Y service

Sometimes both functions were operated at the same site, with the direction finding (D/F) hut being a few hundred metres from the main interception building to minimise interference.

The sites collected radio traffic which was then either analysed locally or, if encrypted, passed for processing initially to the Admiralty Room 40 in London and then during World War II to the Government Code and Cypher School at Bletchley Park in Buckinghamshire.

[7] The term was also used for similar stations attached to the India outpost of the Intelligence Corps, the Wireless Experimental Centre (WEC) outside Delhi.

[9] The design of land-based D/F stations preferred by the Allies during the Second World War was the U-Adcock system, where a small operators' hut was surrounded by four 10 ft-high (3.0 m) vertical aerial poles, usually placed at the points of the compass.

Aerial feeders ran underground, surfaced in the centre of the hut and were connected to a direction finding goniometer and a wireless receiver, that allowed the bearing of the signal source to be measured.