FYI
A Viking SO-24 has ability to monitor 24 ports (one at a time) accessable through a single line phone. It's very versitile, and it comes with cords to attach a regular tape recorder (they recomend a radio shack recorder in the documentation. You can start recording at any time during the conversation. I've installed several for customers that are very happy with them. The best function of this unit is that it has a slow bleed into the conversation. That means the other parties on the line will not hear the intrusion. I haven't had any complaints yet. Hope this helps!