A new high-speed digital technique for computer use

A new method is described for realizing logical functions using square-loop ferrite cores and transistors. Complex circuits can be built up from identical elements, each consisting of one core, one transistor, three diodes and one resistor. The technique differs from earlier methods in that the current required to set a core to the `1¿ state is derived from a common supply and not from a previous stage. The control of digit transfer between stages is effected by a transistor whose collector and emitter are connected across one winding of the core. When a `1¿ is to be set in the core, the transistor is arranged to appear as an open-circuit, in which condition flux reversal is possible; when a `0¿ is to be set, the transistor appears as a short-circuit preventing reversal of flux. The core is reset to `0¿ at a controlled rate, producing a standardized voltage across the output windings. Logical operations are carried out by the analogue addition of these voltages. The system requires only two low-voltage d.c. supplies and is tolerant of voltage and component variations. It operates reliably at digit rates of 500kc/s. The paper also describes an experimental application of the method, designed to test its performance.