charge of projects for the RCN throughout the war. In early 1942, the frequency of the SW1C was changed to 215 MHz (1.4 m) and an electric drive was added to rotate the antenna. It was known as the SW2C and produced by the REL for corvettes and mine sweepers. A lighter version, designated SW3C, followed for small vessels such as motor torpedo boats. A plan-position indicator (PPI) display was added in 1943. Several hundred SW sets were eventually produced by the REL. For coastal defence by the Canadian Army, a 200-MHz set with a transmitter similar to the NW was developed. Designated CD, it used a large, rotating antenna atop a 70-foot wooden tower. Since the firing battalion would be some distance away, a "displace corrector" automatically compensated for this separation. The CD was put into operation in January 1942 Following the Tizard Mission meetings in Washington, it was decided that Canada would build a microwave gun-laying system for the Canadian Army. This 10-cm (3-GHz) system was designated GL IIIC, the "C" to distinguish it from similar systems being developed in America ("A") and Great Britain ("B"). (Eventually the U.S. system was the SCR-584.) A local source of magnetrons was vital, and the National Electric Company (NEC) in Montreal began manufacturing these devices. The GL IIIC was housed in two trailers, one with a rotating cabin and one fixed. The rotating one was called the Accurate Position Finder and held the primary equipment and separate antennas with parabolic reflectors for transmitting and receiving. The other trailer carried the Zone Position Indicator, a 150-MHz (2-m) radar that found the position of all aircraft within the system's coverage. In mid-1941, the REL received orders for 660 GL IIIC systems. In July, a very satisfactory demonstration of the prototype system was held, and by December, the first six systems had been built. During 1942 and into the next year, there were many technical and administrative problems. In September 1943, a decision was made to use the British and American systems in liberating Europe; thus, the large REL order was never filled. Success at the Radio Branch with the 10-cm experimental set for the Army led the RCN to request a ship-borne, early-warning microwave set. A separate Microwave Section was formed and development of a 10-cm (3-GHz) set designated RX/C was initiated in September 1941. Due to many changes in requirements from the