APPARATUS FOR AUTOMATIC SENSING OF LINE AMPLIFIER CONFIGURATION FOR STATUS MONITORING

Abstract: An apparatus for indicating the configuration of a cable television line amplifier (26). The line amplifier contains a controller (70) that senses a preset voltage on a status indication line. When the amplifier is reconfigured, such as by adding new circuits containing new functions of 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: APPARATUS FOR AUTOMATIC SENSING OF LINE AMPLIFIER CONFIGURATION FOR STATUS MONITORING 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'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'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 amplifier 10 is fed through variable loss inserter 36 or attenuator, and directed though 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 filters 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 circuitry 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 60 disposed on circuitry 24. Status monitor circuitry 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 circuity 52 is not installed, status monitor circuitry 30 is fed a DC signal having third voltage level on AGC mode line 77. The third voltage level is generated by pull-up resister 79. If AGC circuit 52 is installed, status monitor circuitry is fed on line 77 a DC signal having a voltage level set by pull down resister 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 circuitry 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 configuration of amplifier 20. This status signal is fed through reverse amplifier 68 and reverse path filter 49 to 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 10 outputs (i.e. single, dual, triple output). Resistor 62 is disposed within removable circuit 52. Circuit 52 that may be added to the amplifier 26 either in the amplifier production or after the amplifier 26 has been installed in the field. Referring to Fig 2, there is shown the status monitoring circuitry 30, having a controller 70 that reads the DC signals from the AGC circuit 52 through analog-to-digital (A D) converter 72 and DC signals from the reverse path circuit 24 through A/D converter 74. Controller reads DC signals on line 67 from A/D converter 71. Controller 70 is connected to a test interface 76, controller 70 sends and receives signals to interface 76 to permit a technician to connect test equipment thereto to indicates the AGC circuit 52 reverse path circuit 24 and indicator circuit 64 configuration. Controller 70 uses A/D converter 78 to read values from the RF detector 50, and to read and store the value of the signal from A/D connector 78 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 75 (Fig. 1). Referring to Fig. 1 detect circuit 75 includes A/D converter 74, line 61 and circuit 60. Circuit 75 monitors the type of module (i.e. distribution reverse amplifier or fiber) installed in amplifier 10 and will provide 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 is then fed to controller 12. This indication will aid in determining the appropriate amplifier 10 configuration for proper system configuration at the headend 12. Additional types of modules may be added in the future. The following tables 1-3, describe exemplary voltages levels of signals detected by the status monitor circuitry 30 for amplifier 26 different configurations. The status monitor circuitry 30 can read the voltage level of these signals and encode the data to inform the headend 12 of the amplifier 10 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) Module Type with V cc at +5V 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 circuitry 30 to enable monitoring of the type of amplifier 10 (single, dual, triple) installed. Voltage level of the DC signal read on line 67 will aid the controller 70 in determining the amplifier 10 type for proper amplifier configuration. Additional types of amplifiers may be added in the future. Pull-up resistor (20 kΩ, 1%) R v should connected to this amplifier detect line 67. Different resistor values, R<j, to ground will be present on this amplifier detect line 67 in the mother board to indicate different amplifier types. Table 2 indicates the preferred different voltages on the amplifier detect line 67 and the corresponding amplifier type. Table 2: Amplifier Station Types Line 67 Voltage (V) Amplifier Type with power at +5V 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 circuitry 30 to detect the presence or absence of the AGC and will enable the circuitry 30 to detect if the amplifier's AGC is in a thermal or an auto mode. A pull-up resistor to 79, and a shunt resistor 62 is placed on this AGC mode line 77. Resistor 62 will preferably have a value of approximately 80Ω in the when circuitry 52 contains the AGC function, and will preferably have a value of approximately 20 kΩ when circuitry 52 contains thermal AGC and Resistor 62 is preferably open circuit when no 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 are structured arrangements proportions, elements, materials, and components used in the practice of the invention, in otherwise which 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 only of the true spirit and scope of the invention.

