The blackout in Great Britain began on September 1st 1939, two days before the outbreak of war. It was to prevent enemy aircraft finding their targets at night.The rules were very strict, no chinks of lights, no see through curtains, no glowing cigarette ends. Car headlights were dimmed as were street lights. As a result the immediate effects were more pedestrian accidents, and more crimes committed.
One of the most important jobs of the Air Raid Warden was to patrol his area and make sure there were no tell tale lights.
Probably the first thing most people heard after Chamberlain's famous speech on the outbreak of war in September 1939 was the air raid siren. This was an essential piece of kit used to warn both the military and civilians of the threat of enemy aircraft and bombing.Two tones were used; Red Alert which meant imminent attack and the All Clear which meant it was safe to leave your shelter (if you were lucky enough to have one/find one).
The only information about who manufactured them is on this page about the blitz in Liverpool: Liverpool Blitz - the sound of the air raid siren. It says that Gents of Leicestershire made the sirens that were used in Britain throughout the war. Below is an excellent extract from a 1939 film, The Warning, courtesy of BFI.
