Abstract: A solenoid driver circuit adapted for use with a digital magnetic latching olenoid which has first and second solenoid coils. The solenoid driver circuit includes a bridge circuit which receives a logic signal and first and second pulse signals. The solenoid driver circuit also includes a voltage source which provides a direct current and first and second resistors respectively connected to the first and second solenoid coils. The bridge circuit, responsive to the logic signal and the first pulse signal, provides a first current path from the voltage source through the first solenoid coil and the first resistor to ground and a second current path from the direct current voltage source through the second solenoid coil to ground.

Abstract: An underwater speaker system having a pressure equalization system enabling the speaker to operate in its intended fashion over a wide range of water depths, e.g. from two feet up to sixty feet. Water pressure is applied to a diaphragm that forms one wall of a variable volume an internal face of a speaker membrane. Pressures are equalized on opposite faces of the membrane to enhance speaker performance.