High Wycombe, RAF Bentley Priory and HMS Warrior (Northwood). As with the ROTOR plan, buildings were given "R" designations, including underground bunkers as well as above-ground technical and operations buildings. There was a serious fire in the R3 bunker at RAF Neatishead where it had to move into temporary buildings above ground for some time. In addition, the R3 at RAF Boulmer was closed down for refurbishment in December 1982 and operations moved to the Boulmer Interim Facility (BIF). Equipment The core system principle was to take the input from all sensors and enable 'The Hub Concept' where the system resources were reorganized to provide an air data processing system. This produced an RAP, (Recognised Air Picture) whereby all aircraft and air movements could identified and tracked within the UK air space. Intercepts etc. were undertaken at other sites using the information feeds from L1. It continued in operation until the late 1970s, early 1980s. The core to the system were the Type 84 & 85 primary radars. Height finding capability was provided by the Type 85 (one of the first 3D radars) and the HF200 Height Finders. As Linesman progressed additional systems were introduced to aid ECCM capability and communications. Each primary radar had an associated secondary radar (IFF), SSR 750, with the smaller secondary radar mounted on the main primary radar aerial. Primary radar T84 The Marconi AMES Type 84 was a primary "L" band radar. The main transmitting equipment was contained in a building over which the aerial was mounted; this building was given the type designation "R17". The transmitter was a magnetron in the single storey building, the signal passing through a rotating joint in the rotating cabin before being fed to the hornstacks on the aerial. The aerial was designed as two 60 foot by 21 foot elliptical parabolic antennas placed back-to-back, one acting as the radar, and the other as an IFF/secondary radar system. In practice the original IFF system was never installed, and instead more modern systems with much smaller antennas were installed on the "front" dish, either below the feed horn, or on top of the main antenna. The received signals from both the primary and secondary radars were processed at the main technical building for the Linesman site, the R12 building. Primary radar T85 The AEI (later Marconi) AMES Type 85 "Blue Yeoman" radar operated in the "S" band part of