GB621690A - Improvements in or relating to mechanisms for responding to predetermined electricalsignals of morse form - Google Patents

Abstract

621,690. Selectors responsive to code signals. COOPER, A. H. May 10, 1946, No. 14123. [Class 40 (i)] An alarm device responsive only to a particular signal, such as a series of dashes, each of 3¢ to 4¢ seconds duration, separated by spaces of ¢ to 1¢ seconds, comprises a shaft 1 which, in the absence of a signal, oscillates about an initial position under the opposing actions of a spring 4 and a driving ratchet-wheel 2 which co-operates with a power-driven pawl 3 operated several times a second. The shift carries further ratchet-wheels 5, 6 having, respectively, toothed portions 10, 11 corresponding with the maximum lengths of the dashes and spaces of the signal and with which co-operate pawls 7, 8 actuated by an electromagnet 9 energized by the signal, the arrangement being such that when either pawl engages its ratchet-wheel the other is free, whilst in an intermediate position both pawls are free. A correct signal thus causes the pawls 7, 8 alternately to engage their ratchet wheels to allow progressive rotation of the shaft under the action of the driving pawl 3, return of the shaft by the spring 4 being prevented whilst pawls 7, 8 are changing over by a further pawl 17 then engaging one of a number of notches 18 in a holding disc 16'which rotates with the shaft. Release arms 12, 24 adjacent the wheels 5, 6 disengage pawls 7, 8 and allow the shaft to return if the maximum time limit of either a dash or space is exceeded, whilst if the minimum time is not exceeded, the teeth of one or other of the ratchet-wheels are not in a position to be engaged by a pawl when the other pawl disengages, so that the shaft will again return to its initial position. A shutter disc 19 connected to the holding disc 16 through lost motion closes the notches 18 on return movement of the shaft and so prevents pawl 17 from engaging. After a predetermined angle of rotation of the shaft by a correct signal, a striker 25 closes an alarm or like circuit. Switches 14, 15 and 22, 23 operated respectively by relative movement between release arms 24 and wheel 6 and between the holding and shutter discs may be arranged to cause the release of all pawls. The device may be used as a transmitter by moving a pawl 27 into engagement with a ratchet 26 so that the shaft rotates continuously and drives a cam 28 operating keying contacts 29.