Does anyone have a “B” model?

It looks like a regular compact 28KSR (AN/UGC-20 or 20A), except……

It has a photoelectric keyboard and distributor like the TEMPEST AN/UGC-77 but also includes an internal keyer card so it will key a 60ma loop (or output a 1.5v/70uA signal). 

So no +/-6v low level signaling capability. 

I just received the manual and will scan and post it in a few days. 

Verrrry Interesting…….