Improvements in circuit-arrangements for use in automatic signalling systems for testing a voltage or a resistance in an outlet of a switch

摘要

660,521. Electric control systems. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Sept. 9, 1949. [Sept 13, 1948] No. 33376/49. Class 40 (i). [Also in Group XXXIX] In a system in which tests are made over a wiper of a switch to determine the voltage or resistance connected to a co-operating terminal, a current due to a condenser charge or discharge is caused to flow across the point of contact prior to the making of the test. This current which is higher than that used in making the test is used to break down the resistance due to the formation of oxides on the contacts. In the embodiment shown in Fig. 1 in which the device 17 is operated to stop the switch KS when the potential encountered in its bank is equal to that connected up by a numerically set switch MS the condenser 18 produces the necessary discharge current when the wiper passes (e.g.) from terminal 10 to the adjacent terminal 11 having a different potential. The effect may be enhanced by additional condensers 19. Fig. 2 illustrates a circuit for determining the potential connected to an outlet on which the switch EK has been stopped by means unspecified. When the test is to be made contact 25 connects up the voltage comparison device SO and condenser 22 discharges into condenser 24 over the wipers of the intervening switches.