I have the Electra Pro Lvl 1 system installed in my home (office) with 6 extensions/phones, one of which was recently added. Actually, it was split off of a 25 wire cable by a NEC technician.
Unfortunately the new phone does not ring at all. Calls can be placed and received, but no ringing.
I have a combination of ETW-8-1 and ETW-8-2 phones, none with display...

How do I program the system for this new phone to ring, without knowing which extension was added? The NEC tech told me I have to get a display phone before he can do anything.

I am not a phone person, so please explain taking that into consideration.