Abstract: An overflow prevention mechanism for use in association with liquid transfer systems of the type including an electrically controllable flow control device such as a pump connected between a source of liquid and a liquid tank, the mechanism including a backup liquid level sensor and a shunt trip breaker or other normally-closed switching device. The backup liquid level sensor senses if the level of liquid within the tank reaches an extreme high level. When the liquid level within the tank reaches the extreme high level the backup liquid level sensor produces an output indicative of the liquid having reached such extreme high level. The shunt trip breaker is connected between the source of electrical energy and the flow control device.

Abstract: An annunciator control circuit adaptable for responding to a plurality of types of fault indicative inputs is provided. The control circuit includes a signal conditioning circuit portion having an input line and an output line. The signal conditioning circuit also includes switch means adjustable for selectively configuring the signal conditioning circuit portion to receive each of the plurality of types of fault indicative inputs at the input line thereof and to provide a conditioned fault indicative output signal in response thereto at the output line. The control circuit further includes a first latching circuit portion connected to the output line of the signal conditioning circuit portion and having a first output line. A first switching transistor of the control circuit includes a base, collector, and emitter, the base connected to the first output line of the first latching circuit portion.