Current meter - underwater indicator

Box containing underwater indicator of a current meter, length of rope marked at approximately 1 metre intervals, and two plastic boxes filled with small parts. This is a Kelvin Hughes Direct Reading Current Meter (DRCM) which works in conjunction with NAV1761. A streamlined underwater unit with conical mesh tail aligns itself so that it heads toward the stream. It contains a fluxgate system, which sends up the wire signals that are resolved in the indicator unit (NAV1761) when a setting is made so that the angle between the direction of flow and the local magnetic meridian can be read of a circle. A four bladed propeller operates contacts, which send up the wire pulses whose frequency depends upon the water speed. A circuit in the indicator unit converts this pulse frequency into a voltage that shows on a meter, which is calibrated directly in water speed. So the DRCM shows on one dial the water speed and, after a setting operation, the direction of flow (magnetic) on another dial.