No Internal Dial Tone to any Multiline Terminal or SLT
Incorrect or No DC Voltage
Check AC Input Power.
DC Voltages Correct?
AC Power?
Turn system Off. Disconnect all circuit boards.
Turn system On. Dial tone on Multiline Terminal on 1st ESI(8)-U( )
(MBD-U10 Unit)?
Correct AC Power Problem.
Replace Fuse(s).
Bad PSU Fuses
F1 & F2 ?
No Dial Tone
Replace Corresponding Power Supply.
Yes Problem Solved?
Reset ESI(8)-U( ) ETU. If trouble persists, replace B48-U10 KSU.
Dial Tone?
Dial Tone
Rebuild system, one card at a time until problem reappears. Replace defective card.
Dial Tone
Remove all ETUs and retest.
Problem Solved?
Build system one card at a time, and replace bad ETU(s).
No Replace KSU.
No Dial Tone
1. If problem not solved, perform First Initialization and test. If trouble persists, go to step 2.
2. Replace B48-U10 KSU and test system using default program.
For AVAYA, NORSTAR, NEC, SAMSUNG, MITEL, PANASONIC, TOSHIBA telephone systems and voicemail call (866)206-2316 or email