GB537878A - Improvements in television synchronizing-signal separators - Google Patents

Abstract

537,878. Television synchronizing-signal separator. HAZELTINE CORPORATION. Feb. 19, 1940, No. 3138. Convention date, March 16, 1939. [Classes 40 (iii) and 40 (v)] Undesired random pulses are removed from received synchronizing television signals by first deriving from said signals a first signal limited to an amplitude of less than twice the amplitude of the desired pulses, and also a second signal having periodic maximum values corresponding in periodicity and phase with the desired pulses and in which the undesired random pulses appear if at all in a time distribution substantially different from that of the corresponding received random pulses, adding the two derived signals, and limiting the resultant to obtain the desired pulses. The apparatus enclosed within the dotted lines 21, Fig. 1, serves to separate the frame signals from line signals and from random signals as follows. The mixed signal a, Fig. 2, is fed by means of condenser 28 and resistance 29 to valve 30 having an output network 31, these devices being designed to limit the output to the part below the dotted line shown along signal a. The limited signal is then applied to a diode 33 and to a reflecting network 32 which feeds the delayed reflected signal also to the diode. The network operates as more fully described in Specification 531,712. The delay exceeds the width of line pulses x but is less than the width of frame pulses y, so that the combined signal appears as at b, Fig. 2. The diode is biased by means of resistance 36 and condenser 37 to limit the signal to the part above the dotted line shown along signal b. Hence the final output is as shown at d, Fig. 2, substantially pure frame pulses. The devices 22, 23, 24, Fig. 1, the device 23 being a. delay network, operate in somewhat similar fashion to isolate line pulses. In these devices, the delay is equal to the line scanning period, so that the line pulses add up while the irregular random pulses do not and are removed by the limiting operation. Specifications 491,728, 514,271 and 518,434 also are referred to. The Specification as open to inspection under Sect. 91 also comprised the subject-matter now described in Specification 538,587. This subject-matter does not appear in the Specification as accepted.