How do you have the paging system connected to the NEC? If through the page port, you can set the NEC to do ring over external page on a per trunk basis. If you have the Valcom connected through a trunk port you will need an adapter from Valcom. As far as the power supply goes, it could be a bad PS or it could have too much of a load on it. We really need more info on all the parts you are using and how it is connected before we can help further.