being handled at the Type 80 "Master Radar Stations". In the 1960s the Linesman/Mediator project looked to computerize the system in a fashion similar to SAGE, but was years late, significantly underpowered, and never operated properly. There was some thought given to sending directions to the English Electric Lightning interceptors in a fashion similar to SAGE, but this was never implemented. GCI is typically augmented with the presence of extremely large early warning radar arrays, which could alert GCI to inbound hostile aircraft hours before they arrive, giving enough time to prepare and launch aircraft and set them up for an intercept either using their own radars or with the assistance of regular radar stations once the bogeys approach their coverage. An example of this type of system is Australia's Jindalee over-the-horizon radar. Such radars typically operate by bouncing their signal off layers in the atmosphere. Airborne Early Warning and Control In more recent years, GCI has been supplanted, or replaced outright, with the introduction of Airborne Early Warning and Control (AEW&C, often called AWACS) aircraft. AEW&C tends to be superior in that, being airborne and being able to look down, it can see targets fairly far away at low level, as long as it can pick them out from the ground clutter. AEW&C aircraft are extremely expensive, however, and generally require aircraft to be dedicated to protecting them. A combination of both techniques is really ideal, but GCI is typically only available in the defence of one's homeland, rather than in expeditionary types of battles. The strengths of GCI are that it can cover far more airspace than AEW&C without costing as much and areas that otherwise would be blind-spots for AEW&C can be covered by cleverly placed radar stations. AEW&C also relies on aircraft which may require defence and a few aircraft are more vulnerable than many ground-based radar stations. If a single AEW&C aircraft is shot down or otherwise taken out of the picture, there will be a serious gap in air defence until another can replace it, where in the case of GCI, many radar stations would have to be taken off the air before it became a serious problem. In both cases a strike on a command center could be very serious. Either GCI or AEW&C can be used to give defending aircraft a major advantage during the actual interception by allowing them to sneak