]     Powered mounting rail: the passenger service unit mounting rail provides both a structural interface for installing a passenger service unit as well as an electrical power interface. Each passenger service unit may simply snap onto the mounting rail for both mechanical attachment and for electrical power.  
         [0051]     Wireless technology: together, the wireless passenger control unit, wireless interface to the cabin attendant panel and the passenger service unit power rail (or power line) within the mounting rail may eliminate the need to hook up wires to a passenger service unit.  
         [0052]     Fans mounted onto a passenger service unit: ducting for a personal air outlet and hookup to each passenger service unit may be replaced by individual personal air outlet fans built into each passenger service unit. This results in less noise (compared to high pressure ducting and nozzles of a conventional personal air outlet).  
         [0053]     The reading light, flight attendant call, nozzles and fans of a personal air outlet and emergency oxygen may be assembled in an integrated passenger service unit module that snaps onto the mounting rail without any wire or duct hookups.  
         [0054]     In one implementation, fans (mounted onto a passenger service unit) may draw “fresh” air into a passenger service unit plenum through an inlet grill located adjacent to the cabin air distribution nozzles. In such an implementation, ducts of a personal air outlet may be eliminated and cabin noise may be reduced.  
         [0055]     In one implementation, oxygen masks may be deployed by turning off power to a utility bus on the passenger service unit mounting rail and momentarily turning on an essential power bus and reversing electrical polarity on a power rail within the passenger service unit mounting rail. Current will then flow through a diode in the oxygen circuit to activate the mask drop solenoid.  
         [0000]     Cabin Attendant Panel (CAP)  
         [0056]      FIG. 2C  illustrates one implementation of the cabin attendant panel  112 . The wireless cabin attendant panel  112  may be used to transmit wireless control signals via control button  402  directly to groups of passenger service units for functions such as turning on/off passenger signage (e.g., “No Smoking”, “Fasten Seat Belt”, etc.), and for resetting the passenger service units via reset button  404  during gate turnaround between flights (e.g., turning off all reading lights, personal air outlets, and flight attendant call lights; and turning on all “No Smoking” and “Fasten Seat Belt” signs). In this manner, the cabin control unit and cabin zone module may be bypassed, greatly simplifying the system architecture.  
         [0057]     In a preferred implementation of the cabin attendant panel, the cabin attendant panel may make use of other aircraft wireless transmitters located in various positions in the airplane to relay its control signals to the seat group networks. These other wireless transmitters can include a wireless function added to the cabin zone modules (part of the cabin services system). In this case, the cabin attendant panel may be part of a wired or wireless network common to these zone control electronic boxes. It may also be part of other aircraft systems, such as a wireless cabin network. The cabin attendant panel can further include a display (not shown) for displaying data (e.g., prognostic data) to a mechanic or flight personnel, as described in greater detail below.  
         [0000]     Passenger Service Unit (PSU) Mounting Rails  
         [0058]      FIG. 3  is a diagram that illustrates the operation of the passenger service unit mounting rails with passenger service unit circuits as indicated by loads  403   a ,  403   b  and  403   c  connected thereto. As is seen, under normal operating conditions, a diode  402  in series with each passenger service unit module circuit allows current to flow through non-essential circuits  408 . Non-essential circuits are, for example, circuits for in-flight entertainment monitors, reading lights and flight attendant call lights. For essential circuits  410 , such as one for oxygen deployment, a diode  404  in series prevents current from flowing into the circuit. Thus, under non-normal operating conditions, such as during emergency oxygen deployment, the output of the wireless? overhead electronics unit  406  reverts from a non-essential power mode to an essential power mode and the output polarity is reversed. Thus, the diodes  402  on the non-essential circuits prevent current to flow through them while the diodes  404  on the essential circuits now allow current to flow through them. This can be used, for example, to momentarily power a solenoid that opens an oxygen mask door thus allowing oxygen masks to fall into the cabin, or, for example, to continuously power a wirelessly activated oxygen system.  
         [0059]     Note that if a circuit  412  requires power during both normal and non-normal conditions, diodes may be used to provide power to the circuit  412  under either condition. Also note that if the circuit  412  could operate with either polarity, no diodes would be necessary and the circuit may be connected to each of the rails.  
         [0060]     In one implementation, the 12V DC mounting rail contact and the current return contact may be widely spaced. In this implementation, such a design helps to prevent accidental shorting across the contacts with, e.g., a conductive tool that might otherwise startle a mechanic by discharging sparks. Additionally, all portions of the passenger service unit mounting rails that cannot be contacted by the electrical contact of the passenger service unit may be made from non-conductive materials or finished with non-conductive finishes as another preventive measure against accidental shorting.  
