[Milsurplus] Ideas on Japanese circuit ?

[Hubert Miller]

The detector tube is a triode with no plate B+. The plate has a negative bias on it so it's DAVC.
The triode 1/2 the 6F7 HFO only gets its plate voltage when 1) the BFO switch is ON and 2) the 
switch shorts out the BFO tuned circuit. My thinking now, subject to revision at any moment,
is that this is for A1 CW sidetone. A2 A3 sidetone are delivered from transmitter via cable to the
receiver headphone circuit. But this won't do for A1, no audio. This is my guess for now. "Our 
mission, if we choose to accept it". It seems no one in Japan has any WW2 Japanese aircraft
radio working. The websites i have looked at there, a lot of interesting info on history but it
seems they're not up to component level analysis. 
Thanks for all inputs. I have asked Takashi Doi for the voltages marked on dynamotor nameplate.
Lacking that, i would go for "reasonable" guesstimates.
-Hue Miller