Making a small home PBX is an iteresting project however. There may be readers here who are intersted in undertaking the engineering work to make a system like this. Heck, maybe it could become an ongoing on-line project on the 8052.com projects page. Here is some information to get someone that is interested on their way.

Here is a link to a complete project outline for the design of a small multi telephone PBX.
E&CE 355 PBX Project

There was an article in the July 1994 Circuit Cellar Magazine Issue #48 entitled The Personal PBX by Richard Newman. You can access this article by getting past Circuit Cellar articles on CD at this link: Circuit Cellar on CD. A google search on the article name and author name will yield a link to the C source code zip that went with this article.

Also there is a host of information on the web regarding circuits that are used to interface phones on the phone company end. These would be useful for making a PBX as well. Simply use google to search for "Subscriber Line Interface Circuit" or "SLIC". This will turn up many data sheets and application notes.

Another google search that will turn up information on ready made products is "SOHO PBX". That gives more than 12,600 hits alone.

Michael Karas