Patent GB-780060-A (GB)
Title: Improvements relating to radio links
Inventor: KRAMSKOY CHARLES MARK
IPC: H04N5/38
Filed: 1954-04-29
Abstract: 780,060. Duplex radio signalling. ELECTRIC & MUSICAL INDUSTRIES, Ltd. April 12, 1955 [April 29, 1954], No. 12519/54. Class 40 (5). A radio link comprises normally operative means for radiating intelligence signals and interspersed synchronizing signals from a first point, normally operative means at a second point for receiving the intelligence and synchronizing signals, normally inoperative means for radiating other intelligence signals from the second point, normally inoperative means at the first point for receiving the other intelligence signals, switch means for rendering the first-mentioned radiating means inoperative and for rendering the second-mentioned receiving means operative during intervals following predetermined synchronizing signals, and switch means responsive to the predetermined synchronizing signals for rendering the secondmentioned receiving means inoperative for predetermined intervals. Referring to the drawing the microwave radio link comprises a control transmitter and a guidance receiver mounted in an aircraft, and a guidance transmitter and a control receiver mounted in a missile. The guidance transmitter comprises a television pickup tube 1, the output of which is combined with line and frame synchronizing signals and fed to a modulator oscillator 10. The output of the oscillator 10 is fed to an aerial 11 which is also connected, through a switch 12, to a control receiver of conventional design. Line and frame synchronizing signals are produced by a generator 7, and the frame synchronizing pulses are used to trigger a flip-flop 17 which cuts of the oscillator 10 and alters the switch 12 so that the control receiver is connected to the aerial 11 for a period of about 0.3 milliseconds after each frame; the flip-flop then reverts to its stable condition and restores the transmitter to its normal operative state and the receiver to its inoperative state. The control transmitter in the aircraft comprises a source of control signals 18 connected to an amplifier and a modulator oscillator 20, which may be of the same type as the modulator 'oscillator 10 and uses the same carrier frequency, e.g. 4000 mcs./sec. The oscillator 20 is connected to an aerial 21 which is also connected through a switch 22 to a television receiver circuit. An output from the frame scanning unit 31 is passed through a delay circuit 35 and used to trigger a flip-flop 34 which controls the switch 22 and the oscillator 20. The delay of the network 35 and the unstable period of the flip-flop 34 are predetermined to ensure that the intervals in which the control transmitter is rendered operative and the guidance receiver rendered inoperative are wholly enclosed by the intervals when the guidance transmitter is rendered inoperative and the control receiver is rendered operative; for example a guard interval of 0.1 milliseconds may be provided at the beginning and end of the interval when the control transmitter is operative to allow for the time taken for the signals to travel between the aircraft and the missile.