Originally Posted by crotrader
I checked the output voltage on the power supply and it is producing 10VAC

You should have several voltages present:

A Battery -filtered DC for intercom talk paths- -24VDC
B Battery -unfiltered DC for relays and line card circuitry- -24VDC
Lamp Battery -AC for lamps and usually buzzers- 10VAC
Ring Gen -AC for ringers- 105-120VAC 30HZ
Buzzer -Some KSU's have this, some don't. Almost never used- 18VAC