From the book:
7 December 1941The key to the Hawaiian Islands air defense was the air warning system (AWS), consisting of radar units, an air warning center, and the 14th Pursuit Wing at Wheeler. As the heart of the AWS, the air warning center contained an information center, fighter director, and an aircraft/antiaircraft weapon control system. The information center needed to receive data about incoming aircraft, either from long-range reconnaissance, units stationed on the outer islands, surface ship contact, or radar in order to operate. Aircraft plotters marked the flight paths on a table map where the director, with liaison officers from the bomber and fighter commands, the Navy, and civilian aviation identified them as either friendly or unknown. If marked unknown, the director ordered fighter interceptors launched, under the aircraft controller's direction, to investigate. This was how the British operated their aircraft warning system, and in theory this was what the Hawaiian Department had in place at Fort Schafter. In actuality the system used in Hawaii bore little resemblance to the British system.
The Air Force Story
The whole AWS idea was so new to the Army that no one was sure how to make it work or who should control it. The cooperation needed among various military units and government agencies was far greater than anything anybody realized at the time. Because the mobile radar systems were the first units developed for the AWS, the Army Signal Corps took initial control. After the Signal Corps had set up the system and trained the personnel, control would pass to the Air Force. Contrary to popular belief, the Air Warning System as used in Hawaii on 7 December 1941 was under the Army Signal Corps, not the Hawaiian Air Force.
The radar systems in use on 7 December were SCR-270-B radio sets. They were mobile units housed in two trucks. The unit's heart was the oscilloscope that gave a picture similar to a heart monitor in hospitals today. The operator would move the antenna through a given arc until the line across the bottom showed a small spike or "pip." By adjusting the antenna and the controls on the set, the pip was enhanced until the operator could tell the approximate distance to the target. Next, the operator would look out the window to a plate mounted on the antenna base, with an arrow on it that would give the direction of the contact. Unlike today's radar scopes the antenna did not oscillate and there was no constant repainting of the picture on the scope. This system could not tell an incoming target's altitude, its size or number, nor could it differentiate friend from foe.