GB220945A - Improvements in or relating to electric alarm devices - Google Patents

Abstract

220,945. Geffcken, R. H. H., and Richter, R. H. Aug. 23, 1923, [Convention date]. Thermionic relays and generators; light and heat radiations, control of apparatus by.--Electric discharge tubes are so arranged in connection with burglary, theft, or fire alarms that, when the alarm is to be given an alteration occurs in the direct current flowing through a resistance, thus changing the potential difference between the electrodes and causing a considerable alteration in the discharge current. In the arrangement shown in Fig. 1, the electrodes 2, 4 of a three-electrode valve 1 are connected to a direct or alternating current source, and the three electrodes 2, 3, 4 are suitably connected to an oscillatory circuit 5 for the production of oscillations therein. Between the grid 3 and filament 2 is connected a potassium cell 6 with series and shunt resistances so proportioned that under normal conditions the valve is just not oscillating. The alarm is given when the cell 6 is exposed to light, which causes the negative potential on the grid 3 to be reduced, so permitting the valve to oscillate. The sudden alteration of the supply current operates a signalreleasing device 7; or an incandescent lamp associated with the circuit 5 ma.y be lit. Fig. 2 shows the use of a glow discharge lamp 8 connected to a supply source 9, 10 through a signal-release device 14 and resistance 11, the supply lead 10 being earthed. In shunt to the lamp are a resistance 13 and the extended alarm wire 12. The voltage across the lamp is insufficient to produce a glow discharge, until the wire 12 is cut or earthed. The signal may be given by the device 14, or by the lamp itself. The Specification as open to inspection under Sect. 91 (3) (a) states that if alternating current supply is used, the discharge tube is arranged to have different glow voltages for the two directions of the applied voltage, or to pass different discharge currents in the two directions, so that a rectifying action occurs, and a direct current, relay may be used! for releasing the signal. Combined A.C. and D.C. voltage may be applied to the lamp, so as to maintain a discharge when once set up. This subject-matter does not appear in the Specification as accepted.