He organised the night fighting units into a chain known to the British as the Kammhuber Line, in which a series of radar stations with overlapping coverage. The stations were layered three deep from Denmark to the middle of France, each covering a zone about long (north-south) and wide (east-west). Each control centre was known as a "Himmelbett" (four-poster bed) zone, consisting of a Freya radar with a range of about , a number of searchlights spread through the cell, and one primary and one backup night fighter assigned to the cell. Royal Air Force (RAF) bombers flying into Germany or France would have to cross the line at some point and the radar would direct a searchlight to illuminate the aircraft. Once this had happened, other manually controlled searchlights would also pick up the aeroplane and the night fighter would be directed to intercept the illuminated bomber. Demands by "Bürgermeister"s in Germany led to the recall of the searchlights to the major cities.