Test Phone Lines on NEC SV8100
How to test the individual phone lines on an NEC SV8100 phone system
Press the Speaker button
dial #0
dial 01, 01 corresponds to the first phone line on the system
Each following line is 02, 03, 04 etc. depending on how many lines attached to the system. I frequently feel phone system documentation is hard to find online especially things to do basic testing like this.