[MRCA] Info Needed on Signal Corps RM-12G Remote Control Unit

[Christopher Bowne]

Lately I have been using an RM-12G to couple line level audio from an external 
audio chain into my various old radios that otherwise are designed to work with 
carbon microphones.  Feeding in the audio via one of the two line inputs works 
very well, and the LOCAL/REMOTE switch can be used  as T/R switch which 
otherwise has to be done with a switch plugged into a key jack, or via a 
separate set of leads brought out from the microphone connector.  Its amazing 
how good the modulation pattern of a screen modulated command set can look when 
fed clean audio this way, and I've gotten favorable audio quality reports.  
"Test audio" from this setup into a dummy load sounds quite nice on local 
monitor receivers.

I am now curious how this unit was used in practice - it appears that it was 
used along with another unit the RM-13, with radios such as the SCR-299/399.  I 
have not been able to find any useful documentation on these units.  From what I 
can tell so far by working with the RM-12, it can couple remote audio (from an 
EE-8 field phone maybe, or perhaps another RM-12?) into a transmitter, and key 
the transmitter from its front panel, and it will accept a carbon mic and a key 
into its front panel jacks that can operate with the transmitter.  However, how 
remote T/R operation from a position located away from the RM-12 unit located at 
the transmitter is not clear to me.  Also, there does not seem to be any 
provision for sending audio from a receiver to a remote location.  Was that done 
through the RM-13?  It also appears that it can be used as a field phone with a 
built in magneto and handset - to talk to an operator at the other end of the 
remote circuit?  I have not been able to key/modulate a transmitter with the 
handset so far. 


Would be fun to have one of these systems set up and operating a remote station 
via twisted pair at NEARFEST or Gilbert sometime.