Braun Aktiengesellschaft

Peter Busch

Lothar Pacher

Horst Schaefer

Harald Hoffman

Dan C Raducanu

Electronic clocks with analog time displays and a vibrating quartz crystal (1) as a time standard, as well as electronic frequency dividers (6, 7). The display elements are driven by an electronically controlled motor (SM), said motor comprising a power winding (87) and a control winding (68). The control and regulating circuit for the electronically controlled motor (SM) is so designed that only one rpm above the rated rpm is controllably adjustable and, when the frequency of the clock varies, correcting signals are supplied to the AC drive pulses in power winding (87) through a bistable flip-flop (50), said flip-flop being subjected to real pulses derived from frequency dividers (6,7) and pulses derived from motor (SM), a NOR element (58) connected to the output of flip-flop (50) and an additional frequency divider (59), a field effect transistor (88), and a resistor (89). These correction signals increase the amplitude of the electrical drive signal, applied to power winding (87), and accelerate motor (SM) to the maximum set rpm. The invention can be used in time-keeping devices, especially quartz-controlled clocks, with maximally constant frequency.

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Fenin, Switzerland

Peter Busch