         [0061]     The passenger service unit power rail may implement any low voltage power type, AC or DC. Many power rail designs other than that shown in  FIG. 3  are feasible. For example, the male spring contact may be moved to the passenger service unit with the female contact inserted into a groove in the mounting rail arm. In this case, both the 12V DC and return rails may be located on the same side of the passenger service unit (instead of opposite sides) since both mounting rail contacts can be recessed protecting them from accidental shorting with, e.g., a conductive tool.  
         [0062]      FIG. 4  is an embodiment of a simplified overhead electronics unit (SOEU)  400 . As is seen, a power panel  402  provides power to the simplified overhead electronics unit  406  via a non-essential power bus  404  and/or an essential power bus  406 . In this embodiment the non-essential power bus  404  may be 115 VAC and the essential power bus  406  may be 28 VDC. The simplified overhead electronics unit  400  may include a first converter  408  for converting the essential voltage from in this embodiment 28 VDC to 12 VDC and a second converter  410  for converting the essential voltage bus from 115 VAC to 12 VDC. The simplified overhead electronics unit  406  may be typically mounted on the stow bin assembly. In this example, only power from the non-essential power bus inputs are being used to create the 12 VDC output under normal operating conditions (when the essential bus  406  is not live). When the essential power bus  406  becomes live, a relay may be energized to switch the output from being driven by the non-essential power bus  404  to being driven by the essential power bus  406  input. Note that the output polarity will be reversed relative to the normal operating condition when this occurs.  
         [0063]     In this example:  
         [0064]     The non-essential power bus  404  may be 115 VAC and may be transformed to 12 VDC by an AC-to-DC converter  610  within the simplified overhead electronics unit  400 .  
         [0065]     The non-essential power bus  404  may also be turned off without turning on the essential power bus  406  by opening a circuit breaker or relay, typically located in a power panel.  
         [0066]     The essential power bus  406  may be 28 VDC and may be converted to 12 VDC by a DC-to-DC converter  608  within the simplified overhead electronics unit  400 .  
         [0067]     The essential power bus  406  may typically be turned on via a relay typically located in a power panel. The relay may, for example, be activated by a switch  412  in the Flight Deck, such as for emergency oxygen deployment.  
         [0068]     The power buses may be fed through the simplified overhead electronics unit  406  for installation convenience. This may allow several simplified overhead electronic units  400  to be daisy chained together down the airplane.  
         [0069]     There are several ways to accomplish the simplified overhead electronics unit  400  functionality. The example circuit shown in  FIG. 4  is just one way to implement this function.  
         [0000]     Passenger Service Unit Mounting Rail  
         [0070]      FIG. 5  is a perspective view of a portion of the passenger service unit module  300 . The portion of the passenger service unit module  300  illustrated in  FIG. 5  shows an electrical contact assembly  301 . The assembly  301  may comprise an electrical spring contact  302  and a plastic, non-conductive, insulating support  304 . The electrical spring contact  302  may be made of, for example, beryllium copper that is nickel and gold plated. The electrical spring contact  302  may be designed to clip onto the round portion of electrically conductive passenger service unit mounting rail  306 . The plastic support  304  may be also designed to clip onto the passenger service unit mounting rail  306  and may be intended to support the electrical spring contact  302  and to prevent the electrical spring contact  302  from rocking back and forth on the passenger service unit mounting rail  306 . The electrical contact assembly  301  may be loosely fastened to a passenger service unit module such that when a passenger service unit module vibrates under the passenger service unit mounting rail  306 , the electrical spring contact  302  will float over the passenger service unit module and maintain its grip on the passenger service unit mounting rail  306 . With these elements in place, the electrical spring contact  302  may mate with the electrically conductive portion of the passenger service unit mounting rail  306  when the passenger service unit is installed and held in place by the passenger service unit catches (not shown).  
         [0071]     Accordingly, each passenger service unit module  300  may receive electrical power from the mounting rail  306  via its electrical spring contacts  302 .  
         [0072]     Passenger service unit mounting rails may be typically constructed from an aluminum extrusion that is approximately the same length as the stow bin assembly. In this embodiment the mounting rails may have the following features:  
         [0073]     Each rail may be electrically connected to one of the outputs from the simplified overhead electronics unit  406  via a wire. Thus, one rail may be connected to the normally positive DC output and the other rail may be connected to the normally negative DC output.  
         [0074]     The edge of the rail that passenger service unit module clips may attach to is kept electrically conductive. While most surfaces of the rail are typically primed and painted, the aluminum rail along this edge may be plated, for example, with nickel and gold to provide electrical conduction.  
         [0075]     Note that the simplified overhead electronics unit above may energize these rails with 12 VDC voltage.  
