Abstract:
An apparatus for indicating the configuration of a cable television line amplifier. The line amplifier contains a controller that senses a preset voltage on a status indication line. When the amplifier is reconfigured, such as by adding new circuits containing new functions or features, these new circuits contain resisters that are shunted to modify the preset voltage level on the appropriate status indication line. The controller senses the modified voltages and provides an indication of the new function of the new circuit to a headend through a cable television distribution system.

Description:
This application claims the benefit of 60/019,007 filed Jun. 3, 1996. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an apparatus for sensing the configuration of a cable television line amplifier and more particularly to an apparatus that detects different modules plugged into a line amplifier, and transmits the configuration of the modules to a headend controller. 
     Line amplifiers are commonly used in cable television distribution systems to extend the range that television signals are transmitted. Line amplifiers contain different modules that have a variety of functions. The functions include automatic gain control (AGC) control, monitoring, reverse path amplification and multiple amplified output ports. With present cable TV distribution systems, the system operator must rely on installation notes from a technician when configuring his line amplifiers. The technician uses the notes to configure the line amplifier by setting jumpers on a module in the line amplifier or by entering data in the memory of the module. Inaccurate notes could result in lost time to set up the line amplifier station. Incorrect entry of the data into the module could result in faulty operation of the amplifier. 
     SUMMARY OF THE INVENTION 
     The invention permits a status monitoring module within a line amplifier to be automatically configured upon installation without the technician having to enter data or set jumpers within the module, regardless of the number of module types that are installed. The invention will also allow amplifier configuration changes in the field to be completed electronically and instantaneously without the technician having to change the module switch settings or without requiring the re-entering of data in the module. The status monitor utilizes A/D inputs to read DC voltages supplied by the various modules. These voltages represent the amplifier&#39;s configuration. In response to different modules being added to the line amplifier, these voltages would automatically change upon the addition of a module with a new option. A controller within the line amplifier would then read the voltage change and send a signal either over the distribution system to a headend or locally to a test point on the line amplifier indicating a change in the amplifier&#39;s configuration. 
     The foregoing and other objects of the present invention a well as the invention itself, may be more fully understood from the following description when read in conjunction with the accompanying drawings. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIG. 1 is a simplified block diagram of a line amplifier implementing the invention; and 
     FIG. 2 is a simplified block diagram of the status monitoring device shown in FIG.  1  and incorporating the features of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, there is shown a dual line amplifier  10  having an input port  14  coupled through cable  11  to a headend controller  12 . Amplifier  10  has output ports  21  and  22  coupled to subscribers  16 . Amplifier  10  includes amplification circuitry  20 , monitoring circuitry  24  and a removable module containing reverse path circuitry  26 . Amplification circuitry  20  amplifies the signal on port  14  before feeding it to output ports  21  and  22 . Circuitry  24  contains an RF detect circuit  50 , status monitor circuitry  30 , indicator circuitry  64  and a modularized and removable AGC control circuit  52 . Monitoring circuitry  24  determines the configuration of line amplifier circuitry  20 , stores this configuration and feeds a signal indicative of the configuration through reverse path circuitry  26  to headend controller  12 . Monitoring circuitry  24  internally generates one or more preset signals having a voltage level references. These signals are fed to status monitor circuit  30 . The voltage level references of these signals change when the amplifier  10  is reconfigured, thereby providing an indication to status monitor circuit  30  of the current state of the amplifier configuration. 
     Amplifier  10  receives an RF signal on input port  14  that is fed through high/low filter  18 , equalizer  32 , and amplified by amplification stage  34 . The output of the amplification stage  34  is fed through variable loss inserter  36 , or attenuator, and directed through coupler  38  to output amplifiers  42  and  44 . The output of amplifiers  42  and  44  are fed through filters  46  and  48 , respectively, to output terminals  21  and  22 . The outputs of amplifiers  42  and  44  are also fed to monitoring circuitry  24 . 
     Monitoring circuitry  24  contains an RF detector  50  that receives the output signals of amplifiers  42  and  44 . The RF detector  50  then feeds the received signal to status monitor circuit  30  and AGC control circuitry  52 . As a result of the signal being received from RF detector  50 , AGC control circuit  52  adjusts the attenuation of inserter  36 , to vary the gain of amplification circuitry  20 . 
     Status monitor circuit  30  receives on line  61  a DC signal having a first reference voltage level. The first voltage level is generated by pull down resistor  58 , physically disposed on reverse path circuit  26 , and pull up/pull down resistor network  63  disposed on monitoring circuitry  24 . Status monitor circuit  30  receives through auto amplifier detect line  67  a DC signal having a second voltage level. The second voltage level is generated by pull up/pull down indicator circuit  64  that is also disposed on monitoring circuit  24 . If removable AGC control circuitry  52  is not installed, status monitor circuit  30  is fed a DC signal having a third voltage level on AGC mode line  77 . The third voltage level is generated by a pull-up resistor  79 . If AGC control circuit  52  is installed, status monitor circuit  30  is fed on line  77  a DC signal having a voltage level set by pull down resistor  62 , which is shunted to ground. 
     Reverse path circuit  26  includes a coupler  66 , which receives the reverse path RF signal from filters  46  and  48  and feeds the RF signal through reverse amplifier  68  through reverse filter  49  to headend controller  12 . Status monitor circuit  30  feeds a status signal containing an indication of the signals on lines  67 ,  77 , and  61  as well as an indication of the detected output-configuration of amplifier  10 . This status signal is fed through reverse amplifier  68  and reverse path filter  49  to the headend controller  12 . 
     Resistors Rv and Rg represent resistors on the motherboard of amplifier  10 . Rg is preferably a fixed preset value, and the value of Rv is preferably set as a function of the number of amplifier outputs (i.e., a single, a dual, or a triple output). Resistor  62  is disposed within removable AGC control circuit  52 . AGC control circuit  52  may be added to the amplifier  10  either during the amplifier production or after the amplifier  10  has been installed in the field. 
     Referring to FIG. 2, there is shown the status monitoring circuit  30 , having a controller  70  that reads the DC signals from the AGC control circuit  52  through analog-to-digital (A/D) converter  72  and the DC signal from the first reference voltage level  64  through A/D converter  74 . Controller  70  reads the DC signal on line  67  through A/D converter  71 . Controller  70  is connected to a test interface  76 , where the controller  70  sends and receives signals to the test interface  76  to permit a technician to connect test equipment thereto that indicates the AGC control circuit  52  and indicator circuit  64  configuration. Controller  70  uses A/D converter  80  to read values from the RF detector  50 , and to read and store the value of the signal from A/D connector  80  and detected RF values into RAM memory  78 . 
     In other alternate embodiments of the invention (not shown), modules having circuits (other than reverse path circuit  26 ) may be connected into the line amplifier  10 , and the configuration and function of these modules may be detected using an auto module type detect circuit. Referring to FIG. 1, the auto module type detect circuit  75  includes A/D converter  74 , line  61 , and circuit  63 . The auto module type detect circuit  75  monitors the type of module (i.e., distribution reverse amplifier or fiber module) that is installed in amplifier  10  and provides a signal to controller  70  (FIG. 2) indicating the presence/absence of such modules. Controller  70  then feeds this signal indicating the presence/absence of such modules to the headend controller  12 . This indication will aid in determining the appropriate amplifier configuration for proper system configuration at the headend controller  12 . Additional types of modules may be added in the future. 
     The following tables 1-3 describe exemplary voltage levels of signals detected by the status monitor circuit  30  for the different configurations of the amplifier  10 . The status monitor circuit  30  can read the voltage level of these signals and encode the data to inform the headend controller  12  of the amplifier&#39;s configuration. 
     Circuit  75  contains a pull-up/pull-down resistor  63  connected to line  61  to amplifier  10 . Also, different values for resistor  58 , shunted to ground, will be connected to status monitoring line  61  in each of the modules to indicate different module types. Table 1 indicates preferred voltages for the DC signal on line  61  for the corresponding type of module types. An example module type having reverse path circuitry  26  is shown in FIG.  1 . 
     
