Communication system for the transmission of closed circuit television over an ordinary pair of wires

• US 4,054,910 A
• Filed: 02/26/1976
• Issued: 10/18/1977
• Est. Priority Date: 02/26/1976
• Status: Expired due to Term

• Current Assignee: Tel-E-Tel Incorporated
• Original Assignee: Tel-E-Tel Incorporated
• Inventors: Chou, Wayne W., Erett, Richard
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/661,530
• Time in Patent Office: 600 Days
• Field of Search: 178/6, 178/59, 178/61, 178/DIG. 13, 325/308, 330/30 D, 333/12, 358/86
• US Class Current: 725/78
• CPC Class Codes: H04B 3/04 Control of transmission; Equalising
• CPC Class Codes: H04N 7/108 the cable being constituted by a pair of wires

Abstract

A communication system is provided which allows closed circuit television pictures to be transmitted from conventional TV cameras to conventional monitors via an ordinary pair of wires, for example, telephone wires, lamp cord, BX cable, etc., over limited distances without measurable degradation of picture quality. A balanced system is provided with dual inputs and outputs so that the system can accommodate simultaneous transmission of audio or other data. Adapters are provided on the receiving end and on the sending end which provide conversion, impedance matching, and the frequency compensation required in order to provide uniform frequency response for the quality transmission of television as well as audio and/or other data.

Claims

1. A communications sytems for the transmission from a television camera or other transmitter of different type signals to a monitor of closed circuit television signals or receiver for said different type signals over an ordinary pair of wires, comprising

a. a transmitter adapter connected to an ordinary pair of wires for coupling a televison camera to said pair of wires,

b. said transmitter adapter including transmitter differential amplifier means having a transmitter frequency compensation network coupled thereto,

c. a receiver adapter connected to said ordinary pair of wires at a desired distance from said transmitter adapter for coupling a television monitor to said pair of wires,

d. said receiver adapter including receiver differential amplifier means having a transmitter compensation network coupled thereto,

e. said transmitter and receiver differential amplifier means each having a pair of input terminals coupled to a differentially connected, emitter-coupled transistor pair,

f. said transmitter and receiver frequency compensation networks each having mid-band and high-band frequency compensation networks coupled between the emitters of said emitter-coupled transistor pair for providing frequency compensation for transmission losses through said pair of wires,

g. said mid-band frequency compensation means comprising a potentiometer having a slide thereon coupled to a capacitor which is coupled to one side of said potentiometer, in which the gain of said differential amplifier means increases with frequency as said slide is moved from a shortened position with respect to said capacitor to the other extreme on said potentiometer.

2. A communication system for the transmission from a television camera or other transmitter of different type signals to a monitor of closed circuit television signals or receiver for said different type signals over an ordinary pair of wires, comprising

a. a transmitter adapter connected to an ordinary pair of wires for coupling a television camera to said pair of wires,

b. said transmitter adapter including transmitter differential amplifier means having a transmitter frequency compensation network coupled thereto,

c. a receiver adapter connected to said ordinary pair of wires at a desired distance from said transmitter adapter for coupling a television monitor to said paid of wires,

d. said receiver adapter including receiver differential amplifier means having a transmitter compensation network coupled thereto,

e. said transmitter and receiver differential amplifier means each having a pair of input terminals coupled to a differentially connected, emitter-coupled transistor pair,

f. said transmitter and receiver frequency compensation networks each having mid-band and high-band frequency compensation networks coupled between the emitters of said emitter-coupled transistor pair for providing frequency compensation for transmission losses through said pair of wires,

g. said high frequency compensation means comprising a plurality of switches and serially coupled capacitors coupled in shunt, with one of said capacitors representing the smallest increment of capacitance which can be switched in with additional switching providing increasingly larger increments of capacitance for providing compensation in the high-frequency end of the transmission band.

3. A communications system for the transmission from a television camera or other transmitter of different type signals to a monitor of closed circuit television signals or receivers for said different type signals over an ordinary pair of wires, comprising

a. a transmitter adapter connected to an ordinary pair of wires for coupling a television camera to said pair of wires,

b. said transmitter adapter including transmitter differential amplifier means having a transmitter frequency compensation network coupled thereto,

c. a receiver adapter connected to said ordinary pair of wires at a desired distance from said transmitter adapter for coupling a television monitor to said pair of wires,

d. said receiver adapter including receiver differential amplifier means having a transmitter compensation network coupled thereto,

e. said transmitter and receiver differential amplifier means each having a pair of input terminals coupled to a differentially connected, emitter-coupled transistor pair,

f. said transmitter and receiver frequency compensation networks each having mid-band and high-band frequency compensation networks coupled between the emitters of said emitter-coupled transistor pair for providing frequency compensation for transmission losses through said pair of wires,

g. said transmitter and receiver adapters each having differential connected inputs an outputs, respectively, and

h. said differential inputs having said television camera connected to one input thereof and a multiplex transmitter connected to the other input thereof and said differential outputs having said monitor connected to one output thereof for receiving signals from said television camera and receiver means connected to the other output thereof for receiving signals from said multiplex transmitter which system provides isolation between each input and output thereof to prevent interaction therebetween.