This article describes how to make a simple adaptor that can be used to a push-to-talk (PTT) switch to a Motorola earpiece with boom microphone. No modifications are needed to the original headset or to the Talkabout radio. The headset is shown in the picture below and is available on-line for about $15.00.
The Motorola headset. Part #56320
Getting a 2.5mm stereo plug that fits the radio is a problem as the Motorola plugs are about 2mm longer than standard. For an earlier adaptor I used a Radio Shack 2.5mm right-angled plug and machined down the shaft to make it longer. The procedure described here makes use of a plug salvaged from another Motorola earpiece.
The Motorola earpiece sacrificed for its plug.
The Motorola plugs are wired as follows:
| Sleeve | Common |
| Ring | Microphone |
| Tip | Speaker |
To determine which wires did what in the earpiece, I opened up the microphone/PPT block.
Inside the Motorola microphone assembly.
There are two wires from the plug: one for the speaker and one for he microphone. The speaker wire contains two conductors: one red and the other gold. The microphone wire contains a white conductor covered in a copper screen.
The stripped earpiece wires.
The wire for the speaker connection is made of plastic-covered strands. You can solder the ends by heating them enough before applying the solder. There is no need to try and strip each of the tiny wires. The white microphone wire has plastic strands in with the copper wires. These melt away when you tin the wire.
The idea for the adaptor is to use the plug and wire form the small earpiece and connect that to one 2.5mm stereo socket into which we'll plug our headset and a 3.5mm mono socket into which we'll plug our PTT switch. I decided to use an additional socket for the switch so I could change switches easily.
I used the following Radio Shack parts to make my adaptor:
2.5mm (3/32) stereo socket. Part # 274-245 (package of 2)
3.5mm (1/8) mono plug. Part # 274-286 (package of 2)
3.5mm (1/8) mono socket. Part # 274-333
SPST switch. Part # 275-609
I also used some two-conductor screened wire, part # 278-513.
The switch assembly is made by wiring the switch to one end of about three feet of the screened wire and the 3.5mm mono plug to the other end. You can cut the screen off at the switch end. At the plug, connect one of the conductors and the screen to the body of the plug and the other conductor to the center tip of the plug.
I used a lot of heat-shrink tubing to insulate the wires to the switch and to make the unit more stable. You could also fit the switch into a plastic tube etc.
The screened wire showing the two conductors and the screen.
The wired 3.5mm plug.
The wired PTT switch with heat-shrink over the solder joints.
The finished switch assembly.
The next part involves wiring the 25.mm socket, the 3.5mm socket and the salvaged 3.5mm plug.
Before soldering the wires to the socket, strip and tin all the ends and join together the microphone screen and the gold speaker wires. (These are joined together in the plug).
The Prepared wires.
In the picture above, all the wires are inside a piece of heat-shrink tube.
The wired 2.5mm stereo socket.
The final assembly was covered in more heat-shrink tube.