THANK YOU to both of you for the info, that's very helpful.

Yes, it's a BLUE box so it's digital. The client said they had the unit installed about 15 years ago. The only labeling on the outside of the box is "Vodavi", the label is hidden on the back of the unit and can only be seen when the unit's removed from it's wall bracket.

If I get it working, I'll report back, won't get to check it out until Saturday.