GB739109A - Improvements in or relating to counting and like circuits - Google Patents

Abstract

739,109. Electronic counting - apparatus. MULLARD RADIO VALVE CO., Ltd. May 11, 1954 [June 26, 1953], No. 17799/53. Class 106 (1). [Also in Group XL (c)] A digital counter comprises a plurality of bi-stable single-transistor stages connected in succession, a plurality of rectifiers each connecting the collector of one stage to the emitter of the succeeding stage, means for conveying input pulses simultaneously to the emitter connections of said stages, and a plurality of collector impedances, one for each stage so arranged that when a particular stage is in the "off" " state the rectifier connecting it to the succeeding stage is biased in its reverse direction, thus preventing input pulses from reaching the said succeeding stage, while when a particular stage is in the " on " condition the increased collector current reduces said biasing sufficiently to permit a pulse to pass the rectifier and trigger the succeeding stage from its " off " to its " on " state. In this way successive input pulses successively trigger each stage from its " off " to its " on " state. Each stage. for example stage 2, consists of a point-contact transistor 11 arranged to have two stable states, an " off " state in which a small negative current flows from the emitter via a diode 13, which serves both to limit the negative voltage on the emitter to - Ee volts and as an emitter load, battery Ee, secondary winding of a transformer T feedback resistance 12 and back to the base of the transistor, and in which a small positive collector current flows, and an " on " state in which relatively large positive currents flow in both the emitter and collector circuits. During the " off " state the emitter potential of each stage is lower than the collector potential, so that the diode (18) connecting two adjacent stages (stages 2 and 3) is biased in its reverse state when both stages are " off " and is in its forward state when the first of the two adjacent stages (stage 2) is " on." Thus if stages 1 and 2 are " on " and the other stages are off a positive input pulse applied to each stage via condensers 6, can only affect stage 3, since that is the only stage having a conducting input diode 18. Successive pulses therefore successively trigger each stage to its " on " condition until the last stage is reached which differs from the preceding stages in that a condenser 103 forms the emitter load and in that the stage has only one stable state, namely " off," and which functions as a pulse regenerator, producing a positive output pulse via a condenser 105 which is fed back, via transformer T, to each preceding stage which is consequentially triggered to its " off " state. In a modification the first stage of the chain is preceded by a diode 08 suitably biased to simulate an imaginary preceding stage in its " on " state, and thus ensuring uniform sensitivity for each stage.