GB483372A - Improvements in or relating to television and other signal transmission systems - Google Patents

Abstract

483,372. Television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Sept. 15, 1936, No. 25163. Convention date, March 26. [Classes 40 (iii) and 40. (v)] During synchronizing or other pauses short wave-trains are transmitted having an amplitude characteristic of the momentary values of the lower frequency and direct-current components of television signals. At the transmitter, the higher-frequency signals pass through a high-pass filter HP1 to line L, the L.F. signals passing through a low-pass filter to a device M, shown in Fig. 4, which modulates these signals on a carrier during the synchronizing pause. At the receiving station the H.F. signals pass through filter HP2 direct to the receiver, and the short wavetrains pass to a detector D, the rectified currents passing through a low-pass filter TP2 and being superposed on the H.F. signals. The device M, Fig. 4, may comprise an oscillator O, pushpull modulator P, and an electronic relay S1 energized by impulses d synchronized with the line deflecting potentials. The detector D, Fig. 5 (not shown), includes an electronic relay (synchronized with S1) a demodulator and a low-pass filter which rejects highfrequencies produced in the electronic relay and smooths the rectified impulses to reproduce the L.F. components. The Specification, as open to inspection under Sect. 91, also states that the short wavetrains may have their phase or frequency determined by the L.F. components and describes a system in which the amplitude of the received synchronizing impulses is used to re-introduce the L.F. components. Impulses of one direction charge a condenser C, Fig. 5 (Cancelled), through a crystal or valve rectifier G, the charge on the condenser being dependent on the amplitude of the impulses and serving to determine the controlling voltage on an amplifier. Synchronizing impulses may be derived from this circuit with the aid of an additional rectifier and bias battery, Fig. 6 (Cancelled) (not shown). By using a synchronizing impulse of the form shown in Fig. 8 (Cancelled), an A.V.C. voltage may be derived, Fig. 9 (Cancelled) (not shown). This subjectmatter does not appear in the Specification as accepted.