Abstract: A system senses alternating current in a conductor, such as a main line supplying electrical power to a home, and responds to the sensed current as by providing a warning signal when the sensed current exceeds or is less than a preset value for a predetermined short period of time. The current sensor itself is a simple coil of wire, either with an air core or a partial ferromagnetic core, which can be easily operatively associated with the current carrying conductor without the need for disconnecting the conductor from its terminals and which when installed does not present the hazards associated with current transformers.

Abstract: A control for an A.C. motor operates to feed a high average value of voltage to the motor during a starting period of predetermined duration and to then automatically switch the voltage supplied the motor to a lower average voltage of substantially fixed value. This lower value of average voltage is determined without feedback to the control circuit. The control may be designed for use with single phase or multiple phase motors and for motors of various different power ratings.

Abstract: An electronic circuit for de-energizing a lamp or other load after a predetermined period of time uses a gate controlled switch, e.g., thyristor, connected between the load and a source of A.C. voltage. The gate of the thyristor receives control current through a capacitor across which is connected a manual switch. In order to maintain the lamp energized, the switch is closed, bypassing the capacitor, so that uninterrupted gate current flows into the thyristor gate terminal to maintain the thyristor on. The delayed turn-off function is provided by opening the manual switch, whereby the capacitor in the thyristor gate charges up at a rate determined by an RC time constant. The charge build-up on the capacitor decreases the magnitude of gate current until the thyristor turns off due to gate current starvation. Several different embodiments of the circuit are disclosed.