GB553845A - Slow-operated electrical circuit - Google Patents

Abstract

553,845. Electricity supply; thermionic valve relay circuits. STANDARD TELEPHONES & CABLES, Ltd. March 27, 1942, No. 4074. Convention date, Oct. 23, 1940. [Class 38 (iv)] [Also in Group XL] Condenser arrangements; switching control.- An electrical circuit is rendered operable after a time interval, e.g. of the order of minutes, by the slow charging of a condenser c by alternate short impulses from a saturable transformer 2 producing a peaky wave having a slow build up and a rapid rate of decay. The primary winding is connected through an inductance 3 and resistance 4 to an A.C. source 1 of usual frequency and the secondary is connected in series with the condenser and the unidirectional main gap of a cold cathode gas filled discharge tube 7 through a resistance 8. An auxiliary gap is connected through a resistance 6 in series with a portion of the secondary winding, which is shunted by a copper-oxide rectifier 5 so that the tube is responsive only to alternate half waves and the voltage range over which the tube 7 is rendered conductive is increased. The peaky secondary voltage breaks down the auxiliary gap late in the half cycle whereupon a short charging impulse passes through the main gap to the condenser C. In one application, a circuit 10, intended to indicate when a relay 11 does not operate within a time determined by the aforesaid circuit, an enabling relay 15 closes, when the time has elapsed and the relay 11 has not operated, due to the discharging of the condenser C over the auxiliary gap of a second gas filled, cold cathode tube 13, whereupon a battery 14 passes current through the main gap and the relay 15. When the relay 11 operates a relay 17 short-circuits the condenser and resets the apparatus.