air defence networks during the early 1930s. For example, the British deployed the CHAIN HOME system; the French used a bistatic Continuous Wave (CW) radar in a "fence" (or "barrier") system; the Soviet Union deployed a bistatic CW system called the RUS-1, and the Japanese developed a bistatic CW radar called "Type A". The Germans used a passive bistatic system during World War II. This system, called the Klein Heidelberg Parasit or Heidelberg-Gerät, was deployed at seven sites (Limmen, Oostvoorne, Ostend, Boulogne, Abbeville, Cap d'Antifer and Cherbourg) and operated as bistatic receivers, using the British Chain Home radars as non-cooperative illuminators, to detect aircraft over the southern part of the North Sea. Bistatic radar systems gave way to monostatic systems with the development of the duplexer in 1936. The monostatic systems were much easier to implement since they eliminated the geometric complexities introduced by the separate transmitter and receiver sites. In addition, aircraft and shipborne applications became possible as smaller components were developed. In the early 1950s, bistatic systems were considered again when some interesting properties of the scattered radar energy were discovered, indeed the term "bistatic" was first used by Siegel in 1955 in his report describing these properties. One of the largest and most complex passive radar systems was the UK's RX12874, or "Winkle". Winkle was deployed in the 1960s in response to the introduction of the carcinotron, a radar jammer that was so powerful it appeared to render long-distance radars useless. Winkle was able to home in on carcinotron broadcasts with the same accuracy as conventional radar, allowing the jammer aircraft to be tracked and attacked at hundreds of miles range. Additionally, by indicating the location of the jammer, other radars in the Linesman/Mediator network could reduce the sensitivity of their receivers when pointed in that direction, thereby reducing the amount of jamming received when pointed near the jammer's location. The rise of cheap computing power and digital receiver technology in the 1980s led to a resurgence of interest in passive radar technology. For the first time, these allowed designers to apply digital signal processing techniques to exploit a variety of broadcast signals and to use cross-correlation techniques to achieve sufficient signal processing gain to detect targets and estimate their bistatic range and Doppler shift. Classified programmes existed in several nations, but the first announcement of a commercial system was by Lockheed-Martin Mission Systems in 1998, with