I have customer that has a NEC Elite 48 with 4 CO lines, All 4 Lines were rining then all of a suddenly it stopped ring on Line 1, line 2 & line 4 It only rings on line 3, We checked program LK4 and all 4 line buttons are set to steady green anybody run into this? We reset the switch also...
Do you haver a dial tone on those lines? Move line 3 to position 1 and test it. If no ring test a voltage on the line or ringing voltage. should be 90 - 120 Volts DC for Ring and -48V for Line.
Also, make sure someone did not accidentally put the system into "night mode".
If the system is in night mode there will be a black cube next to the time in the display of all the phones.
To set and re-set night mode dial : FTR 80 FTR
D
It sounds like his COI card got hosed!