       
         
               
             
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Module Option Card Types 
               
             
          
           
               
                 Line 61 Voltage (V) 
                   
               
               
                 with V cc  at +5 V 
                 Module Type 
               
               
                   
               
               
                 1.38-1.64 
                 Fiber Module + Reverse Switch 
               
               
                 1.85-2.15 
                 Fiber Module 
               
               
                 2.33-2.67 
                 Reverse Module + Reverse Switch 
               
               
                 3.78-4.24 
                 Reverse Module 
               
               
                   
               
             
          
         
       
     
     Line  67  is used by the status monitoring circuit  30  to enable monitoring of the output configuration type of amplifier  10  (i.e.,_single, dual, or triple output) that is installed. Voltage level of the DC signal read on line  67  will aid the controller  70  in determining the amplifier output type for proper amplifier configuration. Additional types of amplifiers may be added in the future. Pull-up resistor (20 kΩ, 1%) Rv should connected to this amplifier detect line  67 . Different resistor values, Rg to ground will also be present on this amplifier detect line  67  in the mother board to indicate the different amplifier output types. Table 2 indicates preferred different voltages on the amplifier detect line  67  and the corresponding amplifier output type. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Amplifier Station Types 
               
             
          
           
               
                 Line 67 Voltage (V) 
                   
               
               
                 with power at +5 V 
                 Amplifier Type 
               
               
                   
               
               
                 0.20-0.59 
                 Single 
               
               
                 0.89-1.11 
                 Dual 
               
               
                 1.38-1.64 
                 Triple 
               
               
                   
               
             
          
         
       
     
     An AGC mode detect line  77  is used by the status monitoring circuit  30  to detect the presence or absence of the AGC control circuit  52  and will enable the status monitoring circuit  30  to detect if the amplifier&#39;s AGC control circuit  52  is in a thermal mode or an auto mode. A pull-up resistor  79  and a shunt resistor  62  is placed on this AGC mode line  77 . Resistor  62  will preferably have a value of approximately 80 Ω when AGC control circuit  52  contains the AGC function, and will preferably have a value of approximately 20 kΩ when the AGC control circuit  52  contains a thermal AGC. Additionally, resistor  62  is preferably an open circuit when the AGC function is not present. Table 3 indicates the three possible states and corresponding voltage levels for the DC signals on this AGC mode line  77 . 
     
       
         
               
             
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 AGC Operation 
               
             
          
           
               
                 Line Voltage (V) 
                 AGC Operation 
               
               
                   
               
               
                 4.0-5.0 
                 No AGC Installed 
               
               
                 2.0-3.0 
                 Thermal 
               
               
                   0-1.0 
                 Auto 
               
               
                   
               
             
          
         
       
     
     While the principles of the invention have been made clear in the illustrated embodiments, there will be immediately obvious to those skilled in the art many modifications of the structured arrangements, proportions, elements, materials, and components used in the practice of the invention, that are particularly adapted for specific environments and operational requirements without departing from those principals. The appended claims are therefore intended to cover and embrace any such modifications within the limits of the true spirit and scope of the invention.