An Icom IC-410PRO UHF transceiver is being interfaced to a Clear-Com intercom system via a TW-47.

I/O required between the IC-410PRO via it’s 8-pin RJ45 connector and the TW-47 are:

• Ground
• Mic Ground
• Mic
• AF Out

In line with the dumbing down of society , there is no mention of microphone pin outs in either the IC-410PRO Basic Manual or the “Advanced” Manual, so attention turned to a compatible microphone, the Icom SM-26 for further information.

A suitable lead was made, and it was then discovered that there is no audio output appearing on pin 3.

As the IC-410PRO Service Manual is unobtainium, a copy of the IC-400PRO was obtained.


For some odd reason, the audio output is not enabled out of the factory, so this solder link jumper needs to be found and soldered.



There is quite a bit of difference in the PCB layout between an IC-410PRO and IC-400PRO, so “CP-25” is not evident on the top-side of the PCB.

Time to pull the board out, which requires removing screws and desoldering the antenna socket and PA module beforehand.

AFO signal from the IC15 is easily seen, and this trace was followed to see where it popped up on the other side.

It turns out on an IC410PRO, jumper “G” is the AFO solder link.

You will then discover the audio level is not at a constant level, ie; post volume control.

This is a really bad implementation, Icom.

As it turns out, the AFO level was insufficient for the intended application and the 3.5mm speaker output was used instead.