Abstract :
Circuit elements are described which have been designed for operation at 100 kc/s to perform logical functions associated with a magnetic-drum storage and data-handling system. Several types of p-n-p alloy-junction transistor are utilized, and both the saturated and unsaturated modes of operation are used. The majority of the transistors have a defined minimum current gain of 10 in the common-emitter configuration and an ¿ cut-off frequency of 3 Mc/s. Techniques designed to minimize the hole-storage effect,1 resulting from oversaturation caused by the non-selection of transistors, have been incorporated in the circuits, and simple rules governing the interconnections between separate logic units have been established. The circuits discussed are reading and writing amplifiers, track-switching circuits, bistable elements, buffer amplifiers, emitter-followers and transistor and diode gates. Individual circuit-elements are contained on standard-sized printed cards, each forming compact plug-in unit assemblies. The interference generated by fault conditions and changes in logic state between groups of circuit elements comprising a specific logic function is minimized by the introduction of filter circuits and the distribution arrangements of the power supplies.
