➀ Production of the high power tunable Klystron, the 4K M50.0001 A, began 64 years ago by the English Electric Valve Company. ➁ The valve operates at frequencies between 400 to 610 Mc/s and features mechanical tuning. ➂ It offers amplitude or pulse modulation and is protected through a high resistance connection. ➃ The Klystron includes focusing electromagnets, tuning cavities, and adjustable load couplers, with a typical gain of 27 db and a power output of 10kW.