GB822095A - Improvements in computing devices - Google Patents

Abstract

822,095. Circuits employing bi-stable magnetic cores. SPERRY RAND CORPORATION. May 30, 1957, No. 17145/57. Class 40 (9). An exclusive OR gate comprises a core with a power winding 21 energized by a train of pulses in one sense and energized in the other sense by a source of D.C. in the intervals between pulses so as to switch the core to and fro between its remanent saturated states, two input windings, 22 and 23, being such that an input to either inhibits switching of the core in one sense so that the consequent low impedance of the winding 21 causes the generation of an output but the coincidence of inputs produces no inhibition and no output. As shown, an alternating source of square waveform seen at A in Fig. 3 is applied to terminal 24 so that positive half-cycles energize winding 21 over diode D3 and resistor R2 to negative D.C. source- V and, if only magnetizing current flows, this does not appear across R2 due to an equal reverse current from -V to earth over rectifier D4. During half-cycles when terminal 24 is disconnected, the source - V switches the core back over rectifier D4, winding 21 and resistor R1. The input windings comprise the halves 22, 23 of a centre-tapped winding and the sources of input signals are of low impedance and deliver inputs to terminals 26 and 27 coincident with negative half-cycles of the square wave source as seen at B and C, Fig. 3. Either input finds an earth with the other source so that if both inputs are present at once neither input winding is energized. If one input is present the flux due to D.C. source -V in winding 21 is neutralized so that the subsequent positive half-cycle of the square wave source finds low impedance in winding 21 and develops an output across resistor R2 which is extracted over rectifier D5 from terminal 25 as seen at D in Fig. 3.