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  • Publication Date: December 31, 1969
  • Publication Number: GB-1054058-A

Abstract

1,054,058. Transistor pulse circuits. STANDARD TELEPHONES & CABLES Ltd. Oct. 18, 1963 [Oct. 25, 1962], No. 41244/63. Headings H3T and H4L. In equipment, such as a transponder, in which the arrival of incoming pulses in excess of a predetermined rate could cause the equipment to function incorrectly, incoming pulses are applied via an input transistor to a diodepump pulse-rate measuring circuit which when the mean pulse rate exceeds a predetermined value periodically triggers a monostable circuit which then delivers a pulse of predetermined duration to gate the input transistor off for the duration of said pulse, so that the overall mean repetition rate of the pulses appearing at the output of the input transistor is reduced to a value at which the equipment can function correctly. Incoming negative pulses are applied to the base of a transistor Q1, output pulses being taken from its emitter. Pulses are also applied from the emitter to a diode-pump circuit comprising diodes CR1, CR2 and capacitors C1, C2, the capacitor C2 being continuously discharged through a resistor R5, so that when the repetition rate of the pulses applied thereto exceeds a limiting value (e.g. 750 p.p.s.) the potential developed across the capacitor builds up to a sufficient value to cause the breakdown of unijunction transistor Q2 so developing a positive pulse across resistor R7. The limiting value of repetition rate may be adjusted by potentiometer R3. Resistor R6 in the base-two circuit of the unijunction transistor Q2 provides temperature compensation therefor. The pulse developed across resistor R7 triggers a monostable circuit comprising reciprocally-coupled transistors Q3, Q4 which delivers a positive pulse of 15 milliseconds duration from the collector of transistor Q4 to the base of a gating transistor Q5 which thereupon conducts to short-circuit the input to transistor Q1. The greater the repetition rate of the incoming pulses the shorter will be the time taken by capacitor C2 to build up a sufficient voltage to cause the unijunction transistor to break down, so that the frequency with which transistor Q5 short-circuits the input will increase as the input repetition rate increases and the means rate at which pulses are applied to the output line will not exceed a predetermined limiting value. .

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