NEC SL1100 Features And Specifications Manual page 371

ISSUE 2.0
3. Dial 00 ~ 13 to enter the Threshold.
After you dial the Threshold you will hear a "Beep" sound.
4. Press Speaker key after you dial the Threshold.
To Cancel Automatic Backlight:
1. At Multiline Terminal press Speaker key and dial Service Code (706).
2. Dial 0 to cancel the Automatic Backlight.
After you dial 0 you will hear a "Beep" sound.
3. Press Speaker key after you dial 0.
Features and Specifications Manual
SL1100
I
1-359