The air raid warning system was developed in 1938/9. The sound of the 'warning' signal and the 'all clear' would become very familiar to people living in large cities in Britain.
Air raid sirens were placed on the top of tall buildings - often police stations or similar - or on the top of poles if no suitable building could be found.
In cities the sirens were powered electrically and produced two signals.
The first was the warning - a rising and falling signal, created by varying the power to the siren.
The second was the all clear - a single, continuous note. After it was confirmed the skies were clear of enemy aircraft the 'all clear' would sound. It brought relief to countless thousands as they made their way wearily out of shelters to resume daily life.
A collection of programmes to download as mp3 files at any time. Includes dance and music.
See all School Radio and other Learning podcasts available from the BBC Podcast Directory.
Enjoy our new collection of Beatrix Potter's well-known tales retold by an all-star cast for a young audience.
Get to grips with life’s big questions with our new series ‘Just Think…’
We welcome your feedback, suggestions and pupils' work.
Commemorate the outbreak of WW1 by staging our specially-written play 'Archie Dobson's War'.
All 13 episodes of Michael Morpurgo's moving WW1 story are available to listen to online.
Notes to support the programmes. For Autumn 2014 onwards Notes are on individual series pages.