DTMF MIC MOD FOR IC-910 & IC-746
I've owned the 746 and 910 for years and have never understood why I spent $1,800.00 for a nice rig but needed to use my HT to program my repeater controllers or access my own IRLP. I found an answer and it works great. I bought the Icom HM-118TN. It's a commercial grade Motorola feeling Icom hand mic, has a backlit key pad and Up /Down control buttons. The obvious issue of course is that it has the modular termination. Before you start, it will be helpful to download the manuals for the IC-2200H and and print the mic wire diagram on page 2. Print the mic pin diagram for the IC-910 on page 15. Now you can make notes on both as the pin designations use the same terminology.
After carefully stripping back the rubber casing and removing the many string strain supports, you will find the pin#)colors as follows: 1)Red: +8V DC, 2)Brown: Channel Up/Dwn, 3)Yellow: 8V Control, 4)Green: PTT, 5)Copper: Mic GND, 6)White: Mic Audio, 7)Grey: GND, 8)Blue: Data IN. After the mod, you will not be using yellow or blue wires, but the touch tone pad will operate, it will be back lit, and the UP / Down buttons will work also.
On your 8 pin mic connector, attach the following: 1)White: Mic, 2)Red: +8V DC, 3)Brown: Up/Down, 4)-unused-, 5)Green: PTT, 6)Grey: PTT GND, 7)Copper: Mic GND, 8)-unused-.
I have tested the mic on the IC-910 and IC-746 at low and high levels and the touch tones were accepted my my controller at all levels. The gain of the mic sounds better with the level high on the radio.
Edward F Thomas, W2EFT