It has always been important to be able to measure the depth of water below a ship, but it was not until the 20th century that automated systems for doing this became available with the development of the echo sounder, which measures depth by timing the echo from a sound source.

Initially, echo sounders used paper readouts to record the results, as does this example made by Kelvin Hughes, one of the leading manufacturers of navigational instruments in the UK. The machine comprises of a recording unit, a power unit, a tachometer (revolutions per minute of the drive shaft), a fix marker switch (not acquired) and a transceiver, which transmits and receives the signal used to detrmine the depth. This particular model was designed for survey purposes and so is adpatable for use in small boats and on a wide range of power supplies. It has a maximum range of 540 feet.

The equipment was given to the museum by Dover Harbour Board.