GB543799A - Improvements in electromagnetic relays - Google Patents

Abstract

543,799. Electric signalling systems. GENERAL ELECTRIC CO., Ltd., and SMART, N. C. Feb. 21, 1941, No. 2362. [Class 40 (i)] Apparatus for opening and closing a pair of contacts 10 in response to pre-determined code signals comprises a self-starting synchronous motor 1 which is unlatched by an initial impulse and runs through a half-revolution provided the subsequent impulses arrive at the proper times, the contacts being controlled by a cam 9. The action is governed by a cam-wheel 4 having two sets of teeth 12-20 and 32-47 for co-operation with the latching member 11 which is moved away from the cam-shaft at each impulse by a vibrating reed 28 tuned to the signalling frequency and controlled by the impulse-receiving magnet 24, 25. In the absence of signals, the motor, which is conveniently of the kind used in electric clocks, oscillates between narrow limits imposed by the engagement of the member 11 with the tooth 12 or 15 and that of a detent 21 with a notch 22 or 23 in the periphery of the cam-wheel. After the motor is released by the withdrawal of the member 11 at the first impulse, if the subsequent impulses do not conform to the pre-determiried code, the rotation is stopped by the engagement of the member 11 with a tooth of one set or the other, whereupon the motor reverses and returns to its starting position. By the provision of other reeds, and latching members for co-operation with further sets of cam-teeth, the apparatus may be made responsive to code signals comprising impulses of different frequencies.