GB966706A - Improvements in or relating to electrical circuit arrangements - Google Patents

Abstract

966,706. Transistor pulse circuits. POSTMASTER GENERAL. Nov. 24, 1960 [Aug. 24, 1959], No. 28923/59. Heading H3T. In a circuit comprising a number of trigger circuit devices T1-T5, Fig. 4 (Prov.), each having two stable states in which transistors TX1 or TX2 or their counterparts in other devices are respectively rendered conductive in response to respective inputs on leads C1 and C2 or their counterparts, the devices are grouped in stages T1, T3, T5, T2, T4 and the input leads to each device T1 in one stage, except the last, are joined through isolating " or " gates, X1 X2 to one input C12 of a trigger device T2 in a succeeding stage. A -VE pulse on terminal C1 thus renders conductive transistor TX2 and its counterparts in T2 and T4 and series connected transistors TX3, TX5, TX6; transistor TX4 and its counterparts being inhibited whereby earth at terminal AL is applied over the series connected transistors to an output terminal A1. If a number of inputs appear on different input leads simultaneously, one path from earth to an output terminal corresponding to one of the inputs is arbitrarily set up and the output (earth) is arranged to effect a selection, and clear the input which made it. A second path corresponding to one of the remaining inputs is then set up, and so on. The trigger circuit arrangement may be biased in favour of an input to a particular one of its terminals and the application of bias may be controlled by a negative switching-on potential being applied to a further transistor connected between the emitter and earth of a trigger transistor, Fig. 3 (not shown). The trigger devices may comprise N-P-N or P-N-P transistors or may be electromechanical relays or electronic tubes. Biasing arrangements may enable coincident signals to be cleared from the right or the left. An alternative arrangement in which some of the triggers are replaced by a three-position trigger is described with reference to Fig. 2 (not shown). The earth connection may be permanent or through a switch K which may be automatically operated in conjunction with the actuation of the final trigger circuit, and in a modified arrangement described with reference to Fig. 1 (not shown), the outputs from three stages of trigger devices are supplied to their respective output terminals A via a corresponding number of " AND " gates.