This gyrocompass repeater has a brass bowl that contains an electric motor for driving the compass card. The bowl is set in gimbals and has two lamp-holder fittings on either side and a card adjustment control at the side. The compass card has a diameter of 8 inches (203 mm) and is divided into degrees, with additional figures printed in reverse for the use of a horizon ring with the repeater. There are also markings at the cardinal and half-cardinal points.

The repeater was originally part of a gyrocompass system used on HMS ‘Triumph’, which was decommissioned in 1981. The repeater would have been linked to a master unit, from which the compass reading came. Gyrocompasses were first successfully developed at the beginning of the 20th century as a solution to the problems of magnetic variation and deviation that are inherent in magnetic compasses. They use the properties of spinning gyroscopes which keep the compass pointing in a fixed direction, usually Earth’s true north.