GB624561A - Improvements in or relating to electrical signalling systems - Google Patents

Abstract

624,561. Pulse modulation. JEFFERSON, S., LEWIS, W. B., and STARR, A. T. July 4, 1945, No. 17106. [Class 40 (v)] [Also in Group XXXVIII] Spaced identifying or interrogating pulses are applied to a delay device for storing an early pulse and re-delivering it in coincidence with a later pulse, the occurrence of a coincidence actuating responding equipment. As applied to the system disclosed in Specification 584,670 and 624,558 in which two stations transmit pulses modulated on to carrier of the same frequency, each station precedes its sequence of pulses by an identifying pulse of constant width distinctively spaced from the sequence ; at the receiver, the received signal is applied at T1, Fig. 1, to the control grid of a valve V10 over a delay network DN, and to the suppressor grid of the same valve over a differentiating circuit C1, R1, which reduces the first pulse of the sequence to a pulse of the same width as the identifying pulse ; if coincidence occurs, a pulse is applied to delay circuit DEL3 forming part of a filter as disclosed in Specification 594,798, to terminate the delay of delay device DEL3, thus bringing the recurrence frequency to which the filter responds into agreement with that of the incoming signal ; the delayed pulses across R8 are applied to switching device SD which is controlled by DEL1 which emits a pulse coincident with the termination of the delay of DEL3. As applied to a responding beacon, the delayed and undelayed signals are applied through a limiting circuit PWL, Fig. 3, to suppressor and control grids of a valve V so that on coincidence a pulse is developed at T2 to operate the beacon. The identifying signal may be used as a synchronizing signal in the system disclosed in Specification 590,067. The delay device DN may be as disclosed in Specification 582,758. Specifications 579,860, 585,347, 588,777 and 590,066 also are referred to.