with provision for a number of operations at different times, e.g. ringing the bells in a school

Full Title

Producing acoustic time signals by electrical means > producing the signals at adjustable fixed times > with provision for a number of operations at different times, e.g. ringing the bells in a school

Child Classifications

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• G04C 21/305
• G04C 21/32 giving indications at a number of places each at a different time, e.g. system of alarms in a hotel