Abstract: A system for sensing the phase of a three-phase AC system and detecting phase reversal and undervoltage and phase unbalance and for providing a switching function when the system is not functioning properly.

Abstract: A machine tool timing relay has immunity from electrical noise on a control signal, and has an oscillator capable of generating pulses having a predetermined frequency, a means for adjusting the predetermined frequency over a continuous range of frequencies, a counter capable of counting the pulses and capable of generating an output signal after a predetermined number of the pulses are counted, means responsive to a start signal for initiating the counter to count the pulses, an optical isolator circuit responsive to the control signal for generating a light, detecting the light, and generating the start signal in response to detecting the light in order to isolate the counter from electrical noise mixed with the control signal, an electrical contact, and an output circuit responsive to the output signal for operating the electrical contact when the counter generates the output signal so that the contact is operated after the counter counts a predetermined number of the pulses.

Abstract: A repeat cycle delay timer in which the on-delay and off-delay periods are individually selectable by individual adjustment of two pulse oscillators respectively associated therewith. The pulses are alternately applied to a pulse counter which produces an output signal after a preselected number of pulses have been counted for that period. The counter then counts pulses from the other oscillator until the end of the other delay period. Different counter outputs may also be selected to produce simultaneous adjustment of both the on-delay and the off-delay periods.