[MLB-WIRELESS] Free P2P phones will pressure telcos

Jason Hecker jhecker at wireless.org.au
Wed Nov 12 15:49:29 EST 2003

> The way around that issue would be to interface the PC to a phone line
> simulator, which the phone plugs into.  Hmm, how easily could we simulate a
> phone line using a PC and some add on hardware?  Gee, you could have busy
> signalling and all, if the software supported it. :)  This approach would
> also allow the use of unmodified landline handsets.

Well, yes.  Phone/Linejack does this.  The most basic things you'd need 
are a ring circuit to generate about +-60AC for a load of 1 REN, a 
-60V at 20mA circuit to provide the current loop, a means of adding the AC 
and DC voltages as well as your normal audio.  Don't forget the 
transhybrid.  You can do this piecemeal  but Siemens/Infineon have a 
nice range of parts which can do all this for you.  Unfortunately you 
get a binary audio stream which you will somehow have to get into the 
PC.  All in all I think it'd be easier to muck with your cordless.

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