[Milsurplus] 50s era interphone question

[Mike Hanz]

  On 9/23/2010 6:32 PM, Mike Morrow wrote:
> Jack wrote:
>
>> What would have been the interphone system
>> used in the early 50s, on either Navy or
>> Air Force aircraft?
> Jack, Mike Hanz is the expert:
>
> http://aafradio.org/flightdeck/Interphone_systems.html
>
> I'd bet that the USAF must have made continued use of the
> AN/AIC-2 (which uses that common AM-26/AIC), and the USN the
> AN/AIC-4, among several other possibilities.
>
> There's also related information in this 1953 copy of JANAP 161
>
> http://jptronics.org/radios/Military/JANAP161/index.html
>
> which oddly (to me) does not include the AN/AIC-4.


Mike is too kind.  (I'll send you the check tomorrow...)  Actually, 
Jack's question has no simple answer. :-)

There was an interesting divergence of interphone system design toward 
the end of WWII that continued well into the 1960s.  There are some 
generalities that can be assigned to each of the two branches, though 
exceptions to the generalities abound.

One branch trended toward combat aircraft application, reflected by the 
AN/AIC-4 equipment that began to be deployed at the end of the war, and 
that had quite a long life if you include the transistorized versions of 
the AM-40/AIC but was almost totally a Navy acquisition.  It was 
basically a more modern version of the earlier Navy RL-* versions (minus 
the more complex RL-24-* series) and had a single audio bus for everyone 
on the aircraft.  That simplicity was expanded with the AN/AIC-3, which 
(as the number of channels increased) attempted to integrate all the 
separate interphone functions that formerly required a raft of different 
control/jack boxes into single control heads, creating rather large 
control heads for the primary operational roles in the aircraft (pilot, 
copilot, etc.)  These have a lot of neat switches and other controls to 
twiddle, a delight to current knob-heads who have discovered same.  The 
single audio bus pinnacle was probably the AN/AIC-8.  While the main 
designation for the postwar interphone systems became AN/AIC-*, a degree 
of confusion is more than enhanced by the Navy's preference for using 
AN/AIA-* designations, which eventually were overcome by a spirit of 
jointness (or politics, as may be the case...)  All of these appear to 
be the single audio bus type of systems.

The other branch was an outgrowth of the original RL-24 series and was 
encouraged by a concept that proliferated separate audio buses (and 
therefore separate audio amplifiers) for large aircraft crew functions.  
This was ready made for growing cold war patrol missions that included 
signals intelligence and countermeasures work, effectively isolating the 
flight crew from the primary mission crew, and essentially reduced the 
aircrew, who had no real "need to know", to bus drivers.  That trend 
began with the AN/AIC-5, and went through a bunch of variations through 
the AN/AIC-10, which from what I can see appeared to be the watermark of 
such systems and set the standard for future systems by incorporating a 
separate amplifier for the major control heads, permitting more than one 
audio bus like the AN/AIC-5, but in a smaller footprint and with more 
flexibility.  It was also the first large scale system to introduce 
aircraft loudspeakers - the LS-184/AIC-10.

So, the answer to the question is, it all depends.... :-\

73,
Mike