Abstract: A charging circuit for a helicopter dipped sonar system in which a single ble conducts sonar and command signals in either direction along with a DC charging current from the helicopter to a storage battery in a submersible sensor unit. A multiplexer and power supply in the helicopter respectively provide simultaneous transmission of command data and charging current over a common conductor to the sensor unit. A filter and demultiplexer positioned in the sensor unit passes only the data for control of a sonar transmitter. The storage battery is charged directly from the conductor and a battery charge indication as well as hydrophone information is combined by a multiplexer at the sensor and returned to the helicopter by the common conductor for data display and power supply control.