Improvements relating to electrical timing apparatus

745,563. Stencil switches. METROPOLITAN-VICKERS ELECTRICAL CO.. Ltd. July 16, 1954 [July 16, 1953], No. 19785/53. Class 38(5) A switch for producing a series of electric impulses comprises a rotatable record surface provided with a number of indentations at selected intervals along a path on said surface, and a mechanical pick-up device adapted to actuate contacts to produce an impulse each time the pickup meets an indentation. As shown, the pick-up 7 is carried by an arm 8 pivoted and slidable on a rod 5 and having a "half-nut" 13 engaging a lead screw 14 so that the pick-up may be moved radially across the record surface 1, this movement combined with the rotation of the record causing the pickup to move along a spiral path over the record. The indentations are formed by holes 25 and the pick-up has a pointed stylus 18 mounted on a spring 19 supporting a contact-carrying arm 20. The pick-up is supported by a further member resting on the record surface so as to cause relative movement between the stylus and the pick-up when a hole 25 is engaged, silver contacts 21 22 thereby being closed momentarily. The half-nut 13 enables the arm 8 to be raised to free the pick-up from the screw 14 during resetting. The contacts may be normally closed and the pulses may be used to energize an electromagnet ratchet motor to drive a recording chart.