Re: Phone line interface for DTMF

On Fri, 22 Jun 2007 19:04:46 GMT, "jmarc"
<jmarc@xxxxxxxxxxxxxxxxxxxxx> wrote:

Hi all,

I would use a 600 ohms phone line transformer
to have dc isolation, for transmitting DTMF from
a computer.

My very simple desing work at home, but
doesnt work at the office. It seams I don't
deliver enough audio level of DTMF.

Earlier, I bought a very simple "play/record"
device who did work (more audio DTMF level),
but humming soon happen with differents
configuration.... (not use transformer in)
It is probalby caused by different ground
voltage level, between computer and Telco gnd.

Is someone out there, can rely me to some pretty
schematics on the web, or have any suggest
to do it right?

jmarc...


Tomi Engdahl has a fairly comprehensive tutorial on telephone line
interfacing here for you to study.
http://www.tkk.fi/Misc/Electronics/circuits/teleinterface.html
.

Relevant Pages

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  • Re: Phone line interface for DTMF
    ... I would use a 600 ohms phone line transformer ... deliver enough audio level of DTMF. ...
    (sci.electronics.design)