GB847703A - Improvements in or relating to television apparatus - Google Patents

Abstract

847,703. Television. PYE Ltd. March 10, 1959 [March 10, 1958], No. 7596/58. Class 40(3). [Also in Group XL(c)] Distortion in television signals originating at a remote point is removed prior to feeding such signals to a television transmitter. As shown, the D.C. component is first restored by means of a clamp 6 and the signals fed, with negatively going synchronizing signals, to an amplifier stage V1 the cathode circuit of which includes a rectifier MR1 so biased that it conducts only during the occurrence of the synchronizing signals and effectively connects the decoupling capacitor Cl across cathode resistor R1. The gain of V1 is therefore increased and synchronizing signals of enhanced amplitude are produced in the anode load circuit which consists of a valve V2 shunted by a clipping stage V3. The latter cuts-off at a level determined by RV2 to produce "clean" synchronizing pulses the clipping action being improved by the anode load changing from the low resistance of V3 when conducting to the high resistance of V2. The complete waveform at the anode of V3 is then fed to a similar arrangement V4, V5 and V6 of which the latter operates as a peak white limiter and delivers a "cleaned-up" complete television waveform to a plurality of outputs 5. The circuit may also be employed to insert blanking pulses in a television signal received directly from a camera by operating V3 as a black level clipper to the grid of which the blanking pulses are supplied. For vertical shade correction suitable signals may by inserted in the clamp circuit or applied to the grid of V2.