Hi,
I was task to move this client's analog phone lines from AT&T over to Xfinity. What I noticed is that although the line is active on the AT&T binding post, I'm not able to get a dial tone straight from my butt set. I know the line is there because when I unplug the line from the phone system I lose the phone line from an extension. Does the NEC Aspire have a very low dial tone or so on AT&T and that's why I can't hear dial tone straight on the binding post? Is it specially configured from AT&T. Plus I see some transistor plugs into the terminal block on each incoming lines,. What's that for?

You might have ground start lines from AT&T.
Connect your butt set to one of the AT&T lines, go off hook, take some wire and ground one of the leads on the butt set, see if you get dial tone.

I believe if you look in programming 14-02-14 Analog Trunk Data Setup- Loop Start/Ground Start you can verify the status.

Thank you for the tip guys, I really appreciate your response. Well we migrated the lines over to Xfinity yesterday and the calls are coming in just fine into the NEC. We unfortunately can't call out! It must have to due with the ground start. What's the reason for having ground start (for my own knowledge)? I am able to get a dial-tone from an extension but after I start dialing a local number on the phone display it shows "vacant number." ??? Any suggestions? And when I hang up on the call the line looks like is still off-hook because I get a busy tone when I call the line from outside. So the NEC is not releasing the line. Do I need to turn off "ground start" in programming? Or do I need to contact Xfinity and tell them to put a ground start on the lines?

Yes you need to turn off the ground start and change to loop start. Before loop start lines got better disconnect supervision, ground start was needed. Ground start is still superior but the standard is loop start with disconnect supervision from the telephone company.

Thank you everyone. I changed in the system to loop start and the phone line interference issue is gone! An Xfinity technician came out but said they can't or don't know how to give the line a ground start. It was expected.

Thanks for the update.