Re: Telephone interface

Article View: sci.electronics

Article #11881

#11881

From: Mike Fox
Date: Tue, 06 Oct 1992 23:24

31 lines
1797 bytes

In article 1agi51INNc58@usenet.INS.CWRU.Edu, at847@cleveland.Freenet.Edu (Jeff Hunsinger) writes:
> 
> This has got to be an FAQ, but I just read about 100 subject lines
> and didn't find it. I am trying to hook up a DTMF decoder (SSI202)
> and a voice synthesizer (amplified with an LM386) to a telephone line.
> The DTMF decoder works fine so long as I don't hook up the amp.
> I tried putting an amp before the decoder, but that doesn't seem
> to work either.
> Here's my current set-up:
> 
> ----Cap--- 600:600 ohm matching transformer-> amp -> ssi-202
>                                            <- Amp -< voice synth.
> 
> Any help?
> Jeff



You need to use an op-amp as a duplexor so the speech
does not interfere with the DTMF signalling. Something
similar to:
               
                speech >--|\
         ---              | -----to DTMF recognizer
Tip-----|   |-------------|/
        |   |
Ring----|   |-Ground
         ---
        600ohm 1:1 IsoXformer

/Mike

Technical Details

Message-ID: <1992Oct6.232422.7032@exu.ericsson.se>

Path:

arc1-ca.pugleaf.net!sparky!uunet!haven.umd.edu!darwin.sura.net!zaphod.mps.ohio-state.edu!cs.utexas.edu!sun-barr!west.West.Sun.COM!cronkite.Central.Sun.COM!texsun!exucom.exu.ericsson.se!s11a08!exumfox

References: <1agi51INNc58@usenet.INS.CWRU.Edu>

Show Full Headers

Complete Article Headers

Path: arc1-ca.pugleaf.net!sparky!uunet!haven.umd.edu!darwin.sura.net!zaphod.mps.ohio-state.edu!cs.utexas.edu!sun-barr!west.West.Sun.COM!cronkite.Central.Sun.COM!texsun!exucom.exu.ericsson.se!s11a08!exumfox
From: exumfox@exu.ericsson.se (Mike Fox)
Newsgroups: sci.electronics
Subject: Re: Telephone interface
Message-ID: <1992Oct6.232422.7032@exu.ericsson.se>
Date: 6 Oct 92 23:24:22 GMT
References: <1agi51INNc58@usenet.INS.CWRU.Edu>
Sender: news@exu.ericsson.se
Reply-To: exumfox@exu.ericsson.se
Organization: Ericsson Network Systems
Lines: 31
Nntp-Posting-Host: s11a08.exu.ericsson.se
X-Disclaimer: This article was posted by a user at Ericsson in North America.
              The opinions expressed are strictly those of the user and
              not necessarily those of Ericsson.

Reply to Parent Message