Low Voltage-Emergency Phone Question

[eyerh66]

We are having a technician replace our emergency phones and we have several that are not receiving dial tone. He is using the same model of Talk-A-Phone that we have always used without issue.

Talk-A-Phone is telling our tech that the phones are not receiving enough voltage. Interestingly, if I swap the ports for a phone that does work with one that doesn't, it doesn't make a difference in that the working phone still works and the non-working phone still does not.

The technician asked if there was anyway to boost the voltage coming out of the analog cards in the PBX. I have never had this as an issue so I'm hoping someone can shed some light on what, if anything, can be done in the PBX.

As an adendum, I am using TN793B analog cards in my PBX.

Thanks!