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# Special wiring notes on the 514A-7 control head
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This control head supports programmed channels which make life much easier
for the system user. It will allow the user to have 10 programmed channels
that are stored in memory. In theory, the head provides scanning capability 
of the programmed channels.

To use the 514A-7 head, you need to wire it with its own power and 
it also allows for special audio handling if needed.

The 514A-7 does not use "Control Power" from the RT (Pins C and D).  
Positive (+) 28 VDC is supplied to the A-7 on Pin W (return is lower case r).  

If the cable harness is wired for the 514A-7 power, it will not affect operation 
if you need to use the 514A-4 head as a replacement head as the Pin W is not 
used in the 514A-4 wiring configuration.

The A-7 also has a volume control (the A-4 does not).  
So you can route receive audio through the control head if you are using a 
headset or a fixed setting on the audio amplifier for a speaker.  
This is not normally used when the 600 Ohm audio lines are connected to a data modem.

The 600 ohm audio in on lower case "a" and return "M".  
Volume control output from the control on lower case "c" (Hi) and lower case "j" for audio low.

A detailed wiring diagram is coming.