This modification is for commercial radios, I am using it successfully with my Motorola GM340, but there is no reason why it should not work with other models and makes.
My own Motorola GM340 node.
The starting point is my previously described design using surface mount resistors. But as you go along with the modification you should plan and fit in the three extra components I have described below.
However, for a commercial radio such as my GM340 there are three additional modifications which should be made.
- Cut out the additional track as shown, and solder in a BAT43 diode.
- Add the blue wire which is a ground wire.
- Add a 20K resistor to the yellow Rx point { mic }.
All completed as far as the sound fob modifications go, with a bit of a squeeze it is possible to fit all the components on to the CM108 board.
All that remains is to connect the modified sound fob to the GM340 data connector. { Note the black wire occupying the socket below the bare ground wire, this is hard to see in the photo. }
I actually salvaged this cable, but the connections I used to the CM108 sound fob are as follows.
- Red to red on the sound fob.
- The bare earth wire to the blue wire on the sound fob.
- The black wire to the white wire on the sound fob.
- The white wire to the black wire on the sound fob.
- The green wire to the yellow wire on the sound fob.
This should give you all the information you need to put together your own cables.