The civilian spy network was formed before the wireless network came into being. Initially it was set up as part of the Section D Home Defence Organisation. This was a network of observers, linked by runners, whose role was transport messages across the front line, after an invasion, to reach the British commanders. However, it became clear that in practice this would take far to long for the messages to be useful, resulting in the setting up of the wireless network, possibly in 1941 into 1942. The spy network was modified to transport messages to the wireless operators instead.
Each wireless station had in the region of 20 to 30 people involved in supplying messages. Some would be observers who would produce the intelligence. They were provided with materials to allow them to identify German units and equipment. Some were runners, who would carry the messages between dead letter drops. These were locations where a message could be concealed for another runner to collect, without the two ever meeting in person. A wide range of different dead letter drops were used. These included hollow tree stumps, behind ID pates on telegraph poles, hidden within gateposts and many other places. This was designed to avoid the whole network being compromised if one person was captured. Unlike the Operational Branch, the Special Duties civilians were both men and women. Women were felt less likely to be stopped and searched by the occupiers. It seems a number were widows of servicemen or whose husbands were serving overseas
The network would cover an area of around 10 miles around each wireless station. A Key Man was in charge of this network and documents indicate that the Key Man was a wireless operator.
A Group Leader was in charge of the civilian staff over a much wider area, possibly even the whole network. Unlike the Operational side of Auxiliary Units, very few of these Group Leaders and Key Men are known. Even fewer of the Observers and Runners can be confirmed.