AT&T MERLIN LEGEND Communications System Release 2.0 Maintenance And Troubleshooting Manual page 84

Telephone Problems
Symptom
Time appears on the display, but the incoming call information does not.
Procedure
Move the T/P switch on the side of the telephone to the center position.
Voice Transmission Troubles
Symptom
Telephone does not receive tones.
Procedure
Check the control unit and wiring with a telephone that is known to be working
properly.
Single-Line Telephone Problems
Symptom
Many single-line telephones cannot dial correctly even though they are
receiving calls.
Fixing Telephone Problems
3-6