This is an early model of a marine radar that was installed in the merchant vessel SS 'Birdwood' in 1949. It consists of a display unit on a pedestal mounting. The display screen is 5 inches (127 mm) in diameter and has a degree scale around the edge with a rotating plastic cover with a bearing line inscribed on it.

Radars make use of very high frequency radio waves transmitted from a rotating scanner mounted high on the ship. If the radio waves strike a solid object or rain storm, they are bounced back to the scanner, interpreted, and the output displayed on a screen on the bridge.

Radars were developed in Britain and the USA during the Second World War. At sea they could be used for position finding and to give warning of approaching ships or hazards. The name was taken from the letters in the phrase from 'Radio Detection and Ranging'.