Oscillator type number 37, probably used no earlier than 1941, as a signal source to test the Chain Home receivers.

This is a rare example of equipment used to test operation of the Chain Home radar system. It acted as a signal source for the Chain Home receivers. Chain Home was the word's first early warning radar system. It was developed by Robert Watson-Watt and Arnold Wilkins between 1934 and 1937. The Royal Air Force began construction of five early warning radar stations in 1937 and they were operational by 1938. The development of the Chain Home system was integral to British success in the Battle of Britain in 1940. The electronic valves in this oscillator suggest it being used no earlier than 1941.