Air raid sirens first sounded the warning in London in September 1939 shortly after the outbreak of war with Germany. During the May Blitz of 1941, the frightening sound of the air raid siren could be heard across Liverpool several times each day.
The “Carter” air raid siren, manufactured by Gents of Leicestershire was used exclusively in Britain throughout World War II. The sirens made a very loud and long signal or warning sound. For an alert, the siren sound pitch rose and fell alternately, whereas the “All Clear” was a continuous sound from the siren.
When people heard the siren they would stop what they were doing and make for shelter. Shelters varied from underground stations, to smaller prefabricated Anderson and Morrison shelters. If the bombing seemed light, many people preferred to stay in their homes under the stairs. Government warning messages describing how best to react if the siren sounds, were broadcasted to the general public over the wireless and at the pictures.
Volunteer air raid precaution (ARP) wardens would protect civilians from the danger of air-raids as much as possible during a bomb attack; directing people to the nearest shelter and using their knowledge of the local area to help find and reunite family members who had been separated in the mad rush to escape the bombing.