Abstract: Apparatus for electrically isolating a DC voltage source while the voltage f the source is being measured or otherwise monitored. An electronic switch is provided for selectively coupling the apparatus to the source, and a first optical device coupled to the switch receives a control signal which directs switch operation. The first optical device electrically isolates the switch from electrical equipment which generates the control signal. A device for generating an internal voltage data signal is also coupled to the switch, the frequency of such signal varying according to the voltage of the source. A second optical device receives the internal data signal, and couples an external data signal to voltage monitoring equipment, the external data signal having a frequency which varies according to the frequency of the internal data signal, the second optical device electrically isolating the switch from the voltage monitoring equipment.

Abstract: A pressure insensitive counter for a towed array deployed underwater provs accurate readings of the deployment of the array from a winch. Several magnets are carried on the side of a fairlead sheeve to actuate associated reed switches as the magnets pass by them. The reed switches are oriented with respect to one another to provide binary coded decimal (BCD) signals which are fed to an electronic counter circuit carried inside of a pressurized hull. Mounting the reed switches inside of fluid filled conduits assures that the BCD signals are generated reliably. The electronic counter circuit assures a positive indication of how much of the array has been deployed.