GB964572A - Improvements in signal processing - Google Patents

Abstract

964,572. Automatic phase control systems. RANK-BUSH MURPHY Ltd. March 30, 1961 [April 1, 1960], No. 11554/60. Drawings to Specification. Heading H3A. In magnetic tape-recording of television signals a plurality of cycles of a reference frequency is injected into recurrent blank intervals of the signals as from an oscillator whose oscillations are applied through a gate circuit into an adding circuit during the blanking intervals when the gate is opened by line sync. pulses in the signals. Alternatively, the oscillations may be produced by shock exciting a passive tuned circuit energized from the line sync. pulses. In reproducing the signals (from a tape controlled in mean speed from a separate parallel recording track) signal frequency variations resulting from variations about the mean speed are compensated by comparing the reference frequency bursts with oscillations of equal standard frequency in a phase detector whose output, in accordance with any phase error, varies the delay and hence phase shift produced by a variable delay ladder network in the path of the reproduced signals. The network may comprise potential variable shunt capacitors or current variable series inductors each hybrid connected with the control current source by a pair of magnetic cores preventing relative interaction.