operating a Motorola DTMF mic.

hsfdchief200 · Post by **hsfdchief200** » Thu Feb 03, 2005 7:11 pm

I have just acquired a Maxar 80 with a DTMF mic. to use as a base station in the fire station. I have never answered the telephone or paged with a mobile radio, so this is new. To answer the telephone or page a station, do you have to press and hold the PTT button, then push a DTMF button? Or do you just press a DTMF button without having to press PTT?

I don't have the power supply yet to test it; otherwise, I would find out myself. Can someone tell me which way the DTMF mic. works?

Post by **akardam** » Thu Feb 03, 2005 7:25 pm

As far as I know, on all of the mobile DTMF mics, all you have to do is to press the key itself. My Spectra DTMF mic makes a short little high pressed squeal every time you hit one of the DTMF keys. However, it apparently won't do anything when the PTT is pressed.

1motoman · Post by **1motoman** » Thu Feb 03, 2005 9:08 pm

Yes & no.

There are jumpers in the mic that can change the operation of the buttons.

Look in the manual to configure it to your needs.

kcbooboo · Post by **kcbooboo** » Fri Feb 04, 2005 4:40 am

I have a DTMF mike manual. Basically when you push the PTT button, the DTMF circuitry is disconnected and the mike element is connected. The only audio path for the DTMF tones is through the unpressed PTT button. When a DTMF button is pressed, the piezo-electric speaker is heard, but the mike is out of the circuit and does not pick it up. Pressing any DTMF button will also key the radio, but you probably will have to hold that first digit a bit longer than the rest so the receiving end gets it properly.

The various jumpers can be used to set how long the tone comes out (continuously or for a hundred milliseconds, for example), and a few other functions.

There's a schematic elsewhere on BatLabs with footnotes that explain the jumpers, but it's not easy to read.

Bob M.

hsfdchief200 · Post by **hsfdchief200** » Fri Feb 04, 2005 6:39 am

Thanks for the help. I wasn't sure about how the Motorolas operated. On all of the Kenwood portable radios with keypads that we have, PTT has to be pressed before it will send a DTMF tone.

Thanks again.

kcbooboo · Post by **kcbooboo** » Sat Feb 05, 2005 6:12 am

Back in the 70s when amateur repeater autopatches were popular, I always had to press my PTT button more as a safety feature incase I put the HT down on something.

I can see that there are good points and bad points for having to only press a digit instead of both the PTT and a digit, but maybe I'm just a creature of habit. I know my first experience with a Motorola DTMF mike was that it didn't work; then I RTFM and saw the light.

Bob M.