Some of the Army radars pre-date the introduction of this classification system and had their own nomenclature that tended to remain in use even after they officially received new names.
1 was assigned after the systems were already being replaced, and they were never widely referred to by the new name, remaining better known as GL Mk.
These radars were associated with individual searchlights, providing their operators with enough directional information that the target aircraft could be picked up in the beam of the light.
This frequency was originally developed for airborne radar systems, using shorter wavelengths than Chain Home in order to reduce the required antenna size.
Over 10,000 of these early SLC radars were built in a production run spanning from June 1940 to December 1943.
8 and 9, which used a cavity magnetron to work in the 10 cm microwave band, allowing the antennas to be greatly reduced in size.
These were given very low priority due to the arrival of larger microwave radars that could directly guide guns without searchlight assistance, and ongoing improvements to ground controlled interception and aircraft interception (AI) radars that meant that searchlights were no longer needed to assist night fighters.
These units had long development periods and only began widespread deployment in 1943, when they were quickly overtaken by the US SCR-584, and production was curtailed.
It saw widespread service during the late stages of the war, and was especially valuable during the V-1 flying bomb campaign of 1944.
5's, along with their M10 predictors and the VT proximity fuse, were able to easily hit the V-1 and shot them down in large numbers.
Further development of the Glaxo concept along with improved electronics led to the "Blue Cedar" experiments, which entered service after the war as AA No.
Blue Cedar also served as the guidance radar for the UK's first surface-to-air missile, the Brakemine.
To address this problem, the Canadian National Research Council (NRC) took some of the ASV Mk.
The ZPI also interfered with signals from other 1.5 m units, which were used in a wide variety of roles, so the ZPIs were used primarily on the continent.
Developments in the UK led to similar medium-range systems using the magnetron in place of the 1.5 m equipment.
Modifications of this unit to provide a plan-position indicator display allowed it to be used for medium-range tactical control, producing the Mk.
Similar adaptations made by the NRC in Canada led to the Microwave Zone Position Indicator, or MZPI, which also found use in the UK as the No.
5 PPI radars were used at the Anti-Aircraft Operations Rooms (AAOR) to allow them to see aircraft movements over a large area and assign gun units to particular targets.
Short-range AA is a very difficult task to automate because the aircraft appear only for moments, have high crossing speeds, and are often close to the ground so clutter is a significant issue.
Number 6 was designed to make a rapid line-of-sight range measurement while pointing the gun was handled manually as before.
AA Number 7 was part of a combined Fire Control System (FCS) for the Bofors guns.
The operator of the scanner would select targets, causing the gun laying cabin to slew onto the right bearing.