GB654154A - Improvements in or relating to frame-synchronization in television receivers - Google Patents

Abstract

654,154. Pulse discriminating circuits. PHILIPS LAMPS, Ltd. July 11, 1947, No. 18416. Convention date, July 15, 1946. [Class 40 (vi)] [Also in Group XL (b)] In a television receiver in which the frame synchronization signals comprise a long pulse interrupted by short pulses preferably at the line frequency, or a multiple thereof, and in which the synchronizing signals after integration are fed to a control electrode of an electronic discharge device which is also controlled by the original synchronizing signals to deliver a control voltage for triggering the frame time-base generator, a voltage derived from the time-base generator is fed back to the electronic discharge device in such a form as to ensure that only the first of said interruptions in each frame synchronizing signal shall be effective in causing the said discharge device to deliver a frame synchronizing impulse. A composite signal of the form shown by v<SP>1</SP> of Fig. 2, is fed to the grid 1 of a valve 2 and through a phase reversing device 3 and an integrating network 4 to a second control grid 5 so that the output from the anode 6 would be as indicated by v<SP>3</SP>, the output being differentiated by a device 7 to form a number of pulses v4 having positive peaks capable of triggering the frame saw-tooth generator. A saw-tooth wave as indicated by v<SP>5</SP>, derived from the saw-tooth generator, is modified by a condenser 9 and resistance 10 to the form indicated by v<SP>6</SP> and is fed to the control grid 1 of the valve 2 so that with the combined grid control voltage, as indicated by v<SP>1</SP>, solely a single impulse corresponding to the first interruption in the frame impulse is passed to the network 7 and the frame time-base generator. The Specification as open to inspection under Sect. 91 includes a modification, Fig. 3, (Cancelled), in which a voltage similar to v<SP>1</SP> is applied to a grid 12 of the hexode part of a double valve 13, is reversed in phase and integrated in combination with a condenser 16 and is applied via a condenser 18 and resistance 19 to act as a control voltage, the anode 20 of the triode part of the discharge tube, the voltage on the anode 20 being applied to a circuit controlling a frame saw-tooth generator. The voltage set up on the grid 23 is similar to that indicated by v<SP>1</SP> but reversed in polarity so that when v<SP>1</SP> becomes negative, pulses are sent from the anode 20 and will normally be similar to those indicated by the curve v<SP>9</SP>, Fig. 2 (Cancelled). A voltage from the pentode 28 forming the final valve of the frame time-base generator is differentiated by condenser 27 and resistance 26 and a voltage similar to the form indicated by v<SP>6</SP>, but reversed in polarity, is applied to the grid 23 so that the triode part of the hexode becomes conducting and cuts off the output at the anode 20 after the transmission of the first interrupting pulse has triggered the frame generator. This subject-matter does not appear in the Specification as accepted.