MFJ-1272B
Instruction Manual
3
(unlabled)
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. Place the jumper 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.
4.
Replace the top and screws.
External Audio
If your radio does not have RECEIVE AUDIO on the microphone, then we suggest
the use of an inter-connecting to supply RECEIVE AUDIO to the TNC/MIC switch.
You would connect a 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-1272B as versatile as possible. With the MFJ-1272B 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 a particular radio. Be sure to follow the
tables closely with your radio manual, to verify that you are not shorting any
microphone voltages or any other microphone signals to GROUND !
