An automatic transfer control device for generating signals to cause associated circuit interrupters to selectively energize an electrical distribution system from either of a pair of electrical power sources. The device includes an over- and under-frequency monitoring circuit to determine if the power...http://www.google.fr/patents/US4090090?utm_source=gb-gplus-shareBrevet US4090090 - Automatic transfer control device and frequency monitor
Automatic transfer control device and frequency monitor
