Can anyone guide me on this issue: I am the site admin for an office, and when I came into work this morning about half the phones have no display, no dial tone.. nothing. All other phones are completely functional. There does seem to be consistency in the location of the phones. In the mid section of the office is where the majority of phones died, also a group in the back of the office as well.
What are some of the reasons for this?
What info can I provide to help troubleshoot?

Thanks for any insight, i do not have much experience with this phone system.

It could be a bad circuit card or perhaps a feed cable was cut or damaged.

Any chance it's a total of 16 dead phones? That would strongly suggest a bad card or cable.