GB577345A - Device for the automatic delayed switching on or off of an amplifier or detector - Google Patents

Abstract

577,345. Valve circuits for wireless reception. WEIGHTON, D., and PYE, Ltd. Nov. 15, 1940, No. 16523. [Class 40 (v)] Delayed switching is obtained in a thermionic valve circuit by using a valve with two collector electrodes connected to a positive source and a controlling electrode connected by a condenser to one of the collector electrodes and to the cathode through a resistance. The Figure shows a pentode with the suppressor grid 15 used as the controlling electrode and coupled to the screen through condenser 3. In this way the condenser 3 is charged to the potential of the high tension source while the cathode is cold and after the cathode is operative the valve is inoperative until the condenser has discharged through resistance 4. As shown the rise of anode current will occur suddenly and the grid 15 become positive and draw electron current to discharge condenser so that the grid becomes negative and again renders the valve inoperative. The operative period will depend upon the value of resistance 5. If resistance 4 is returned to a potentiometer across the high tension source delayed switching without the subsequent -reversion to an inoperative condition may be obtained. With this arrangement adjustment of the potentiometer will give a further control of the time period. The valve may be one already existing in the apparatus and may be a high or low frequency amplifier or a detector which may constitute the only valve in the receiver. Impulses may be taken across resistance 7 for the switching of further apparatus.