Touch Tone wiring

App_rpt-users
1

have a 35AF3?? touch tone pad in a mounting, I know it works when put across a telephone line, like it should.

and I KNOW I saw someplace how to wire one to work with a 9 volt battery.

I have been messing with this thing ( no constantly) for a couple days and can’t get to work with 9 volts,

when I know it actually works at a much lower voltage in “telephone” service.

I also know that I have seen, at one time, at least one article , but I am unable to find anything now.

If anyone knows of this article, or a similar one, could point me to it.

Thanks

Don K8ZGW

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If this is what I think it is, You are talking about a dtmf modulator.
I dont know the exact model you are talking about. But I do know that years ago, when I was building box for friends that would send tone on a line with out have a load on it… ( dont ask why please) I was building them with a 9volt battry with a resistor in serie then I was coupling the cable to use to the “line” with capacitors.

The resistor was just high enough in resistance for the circuit to work. it took me some time to figure it out. As I was doing like you, putting the circuit on a tel. line and it would work perfectly. But directly withe tha battery it would do nothing. The trick is that the resistor limit the amount of currant and that is how it creat the signal as it saturate then unsaturate the current coming from the resistor making the voltage vary in turn and that is where the sound come from
.

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I found my problem, my current limiting resistor was to big.
I changed it from 1 K to 330 ohms, and it works like it should now!

Don