[ARC5] Added 6F6 audio stage...Aircraft Interphones

[Mike Morrow]

Dave wrote:

> I've never understood this issue of adding audio stages to Command Set
> receivers.  I've been playing these sets stock using matched speakers
> for decades.  They have all the audio I could want, and I'm half-deaf...

The single-tube AF output stages of the MF/HF command set, VHF command set,
liaison set, radio compass, and interphone microphone amp could be fed to
approximately ten interphone stations, each capable of selecting any of
these AF sources and hearing it with headphones in a very noisy environment.
The interphone amp in all common WWII-era aircraft interphones (until the
late-war AM-26/AIC, part of AN/AIC-2) did not provide further amplification
of any receiver's AF output, even one that is connected to ten headphones.
The weak little VT-99 (6F8) of the common RC-36/BC-347-* single-tube
interphone amp was always connected simultaneously to all headsets.

So Dave's statement seems necessarily 100 percent accurate, even when a
speaker in a quiet area is substituted for those ten headphones working
against aircraft ambient noise.

73,
Mike / KK5F