Dowding system

The Dowding system was the world's first wide-area ground-controlled interception network, controlling the airspace across the United Kingdom from northern Scotland to the southern coast of England. It used a complex dedicated buried land-line telephone network to rapidly collect information from Chain Home (CH) radar stations and the Royal Observer Corps (ROC) to direct defensive interceptor aircraft and anti-aircraft artillery. The system was built by the Royal Air Force just before the start of World War II, and proved decisive in the Battle of Britain.

The Dowding system was developed after tests demonstrated problems relaying information to the fighters before it was out of date. Air Chief Marshal Hugh Dowding, commander of RAF Fighter Command, solved the problem through the use of hierarchical reporting chains. Information was sent to Fighter Command Headquarters (FCHQ) central filter room at Bentley Priory and used to prepare a map of the battle. Details of the map were then relayed to the Group and Sector headquarters, where operators re-created the map at a scale covering their area of operations. Looking at the maps, commanders could make decisions on how to employ their forces quickly and without clutter. Instructions were relayed to the pilots only from the squadron's sector control rooms, normally co-located at the fighter's operating bases.