         [0076]     In a system and method in accordance with the present embodiment the passenger service unit mounting rails may perform two functions:  
         [0077]     (1) Mechanical support of the passenger service unit modules; and  
         [0078]     (2) Electrical supply to the passenger service unit modules.  
         [0079]     This may minimize the addition of new components or weight to the airplane. However, because of this dual functionality, electrical isolation may be required between the rail and any adjacent conductive airplane parts. Thus, plastic bushings may likely be used at the rail mounting points.  
         [0080]     When combined with a wireless data infrastructure, the mounting rails may greatly simplifies the passenger service unit installation by providing electrical power to passenger service unit modules via the passenger service unit mounting rails instead of through electrical wiring. With no data or power wiring interfaces, passenger service unit modules may be able to be installed, removed or relocated much more rapidly.  
         [0000]     Power Module Units  
         [0081]      FIG. 6A  is a view of one embodiment of a power system  600 . In this system, a power panel may be mounted on structural bin rails that double as power rails  601 . The rails  601  provide power to the power module unit  604 . Current limiting and short circuit protection may be provided by a power module unit power supply.  
         [0082]      FIG. 6B  is a block diagram of one embodiment of a power module unit  602 .  FIG. 7A  is a detailed view of the power module unit  602  shown in  FIG. 6B .  
         [0083]     Referring to  FIG. 7A , power supply  606   a  may provide power conditioning to the three power outlets  608   a - c  limiting the current sourced to each outlet to a predetermined current such as 1.5 A. In this embodiment, the three power outlets may provide 12 VDC.  
         [0084]      FIG. 6C  is a block diagram of another embodiment of a power module unit  604 .  FIG. 7B  is a detailed view of the power module  604 .  
         [0085]     Referring to  FIG. 7B , the power supply  606   b  may provide power to a power outlets  610  limiting the current source to a predetermined current such as 1.5 A. In this embodiment, the power supply may provide power conditioning and 60 HZ power inversion to provide a standard 115 VAC power outlet.  
         [0086]     In both  FIGS. 7A and 7B , the passenger service unit power supply may obtain their power from the powered rails. That power is then conditioned by the passenger service unit power supply  606   a  and  606   b  and distributed to the individual automotive or defined power connectors. Accordingly, the power supply may provide power to an accessory portable device on the aircraft such as a laptop computer, notebook computer, personal digital assistant, portable phone, MP3 player, IPOD or the like.  
         [0087]      FIG. 8  is a block diagram of the embodiment of a power switching system  800  for use with a power module unit  802  in accordance with a number of embodiments. The power switching system  800  may utilize a relay  808  (either a mechanical or a solid state). Since the power module unit  802  may share the power rails  306   a - 306   b  with the oxygen passenger service unit (not shown), each power module unit  802  may be protected by diode  812  to prevent power from being applied to the power system  802  while oxygen may be deployed.  
         [0088]     In this system, the power rails  306   a - 306   b  may also double as the oxygen mask deploy wiring. The oxygen deploy discrete output  804  may be tied to the relay coil  808 . When oxygen is commanded, the relay  808  may be energized and 12 VDC power from the primary bus may be routed to the power rails  306   a - 306   b  in reverse polarity causing the oxygen passenger service unit door solenoid  806  to be energized causing the oxygen masks (not shown) to deploy. The diode  812  in the power module unit  802  may keep the power system off until utility bus power is restored and the oxygen discrete is returned to its normal state. The details of one embodiment of an oxygen deployment system are described, for example, in U.S. patent Ser. No. 3688 entitled “Simplified Power System for a Cabin Services System for an Aircraft”, filed on Dec. 16, 2005, assigned to the assignee of the present embodiment, and incorporated by reference herein.  
       Other Embodiments  
       [0089]     Many other embodiments of this system are possible:  
         [0090]     In addition, separate power rails may be added to the stowage bin assembly, parallel to the passenger service unit mounting rails, in order to provide the electrical power function.  
         [0091]     This system does not rely on wireless data communication to the passenger service unit modules. Other communication options may include traditional wires or communications over power line (COPL) technologies.  
         [0092]     Circuits that need to operate when power is completely shut off from the rails may include a battery or capacitor that is charged via the rails during normal operation.  
         [0093]     The power rail may use any of low voltage power type, AC or DC. Many power rail and electrical contact designs other than that shown in  FIG. 5  are feasible.  
         [0094]     Accordingly, a system and method in accordance with the embodiment provides an overhead video system that is integrated with a passenger service unit power rail to provide a modular system. As a result, the overhead system can be installed and replaced in an efficient fashion.  
         [0095]     Although the present embodiment has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present embodiment. For example, implementations of a cabin services system described above can be implemented in any type of commercial vehicles including, e.g., helicopters, passenger ships, automobiles, and so on. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.