Bi-directional digital communication network

• US 4,041,398 A
• Filed: 06/03/1976
• Issued: 08/09/1977
• Est. Priority Date: 06/03/1976
• Status: Expired due to Term

• Current Assignee: ICC, Inc.
• Original Assignee: ICC, Inc.
• Inventors: Ellis, Michael L.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/692,487
• Time in Patent Office: 432 Days
• Field of Search: 178/2 R, 178/2 C, 178/2 D, 178/2 E, 178/3, 178/4.1 B, 178/58 R, 178/4.1 R, 179/2 DP, 179/2 C, 325/37, 325/308, 325/309, 358/86
• US Class Current: 725/131
• CPC Class Codes: H04L 5/143 for modulated signals H04L5/1469 takes precedence
• CPC Class Codes: H04N 2007/17372 the upstream transmission being initiated or timed by a signal from upstream of the user terminal
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A bi-directional digital communication unit for requesting the performance of services by transmitting data to a central computer complex for purposes of processing the data to utilize it to initiate the performance of the requested services and for receiving data from the central computer complex for purposes of determining whether the request for the performed services was received and the performance of the requested services was initiated. Data is transmitted from the central computer to the communication unit on a carrier wave at a first low frequency F₁ and data is transmitted from the communication unit to the central computer at a second low frequency F₂. The data received by the system, on the carrier wave having frequency F₁, is demodulated and applied to valid address check means to determine if the central computer has transmitted a valid address to the unit. A modem register provides a data word which identifies the services that are requested by the user and transmits this data word to a data shift register which, if the system has received a valid address from the central computer, transmits the data word to the central computer, on a carrier wave at frequency F₂, to initiate the performance of the requested services. The system includes a receiver data register which, after a subsequent valid address by the central computer of the communication system, registers the receipt by the unit of a data word from the central computer signifying the receipt by the central computer of the request for services, and controls visual displays in the modem control code generator to visually inform the user of the receipt by the central computer of the data word generated by the modem control code generator and the initiation of the performance of the requested services. The system includes a master clock frequency divider and control logic for providing timing and logic pulses to synchronize the operation of the system and coordinate it with that of the central computer.

Claims

1. A low frequency bidirectional digital communication unit for use over coaxial cables of the cable TV system type, for requesting the performance of services by transmitting data to a central computer comprising:

address byte register means for registering an address codeword associated with said unit,

modem control code register means for registering a data word corresponding to services requested by said unit,

shift register means coupled to said address byte register means and said modem control code register means for receiving the contents of said address byte register means and the contents of said modem control code register means in parallel and for shifting said address codeword and said data word out of said data shift register serially to provide a serial output to the central computer on the coaxial cable, and

transmitter modulator means coupled to the serial output of said shift register means for transmitting said serial output of said shift register means to said central computer on a low frequency carrier wave to request the performance of services.

2. The unit as described in claim 1 and further including multiplexer means coupled between said address byte register means and said shift register means and further coupled between said modem control code register means and said shift register means to transmit the contents of said address byte register means and the contents of said modem control code register means to said shift register in accordance with a predetermined sequence.

3. The unit as described in claim 2 and further including control logic means coupled to said multiplexer means for controlling said multiplexer means to transmit the contents of said address byte register means and the contents of said modem control code register means to said shift register means in accordance with said predetermined sequence.

4. The unit as described in claim 1 and further including means coupled to said modem control code register means for receiving a data word from said central computer for registering the receipt by the central computer of the data word in said modem control code register means corresponding to services requested by said unit.

5. The unit as described in claim 4 and wherein said means for receiving a data word from said central computer includes

receiving means for receiving said data word carried by a low frequency carrier wave from the central computer, and

receiver data register means coupled to the output of said receiving means and to the input of said modem control code register means for registering the receipt of a data word indicative of the receipt by the central computer complex of the data word in said modem control code register means corresponding to services requested by said unit.

6. The unit as described in claim 5 and wherein said modem control code register means includes visual display means for providing a visual display of the data word registered therein and,

said receiver data register means is coupled to said visual display means to provide a visual indication of the receipt by said central computer of said data word registered in said modem control code register means corresponding to the services requested by the unit.

7. The unit as described in claim 6 and further including control logic means coupled to the output of said receiving means and responsive thereto for generating control pulses, said control logic means being coupled to said receiver data register means for controlling said receiver data register means to synchronize the operation of said receiving means with the operation of said receiver data register means.

8. The unit as described in claim 7 and further including multiplexer means coupled between said address byte register means and said shift register means and further coupled between said modem control code register means and said shift register means, said multiplexer means being coupled to said control logic means and responsive thereto to transmit the contents of said address byte register means and the contents of said modem control code register means to said shift register means in accordance with a predetermined sequence.

