Early warning

During the first world war there were a number of air attacks made upon the North-East coast by German aircraft. Zeppelins raided the area fifteen times between April 1915 and November 1917.

Defence against these raids was very limited and depended on knowing when aircraft were approaching and from what direction. To this end a series of listening stations were erected along the coast (and also in the south of England) in the form of 'sound mirrors'. This example, now sitting in the midst of a Redcar housing estate, and listed Grade II, was constructed by the Royal Engineers in 1916. It is about 17ft high.

The sound of the approaching aircraft was reflected off the concave surface and into a receiving trumpet mounted on a steel column in front. This was connected to the listening operator by a stethoscope and this was moved to find the part of the dish producing the most sound, which indicated the direction of approach. At least the local populace could then be given advanced warning of the impending raid.

Acoustic listening devices of various shapes were constructed along the coasts until the 1930s after which they began to be replaced by Radar.