the Network port ...that is a dual purpose , it can be used for programming and where the IP phones " connect to " sort of.
if nothing was wired to lines 1,2,3,4, it probably has a PRI card in it.
You really need to Connect to it to see what is really there. The IP phones require Licenses in the system


I can see the light at the end of the tunnel..

Retirement 2019 ( It has happened )