GB542258A - Television systems and synchronising means therefor - Google Patents

Abstract

542,258. Television. STANDARD TELEPHONES & CABLES, Ltd. Oct. 16, 1940, No. 15336. Convention date, Oct. 19, 1939. [Class 40 (iii)] A television transmitter is adapted to generate a composite synchronizing signal comprising usual unidirectional pulses at line frequency and pulses of high frequency waves at frame frequency. As shown in Fig. 1, unidirectional pulses 24 from a conventional synchronizing generator 10 are fed to a frequency multiplier 11 yielding pulsations 13 at 529-2 k.c. This high frequency 13 is supplied to an amplifier 15 unblocked by pulses 16 at frame frequency from the generator 10, so that the output of this amplifier is a series of pulses 12, each constituted by a short train of high frequency. These pulses 12 and the usual line pulses 14 from the generator 10 are mixed by means of the two valves 35, 3'6 and fed through a cathode load-stage of low impedance 41 to the transmitter 20, which receives the video signal from a cathode-ray tube 29 synchronized and blanked by pulses from the common generator 10. The high frequency train at frame frequency produced by this circuit extends on both sides of the axis and may be clipped by a valve circuit, Fig. 3 (not shown), the negative peaks being first clipped by one valve 42 and the opposite peaks by a subsequent valve 43. A receiver for this television signal is described in Specification 550,631. The Specification as open to inspection under Sect. 91 describes also a receiver circuit generally similar to that described in Specification 542,259 but different in details therefrom. This subjectmatter does not appear in the Specification as accepted.