© The Institution of Electrical Engineers
The paper describes a ferrite-core unit serving both as memory and line scanner in a 64-subscriber electronic telephone exchange used as a p.a.x. (private automatic exchange). This dual function is realised by ferrite cores with a rectangular hysteresis loop, using working points different from those of conventional computer core memories and determined by m.m.f.s produced by currents in the appropriate windings. The cores are arranged in a square matrix and are scanned by a ‘linear-selection’ mode. A special bridge amplifier, with logic-controlled switches in its four arms and the reading winding at its centre, permits the reading currents to be directed as required by actuating a pair of opposite arms.
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http://iet.metastore.ingenta.com/content/journals/10.1049/piee.1970.0372
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