Claims: What is claimed is: 1. An apparatus for indicating the configuration of a cable amplifier, the apparatus comprising: a circuit having a status indication line with a preset voltage level; a first removable module type connected to the circuit, said first card type having means for modifying the preset voltage level on the status indication line to a voltage level different from the preset voltage level; and a controller connected to the circuit for detecting the voltage level on the status indication line and for providing an indication to a headend the card type connected to the circuit. 2. The apparatus as recited in claim 1 wherein the circuit includes an input terminal having a video signal thereon, and an output means for amplifying the signal on the input and feeding the amplified signal to the output terminal . 3. The apparatus as recited in claim 1 wherein the modifying means includes a resister connected between the status indication line and ground. 4. The apparatus as recited in claim 1 wherein the circuit is coupled to a power line, and wherein the modifying means includes a resister connected between the status indication line and the power line. 5. The apparatus as recited in claim 1 wherein said controller provides an indication of the card type from one selected from the group consisting of fiber module, reverse modules, a combination of fiber module and reverse switch, and a combination of reverse module and reverse switch. 6. The apparatus as recited in claim 1 wherein said controller provides and indication that the amplifier is from the group consisting of a single amplifier, dual amplifier and triple amplifier. 7. A cable line amplifier comprising: a circuit having a status indication line with one of a plurality of preset voltage levels, said preset voltage levels corresponding to a different function of the amplifier; and a controller connected to the circuit for detecting the voltage level on the status indication line and providing an indication of a card type connected to the circuit as a function of the voltage level detected. 8. The amplifier as recited in claim 7 further comprising a first removable card type connected to the circuit, said first card type having a resister connected to the status indication line for modifying the preset voltage level on the status indication line to a voltage level different from the preset voltage level. 9. The amplifier as recited in claim 7 where in the functions consist of one selected from the group of AGC installed, Thermal AGC installed and no AGC installed. 10. The amplifier as recited in claim 7 wherein the function indicates that the amplifier is of the type consisting of a single, a dual or a triple. 11. The amplifier as recited in claim 7 wherein the controller provides the indication to a headend over an RF link. 12. A method for indicating the configuration of a cable line amplifier comprising the steps of: providing a circuit within the line amplifier having a status indication line with one of a plurality of preset voltage levels; setting the preset voltage levels on the status indication line to correspond to a different function of the amplifier; detecting with a controller connecting to the circuit the voltage level on the status indication line; and providing an indication of the module type connected to the circuit as a function of the voltage level detected. 13. The method as recited in claim 12 further comprising the step of feeding the indication of the module type connected to a headend through a cable television delivery system. 14. The method as recited in claim 12 further comprising the steps of connecting a new module type to the circuit; modifying the preset voltage level on the status indication line to a voltage level different from the preset voltage level when the new card type is connected; and providing an indication of the new module type when connected to the circuit. 15. The method as recited in claim 14 further comprising the step of providing on the new module type a resister connected to the status indication line; and modifying the preset voltage level on the status indication line with the resister. 16. The method as recited in claim 14 further comprising the step of indicating that the module consists of one selected from the group of AGC installed, thermal AGC installed and no AGC installed. 17. The method as recited in claim 14 further comprising the step of indicating that the amplifier is of the type consisting of a single, a dual or a triple. 18. The method as recited in claim 14 further comprising the step of indicating that the module type is one selected from the group consisting of fiber module, reverse modules, a combination of fiber module and reverse switch, and a combination of reverse module and reverse switch.

Inventors: BRICKELL JOHN W, NASH WAYNE H, BRICKELL, JOHN, W., NASH, WAYNE, H.
Applicants: BRICKELL JOHN W, NASH WAYNE H, SCIENTIFIC ATLANTA, BRICKELL, JOHN, W., NASH, WAYNE, H., SCIENTIFIC-ATLANTA, INC.
Application year: 1997
Main classification: H04B3
IPC codes: H04B3, H04N7, H04N17