7970 & Intercom

I’m looking for some ideas on the best way to use the Cisco 7970 as an intercom.

The only way I’ve been able to do this thus far is to register a line as a separate extension to auto-answer. The only problem with this is that if someone is on the phone, and someone else places an intercom call to that person’s line, it immediately places the current call on hold and auto-answers the intercom extension.