GB178957A - Improvements in and relating to delay action devices employing thermionic valves - Google Patents

Abstract

178,957. Lea, N., and Radio Communication Co., Ltd. Jan. 29, 1921. Thermionic relays. - Relates to delaying or retarding arrangements, particularly for the reception of signals, and consists in utilizing as the delay period the time taken in charging or discharging a condenser through a resistance. The condenser is preferably arranged in the grid circuit of a thermionic valve, and the prime movement connects the condenser to a resistance, the final switch being operated by a coil in the plate circuit of the valve. As shown, the condenser C is charged by the battery B, whenever the arm T rests on the spacing-contact S, and the grid G of the valve V is thus kept at a negative potential and no current passes in the plate circuit. An incoming signal moves the arm T to the marking-contact M and connects the grid G and the upper plate of 'the condenser C through a high resistance R1 to a positive point on a battery B2. After a limited time, the potential of the grid G reaches a critical value such that sufficient current is allowed to pass through the valve to operate the relay 0 and to close the output circuit of the contact W. The critical grid potential should be near the middle of the rising grid-potential plate-current characteristic, and this critical grid potential should be attained before the charge on the grid G and condenser C have approached too nearly to their ultimate values. When the arm T moves back to the contact S, the grid is immediately charged negatively and cuts off the current through the relay O. A low resistance R2 prevents sparking at the contact S.