Newsgroups: sci.electronics.misc
Subject: Re: telephone to sound card plug
References: 
Zaphod  writes:

> Does anyone have a circuit for an interface suitable to connect an
> Australian telephone socket to a pc soundcard?

Chekc the circuit plans at 
http://www.epanorama.net/documents/telecom/teleinterface.html

Those should (at least mot of them) work pretty universally all over the 
world when connected to right wires on the telephone connector your 
country happens to use. 

> I want to try the VRS software on http://www.nch.com.au/vrs/index.html
> but don't want to spend the US $84 on their recommended device that
> according to their forum also zaps out line in sockets on some sound
> cards.
> 
> I have been lent an adapter from a friend's micro recorder and all it
> is is a couple of diodes, caps and resistors. Can't see any line
> isolation, so worst come to worst I could just copy that one and risk
> zapping an input.

Using an adapter without isolation can easily kill the soundcard 
line input and cause lots of mains frequency noise to the line. 
At worst case some part of that noise can also affect other users 
on the same telephone cable. 

And in worst case if yout housue is hit by a big power surge, 
short circuit inside computer or wring wiring on computer outlet,  
a telephone line adapter without proper isolation 
can cause dangerous voltages entering the telephone cable.
Those are potentially dangerous to telephone installation people 
(at worst case can kill somebody). At worst case can fry the  
line card on the telephone central (this will be expensice). 


-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/