a high speed aerial situated at Dundonald Hill in Ayrshire, Scotland which provided a baseline to the north of RAF Boulmer, but there was no similar extension to the south of RAF Neatishead. The signals were combined at one of the radar stations (at the location of the Type 85 forming one end of the baseline) in a phase correlator that produced a series of possible locations and plotted them as a series of blips on a unique "theta-phi" display. The operators manually adjusted gains in order to reduce the number of blips, and then sent that information to a remote display where it could be combined with normal data from the Type 85. The idea was to locate any specialty-equipped jammer aircraft within a larger attack, allowing them to be prioritized for attack, thereby lowering the ECM load on other radars. Operational training Such a complex system required that Operators be fully trained. To this end L1 had a large, digital radar simulator that was capable of generating all the radar inputs of the live system. It was ordered from Elliott Automation following the successful development of the world's first digital radar simulator by that company. Based on the Elliot 502 computer it could simulate 6 radar heads with jamming and noise while displaying over 200 aircraft. Operation Linesman, as originally conceived, never became operational. It went operational in the early 1970s but only in producing and disseminating the overall Recognised Air Picture, the General Situation Display and the Higher Formation display until 1984. The interception side was only ever used in the training role of the School of Fighter Control. The L1 got three more computers (Elliott Argus 500s) as the Recognised Air Picture Dissemination System (RAPiDS) and these disseminated the RAP out from the L1 in a more advanced format. Though the concepts remained valid, the technology used to route the radar signals was out-of-date long before the system was completed. Having the control of aircraft centralised in one place also put it at high risk. A change of plan moved the interception roles out to two of the main radar stations, where the RAP from the L1 was used to monitor the airspace while the Fighter Controllers then used the Standby Local Early Warning and Control Systems (SLEWC based on Elliott 920C computers) to control interceptions. In the original design, processed radar signals were returned from