[ARC5] Re volume control

[Mike Hanz]

Brian A Clarke wrote:

>In all the ARC-5s and SCR-274-N manuals, installation designs and actual
>installations I have seen, there is not one volume control. Very few of the
>Interphone amplifiers had volume controls, either.
>Therefore, the operator must use the RF gain control to control headphone
>listening level.
>

I guess I have a slightly different viewpoint, Brian - or at least 
humbly offer a clarification based on a systems viewpoint.  Every last 
one of the US inventory interphone *systems* I'm aware of has a volume 
control capability.  It may or may not be an internal pot in the 
interphone amplifier - as you correctly pointed out, but every last one 
of the station boxes has a volume control.  See 
http://aafradio.org/flightdeck/Interphone_systems.html for a rundown, 
including schematics.  In addition, the J-22 jack boxes in the ARC-5 set 
have volume controls, for those installations which get their audio feed 
directly from the ARC-5 receivers.  The constant nagging of the command 
set instructions WRT the RF gain control is to "set for maximum 
tolerable noise" (a setting I sometimes employ in discussions with my 
bride :-P )  but that is an action quite separate from the volume setting.

>The AVC was necessarily crude in these sets ....
>

In the ARA and SCR-274N systems that is an accurate assessment, but the 
ARC-5 sets had a pretty standard AVC system as a part of the "continuous 
product improvement" evolution of the ARC sets.  It's one of the reasons 
I chose the ARC-5 for my "flight deck" as opposed to the two earlier 
sets.  I think it's important to remember that these so called "command" 
sets were also pressed into service as liaison sets on some aircraft, so 
it's tough to characterize them into a single functional area.

73,
Mike