GB602267A - Electronic trigger circuit - Google Patents

Abstract

602,267. Valve generating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 25, 1945, No. 19114. Convention date, June 30, 1943. [Class 40 (vi)] An electronic trigger circuit comprising two valves has one stable and one unstable state of operation and means for applying pulses to the cathode of one of the valves. Fig. 2 shows a multivibrator circuit, valve V1 being non- conducting and valve V2 conducting, in the stable state. A resistance RK1, which may be of high value, is shunted by a rectifier such as diode DI, and connected between the cathode of valve V1 and earth. Valve V1 may be rendered conducting by the application of a negative pulse to the cathode of valve V1 through condenser C, sufficient to overcome the negative grid bias, and normal multivibrator action follows whereby valve V2 is cut-off. The unstable state with valve V1 conducting and valve V2 non-conducting, continues until after a period determined by the time constant of the condenser CH2 and resistor RD2. When valve V1 starts to conduct, a positive voltage is developed across resistor RK1 and diode D1 then starts to conduct, which has the effect of considerably reducing the time constant of the circuit elements associated with condenser C. Thus the duration of the unstable condition of the circuit depends only on the circuit elements CH2, RD2, and may be made independent of the duration or shape of the input pulse, provided only that the duration of the input pulse is shorter than that of the desired output pulse. By this means, rectangular pulses of short duration, of the order of five microseconds, may be produced. The valves V1 and V2 may be in one envelope. The invention may also be used to provide a high impedance tripping or synchronising input circuit by arranging for the resistance shunting diode D1 to be of high value.