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Throughs:
Connect all pins here except MICROPHONE AUDIO.
(unlabeled)
if you use external audio do not connect the radio pins for Receive
3.
Header HD3 controls the RECEIVE AUDIO to the EXTERNAL SPEAKER.
Place a push-on jumper on pins 2 and 3 if you want the external speaker "on"
all of the time., or on pins 1 and 2 if you want the external speaker "off" when
using the TNC.. Most people prefer not to hear audio during packet. Set this
jumper to the positions desired, according to your own preference.
4.
Replace the top and screws.
External Audio
If your radio does not have RECEIVE AUDIO on the microphone, we suggest the
use of an interconnecting cable to supply RECEIVE AUDIO to the TNC/MIC switch.
You would connect the cable from an External Speaker or Headphones jack on
your radio, to the AUDIO IN jack of the TNC/MIC switch. Therefore no jumper
connection should be made for Receive on the pc board.
Using the method above for connecting RECEIVE AUDIO to the TNC/MIC switch,
will cut off the internal speaker inside the radio. In this case, you must connect an
external speaker to the EXT. SPEAKER jack on the TNC/MIC switch. Otherwise
you will not be able to hear any signals at all from your radio.
Jumper Configuration
Because there are so many different radio configurations, we have tried to make
the MFJ-1272M as versatile as possible. With the MFJ-1272M you can virtually
connect any radio pin to just about any TNC pin, just by configuring the jumpers
properly. The following tables will show how to set the jumpers, depending on the
TNC functions versus the MIC pins of your particular radio. Be sure to follow the
tables closely, with your radio manual close at hand, to verify that you are not
shorting any microphone voltages or any other microphone signals to GROUND !
MFJ-1272M Instruction Manual
3
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