GB491873A - Improvements in modulated carrier wave receivers - Google Patents

Abstract

491,873. Television receivers. BRITISH THOMSON - HOUSTON CO., Ltd., and WATSON, D. S. March 11, 1937, No. 7188. [Class 40 (iii)] The mixed picture and synchronizing signals are applied over a direct-current connection to the grid of a pentode V2, Fig. 1, whose anode current is saturated for picture signals and is cut off for synchronizing signals, so that the synchronizing signals are isolated. Line and frame synchronizing signals are separated by two condenser-resistance combinations A, B ; the frame synchronizing signals are preferably applied to a further limiting pentode V3 whose output controls the frame oscillator. The circuits A, B may have their time-constants varied under the control of switches to adapt the receiver for use with transmitters employing either interlaced or sequential scanning. In a modification, the circuit B is replaced by a circuit C, Fig. 2a, the synchronizing pulses charging the condenser C, so that a frame impulse comprising a rapid succession of short impulses will charge the condenser to a potential sufficient to cut off the anode current of valve V3. The direct-current components of the mixed signal may be inserted, if absent, by the resistance R1, Fig. 1, and condenser C1 in the grid-cathode circuit of the final amplifier VI.