Page 17 - Royal Observer Corps

AWDREY Detector head

The AWDREY installation consisted of three separate elements: the sensor, the detection unit and
the display cabinet (timer). The sensor was mounted on the roof of the building. The detection unit
installed in a special room that was enclosed inside a Faraday cage; in the case of the Royal
Observer Corps controls, this was the "Radio Room" that already protected the sensitive radio
equipment from the effects of EMP.

During the early phase of operations, a spare observer was required to stand next to the display
unit and monitor it constantly to identify initial responses. Once a nuclear strike on the UK had
been confirmed by the Director UKWMO (or his deputy), readings from AWDREY were ignored
during subsequent nuclear bursts within the attack, and the readings from ROC posts became the
main method of detecting and identifying any subsequent near ground bursts.

The 12 ROC AWDREY units were located at the group controls in Exeter, Oxford, Horsham,
Bristol, Colchester, Carmarthen, Coventry, Carlisle, York, Dundee, Inverness and Belfast. This
siting pattern provided sufficient detectors that the entire UK was covered, but the units were far
enough apart that a lightning storm would be unlikely to trigger simultaneous AWDREY responses
at two sites.