GB1216750A - Synchronising periodic signals - Google Patents

Abstract

1,216,750. Automatic phase control. BRITISH BROADCASTING CORP. 1 Aug., 1969 [26 Sept., 1968], No. 45736/68. Heading H3A. A television synchronizing system comprises: an oscillator at a local station which generates a synchronizing waveform; means for comparing it with a synchronizing waveform received from a remote station to classify the phase error, the classification including a zero error class comprehending a finite range of errors about zero error; an error signal channel 20 transmitting to the remote station a coded signal indicating the class of the error; means 17 for applying a reference signal from the local station oscillator to the remote station; and means at the remote station for deriving from the reference signal, a synchronizing signal for the remote station which may be varied in frequency in dependence on the signal on channel 20 to reduce the phase error. As described, the reference signal 17 is fed to a divider 16 the output from which provides a signal for triggering the remote synchronizing generator 14. The error signal 20 is decoded at 18 to produce a signal which controls the division ratio of unit 16 via switch 19. When no video signal is being transmitted on line 12 from the remote to the local station, the signal on line 20 changes over switch 19 to the position shown, and the remote synchronizing signal is controlled by comparing it with a signal on line 21 in comparator 15.