I'm going to second that you DO NOT want to send your intercom's tip and ring directly into ANY input of an amplifier. Although the intercom talk path is fed by the KSU's "A" filtered talk battery @24 volts, DC, it is still going to be upward of 10-12 volts when a station is off-hook. You'll fry the paging amplifier's input port in no time.

The 600 Ohm input on a paging amp is not designed for anything over 2-3 volts. It "sounds" like it might work on a telephone line because 600 ohms is often mentioned in telecommunications dialog, but ohms and voltages are two different vegetables.

If you can find an ITT 401-PA card, this will give you what you are really seeking.

Aside from a 401-PA card, as others have said, you can use a standard 400 series CO line card in conjunction with any industry-standard external paging adapter, such as those made by Melco, Valcom, Viking or Cooper/Wheelock. These will provide the proper talk battery feed needed to interface with a standard line card and couple it safely to an amplifier.

Ed Vaughn, MBSWWYPBX