GB541005A - Television synchronizing and control system - Google Patents

Abstract

541,005. Television synchronizing system. HAZELTINE CORPORATION. Sept. 16, 1939, No. 25996. Convention date, Oct. 5, 1938. [Classes 40 (iii) and 40 (v)] Synchronizing pulses are separated from negatively modulated television signals for controlling line and field frequency generators and producing automatic volume control as follows : The signals taken for example from the intermediate frequency amplifier 14, Fig. 1, of a receiver are fed by condenser 22 and resistance 23 to an amplifying valve 20 coupled by a transformer 25 to a diode rectifier 21, the circuit of which includes a resistance 27 and a condenser 28 having a time constant considerably greater than the period of the line synchronizing pulses whereby a voltage e, Fig. 2, is developed across the resistance 27 depending on the synchronizing peak pulses S in the signal train. The voltage e is smoothed by a filter circuit 31, 32 and is used to control bias in the radio and intermediate frequency amplifiers 12, 14 and in the oscillator modulator 13. A low resistance 29 is also inserted in the circuit of the diode 21 either as in Fig. 1 or as in Fig. 3, and the voltage i, Fig. 2, developed on this resistance in accordance with the synchronizing pulses is fed to the line and frequency generators 18, 19. Specifications 363,605, 444,049, 444,881, 445,428 and 541,006 are referred to.