GB496119A - Improvements in or relating to television and like transmitting systems - Google Patents

Abstract

496,119. Valve circuits. WHITE, E. L. C. April 23, 1937, No. 11607. [Class 40 (v)] An impulse generator is started and stopped by control impulses, the starting and stopping pulses originating from a single signal passing along a delay network. In Fig. 1, valve 1 of a multivibrator is started into operation when a pulse passing through delay network 11 reaches tapping 13 and is stopped when the same pulse reaches tapping 16, a square topped wave of the duration determined by tappings 13, 16 being generated and fed to output terminals 20, 21. Instead of a single delay network two delay networks coupled by an amplifier or buffer stage may be used. Alternatively separate delay networks for the starting and stopping pulses may be used as shown in Fig. 3. In this embodiment the discharge through hexode 30 is controlled by pulses applied to grids g<1> and g<3>. Normally grid g<1> is biassed to cut off. The control pulses must be of longer duration than the output pulses required. When the starting pulse is received grid g<1> allows current to pass and when the stopping pulse is received grid g<3> is biassed to cut-off so that current reaches output terminal 42 during the interval between the two pulses. If the control pulses are of saw tooth form the duration of the controlled pulse can be varied by altering the biasses on grids g<1> and g<3>. The invention is described for generating synchronizing pulses for television. Specifications 456,650 and 456,840 are referred to.