702A

Three electrode twin TR switch. The first TR switch was made in England around the mid 1941 at the Clarendon Laboratory. As switch it used the resonating horns of a Sutton early klystron, the NR89, filled with low-pressure water vapour. A similar approach was followed at the Bell Telephone Labs., inserting gas in the electrodes of an experimental klystron device, the 712A, similar to 402A and forerunner of the 707A. The cathode and the repeller were then suppressed and replaced by glass caps.

702A was similar to 709A, but usable for longer wavelengths.