9. The unit as described in claim 1 and further including auxiliary power supply means and wherein said modem control code register means includes visual display means coupled to said auxiliary power supply means for providing a visual display indicative of the state of operation of said auxiliary power supply.

10. The unit as described in claim 1 and further including:

an alarm device for providing an alarm, when set to its normal mode of operation, in the event of a security breach,

said modem control register means including a security channel coupled to said alarm device for providing a data word to signal an alarm, said security channel including false alarm checking means for preventing said security channel from being activated unless said alarm has been armed and is operating in the normal mode of operation.

11. A method of transmitting address codewords and data words in a cable TV system over a coaxial cable between a bidirectional subscriber communication unit and a central computer complex comprising the steps of:

transmitting at a first low frequency a plurality of address codewords from said central computer complex to each said subscriber unit in successive order;

receiving each of said plurality of address codewords at said unit;

comparing each of said address codewords with an internally hard-wired address codeword associated with each said unit for ascertaining the receipt by said unit of a valid address codeword identifying said unit from the central computer complex;

transmitting at a second low frequency said address codeword associated with said unit and a data word identifying services including television programming desired at the location of said unit from said unit to said central computer complex subsequent to the receipt by said unit of a valid address codeword from said central computer complex; and

transmitting a confirmatory data codeword from said central computer complex associated with the address codeword identifying the originating communication unit.

12. A method as defined in claim 11 further including the step of decoding the confirmatory signal at the unit and providing a local indication of the services represented by the confirmatory signal.

13. A method as defined in claim 11 further including the step of filtering out undesired signals including television signals at the input to said communication unit.

14. In a cable TV type system for transmitting requests for services between a plurality of receiving stations, each having associated bidirectional communication units, and a central computer and service supplying complex, the improvements comprising:

means at each said communication unit for registering a unique address codeword associated with said unit;

means at each said communication unit for periodically receiving and recognizing digital address codewords transmitted to said communication unit at a first predetermined low frequency, and in a predetermined time slot allocated to each cable TV subscriber;

means at each said communication unit for registering service requests including television programming requests originated by the cable TV subscriber at the location of said communications unit, in digital form;

means at each said communication unit for transmitting to the central computer and service supplying complex, a digital signal including first the unique address of the communications unit, and secondly, the nature of the service request at a second predetermined low frequency; and

means at each said communications unit for receiving a confirmatory digital signal, including both the unique address and the desired service codes, transmitted at said first predetermined low frequency, and for verifying the correctness of the implemented service signal being sent back from the central complex.

15. A system as defined in claim 14 further comprising at least one coaxial cable for bidirectional communication with said communication unit.

16. A system as defined in claim 14 further comprising means included in said receiving means for accepting said first low frequency, and for filtering out signals at other frequencies.

17. A system as defined in claim 14 wherein said first and second low frequencies are both in the range from 50 to 400 kilohertz.

18. In a Pay TV type system for transmitting requests for services between a plurality of receiving stations each having associated bidirectional communication units, and a central computer and service supplying complex, the improvements comprising:

means at each said communication unit for registering a unique address code word associated with said unit;

means at each said communication unit for periodically receiving and recognizing digital address codewords transmitted to said communication unit at a first predetermined low frequency, and in a predetermined time slot allocated to each Pay TV subscriber;

means at each said communication unit for registering service requests including television programming requests, originated by the Pay TV subscriber at the location of said communications unit, in digital form;

means at each said communication unit for transmitting to the central computer and service supplying complex, a digital signal representing the nature of the service request in the response time period allocated to each specific communication unit, at a second predetermined low frequency; and

means at each said communications unit for receiving a confirmatory digital signal, including both the unique address and the desired service codes, transmitted at said first predetermined low frequency, and for verifying the correctness of the implemented service signal being sent back from the central complex.

19. A system as defined in claim 18 further comprising:

at least one coaxial cable for bidirectional communication with said communication unit, and

means included in said receiving means for accepting said first low frequency, and for filtering out signals at other frequencies.

20. A system as defined in claim 18 further comprising:

shift register means for registering an address codeword associated with said unit, and

valid address check means having one input coupled to said receiving means and a second input coupled to said shift register for comparing said address codeword received from said central computer with said codeword associated with said unit for checking for the receipt by said unit of a valid address from said central computer complex.

21. A system as defined in claim 18 further comprising:

a master oscillator for providing a signal having a frequency equal to said first low frequency, and

phase-lock detector means for synchronizing the phase of said first low frequency signal with the phase of said signal provided by said master oscillator.

22. A system as defined in claim 18 wherein said first and second low frequencies are both in the range from 50 to 400 kilohertz.