"M. J. Powell" wrote:

I don't remember any 'click' when the oxygen mask mic switch was used.
Some time early in the war the mic was changed from carbon to
moving-coil, using an extra amplifier in the intercom circuit.
Convention in my time was that only the pilot left his mic open all the
time, otherwise you got all the crew's breathing in your ears
continually.

Mike

Could be Mike, but you mention RAF and WW2 era. The RCAF used the
Lancaster X Maritime Reconnance version in the early to mid
fifties which indeed did still have hand held carbon mics. They
were the T-17 type and being young curious types we 'dismantled'
one and saw the carbon granules in the little pocket in there. We
were in ASW service so hardly ever wore O2 masks but I remember
that they also had those small round mics imbedded in the rubber.

Actually any intercom system (that I've used) will exhibit that
distinctive click and the hiss of background noise while the mic
is open. I recall searching for a stuck mic switch on an Argus
with maybe 20 intercom stations.

We used hot mic for takeoff and landing for the Pilots and F/E on
the Argus for instant comms. The hiss was annoying and was often
not used for that reason.

The Lanc model that we used carried a 'wire recorder' for the
sonobuoys which could likely have been wired to the intercom so
that's not a big deal but it didn't sound real to me. Mind you
now, I left Lancs nearly 50 years ago but I remember a lot about
them because I was young then and impressionable and I'm pretty
sure that that recording is fake...it's just much too quiet, no
engine noise at all...they were hellishly LOUD...the commands
just didn't sound 'right'...mind you they were RAF but still...

My considered opinion...fake...
--

-Gord.