GB1339322A - Analogue transmission system - Google Patents

Abstract

1339322 Analogue measurements MICRO CONSULTANTS Ltd 7 April 1972 [12 Jan 1971] 1489/71 Headings G1N and G1U [Also in Division H4] In an analogue transmission system in which a wanted signal 12 has an interference signal 13 e.g. 50 Hz hum superimposed thereon, the effects of the latter are eliminated by detecting 15 the zero-crossing instants of the interference, and, gating 10 the wanted signal to a receiver only during these instants. The receiver may be an analogue to digital convertor. A plurality of analogue signals may be multi-placed to a single receiver Figs.5, 6 (not shown). The pulse output of the gate may be stored and integrated prior to analysis in the receiver Figs. 11, 13, 14 (not shown). The zero crossing instants may be detected by using a separate interference source whose output is phase synchronised with that of the interference signal Fig.2 (not shown) or by filtering off a portion of the incoming signal Fig.4 (not shown) whereby the interference signal alone is presented to the zero crossing detector. The system is of utility in a remote measuring system wherein a physical variable e.g. temperature, pressure or weight, is monitored electrically and the wires over which the signals are transmitted to a central station are subjected to induced interference from adjacent power circuits.