GB541006A - Television synchronizing and control system - Google Patents

Abstract

541,006. Television receiving circuits. HAZELTINE CORPORATION. Sept. 16, 1939, No. 25997. 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 23 and resistance 24 to an amplifying valve 20 coupled to diode rectifiers 21, 22 by a transformer having tuned primary 25 and secondary 26 with stabilizing resistances 25b, 26b. The diode 22 has in its circuit a resistance 29 with a condenser 30 developing a voltage e, Fig. 2, from the peak synchronizing pulses S of the signal; and these voltage pulses are led to the line and field frequency generators 18, 19. The other diode 21 includes in its circuit a resistance 27 with a condenser 28 having a time constant considerably greater than the period of the line synchronizing pulses, whereby a voltage variation depending on the amplitude of the pulses S is developed across the resistance 27 and fed through a filter 31, 32 to control the bias of the radio and intermediate frequency amplifiers 12, 14 and the oscillator modulator 13. A tapping 35 at the end of a resistance 33 serves to bias the diode 22 from the voltage along the resistance 27. Specification 541,005 is referred to. Reference has been directed by the Comptroller to Specifications 363,605, 444,049, 445,428 and 497,116.