Speaking of MCW (A2), another WW2 Westinghouse 800 cycle rig, the GP-7 generates the keying tone by merely disconnecting the filter cap in the power supply thus applying a 1600 cps pulsating voltage to the 803 PA. Keying is done through the power transformer primary as in the TBW. Doesn't sound half bad. Dennis D. W7QHO Glendale, CA