Abstract :
When the present work was started, t.r. cells were unreliable, having short lives and failing at unpredictable times. It is shown that the use of an electron attachment gas¿an essential feature of these switches¿could account for many of these failures. In some radar systems any unpredictable deterioration of performance is unacceptable, and a solution to this problem was sought by departing from the concept of a composite t.r. switch and evolving a system in which each duplexing function is performed by a separate switch designed specifically for that task. This approach has allowed the development of duplexing switches in which the need for an electron attachment gas is eliminated and which are therefore intrinsically reliable; by introducing a prepulse to one of these the transmitter-receiver break-through can be made vanishingly small. The average time between failures of mixer crystals in systems of this type was 6000 hours.
