GB583894A - Pulse modulation systems - Google Patents

Abstract

583,894. Pulse modulation. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation). Feb. 15, 1944, No. 2772. [Class 40 (v)] In a pulse-modulation receiver, interference is reduced by the use of a gating valve which opens up the detector to each received signal pulse, the gating pulse being slightly wider than the signal pulse and derived through a delay network from a preceding signal pulse. The signal derived from a radio receiver 20 and limiter 24 takes the form of pairs of short pulses 1, 2 ; 3, 4 ; &c., as in Specification 579,777, the interval a between each pair being variable with the modulation. The pulses are applied directly to a demodulator 35 which is normally biased prohibitively by a source 36. The pulses are also applied through an amplifier 32 to a delay network 33 from which emerge wider pulses 13, 14 delayed by a period equal to the mean interval c between corresponding components 1, 3 or 2, 4 of consecutive pairs. The pulses 13, 14 pass through a limiting amplifier and are fed as wider pulses 15, 16 to open up the gating valve in the demodulator 35. These gating pulses coincido with and overlap slightly the following pair 3, 4 of signal pulses, so that interference such as 23, 26 occurring between the pulses is not admitted to the demodulator. Specification 511,222 (as open to inspection under Sect. 91) is referred to.