Abstract: Leakage from a gasoline storage tank or other receptacle is detected by differentiating the output from a liquid-level monitoring transmitter with stepped voltage output and applying the differentiated transmitter signal through an amplifier to a latch controlled relay for activating an alarm. An interlock circuit is provided for deenergizing the detector part of the system whenever the contents of the tank is being altered intentionally.

Abstract: The invention is a time variable thermostatic device adapted for direct connection into a low voltage, two-wire, alternating current control circuit of a heating or cooling unit arranged to vary the temperature set point of a thermostat at selected times to control the operation of the heating or cooling unit. Circuit means including a transformer having primary and secondary windings interconnect in the two-wire control circuit a thermostat having a thermostatic switch, a starting relay or gas valve actuator and a timing means having a timing means that is a multiple of the frequency of the AC voltage in the control circuit together with mechanical means for changing the temperature set point at the desired time of day. The circuit permits actuation of the starting relay and operation of the heating or cooling unit only when the thermostatic switch is closed.

Abstract: A driver circuit for a step motor includes a binary divider circuit for generating pulse outputs of decreasing frequency which are applied to inputs of a logic circuit to generate a output pulses of a predetermined width and frequency. The logic circuit is provided with facilities for selecting the width of the pulses from a plurality of selected widths.