GL Mk.1 radar receiver, 1939

Gun Laying (GL) Mk. 1 radar receiver was an early example of the series of radar receivers developed by Metropolitan Vickers Limited, and the staff of Bawdsey Research Station in 1938/1939 and was one of the first commercially made radar receivers ever produced. Other closely similar receivers were the later Marks of GL receivers, the MB series, and the Chain Home Low (CHL) series. GL Mk. 1 was an early warning and fire control continuous tracking radar system. This example dates from 1939 but it was in use from August 1939 to April 1941 when it was replaced by GL2. Approximately 400 GL Mk.1 radar transmitters were produced.

The GL transmitters and the corresponding receivers were primarily designed to facilitate anti-aircraft gun-laying by accurately determining the range and bearing of enemy aircraft. They were required to indicate rang within about 50 yards (46 metres) up to ranges of 14,000 yards (12.8km).