Chain Home
Chain Home was the name for the original early warning radar system put in place in England. Chain Home equipment was also called AMES Type 1, which was short for Air Ministry Experimental Station. These stations were located along the east and south coasts of England.
The Chain Home system was developed when researchers discovered that aircraft reflected short wave radio signals and that these reflections could be detected by Chain Home equipment. Research and development was led by Dr. Robert Watson-Watt beginning in 1935, and by 1939 radar stations making up the Chain Home system were in place.
The Chain Home system had a detection range of about 210km in distance and about 3000 feet (0.9km) in height. Radio signals with a 12 meter wavelength would be sent out through a transmitter and signals reflected off of incoming aircraft would be picked up by a receiver. The receiver would then display the signal on a cathode raid tube. An experienced radar operator would be able to interpret that signal and determine the number of incoming aircraft, how far away they were, and in what direction they were heading.