MFJ-1272B
Instruction Manual
2
Installation
Before you install the MFJ-1272B TNC/MIC switch, you must set it up for your
particular radio. The MFJ-1272B comes pre-wired from the factory for Kenwood
and Alinco radios
without
RECEIVE AUDIO on the microphone jack. If you have
one of these radios, the TNC/MIC switch is ready to use. If you have a Kenwood or
Alinco radio
with
RECEIVE AUDIO on the microphone jack, or if your radio is not a
Kenwood or Alinco refer to the configuration section. We have given a few
diagrams for placing the internal jumpers for a few popular radios on Page 6.
Configuration
If you must configure the TNC/MIC switch for your radio, please follow this
procedure.
1.
Remove the two screws and top cover of the MFJ-1272B.
2.
Look at the writing on the unit's pc board. Please refer to Tables 1 thru 6 as
to where to place the jumpers in relation to the pinouts on your radio.
Consult
your radio's manual
and the definitions below to match signals.
Audio Out:
Audio to the from either the TNC or radio MICROPHONE.
PTT:
This is the Push to talk signal from either the TNC or radio microphone.
Receive:
Audio from the radio to the TNC. Please refer to the
External Audio
section
on the following page, if you use external audio make no connection here.
Audio In:
Audio from mic (same # as
Audio Out
)
Ground:
This is the system ground on radio's mic connector. Some radios have two
ground pins, MICROPHONE GROUND and GROUND. The microphone
ground
should not
be used, due to the possibility of introducing "hum" into the
system
.
Always use the pin labeled ground.
Throughs:
Connect all pins here except MICROPHONE AUDIO.