Soundcard/POTS interface question

Hello,

I have built one of the basic isolated POTS interface circuits, using it record a call (into the mic jack of my soundcard), or using it to play an audio file into the line (from the output of my soundcard).

Currently, I just plug into either the microphone jack or the output jack, but I would like a way to not have to keep plugging and unplugging every time I change mode from play to record.

So, would there be anything inherently wrong with connecting *both* the microphone input and the output together at the same point in the circuit? I would naturally mute the output while recording, to avoid feedback.

Will this work, or is there a more elegant solution to isolate the two points on the soundcard?

Thanks,

Jon

Reply to
Jon Danniken
Loading thread data ...

Well, if you're literally moving the jack plug from one socket to the other, without changing anything else, it might work - the levels should be similar. There's a slight risk of clipping due to over-loading, but it shouldn't cause permanent damage; however, what about when AC ringing voltage is present on the line? That could blow the soundcard. I take it your POTS interface contains an isolating transformer? What voltage do you see on the jack plug when the 'phone is ringing? Have you looked at it on a 'scope? Have you already had it plugged into *both* sockets at different times, when the 'phone has rung?

Reply to
Andrew Holme

an

jack,

circuit?

Yes, indeed. The one I have built (breadboarded) is based on this model; there are zeners on the output to limit the back end voltage:

formatting link

Don't know, and my scope is AWOL presently.

when the 'phone has

No, currently I just plug it into one or the other.

Jon

Reply to
Jon Danniken

"Jon Danniken" wrote

it

an

jack,

every

the

circuit?

two

Here's a bunch of useful information about telephone line interfacing.

formatting link

Reply to
Anthony Fremont

One "correct" way of doing this is with a hybrid transformer

formatting link

These transformers are expensive, but you can use cheaper OEP ones

formatting link

martin

Reply to
martin griffith

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.