NEC DSX-40 Feature Handbook page 111

For a Switched Loop key:
• Dial the Line Group code (0-8 for groups 90-98).
a.
• Dial the outside number.
For a Fixed Loop key:
b.
• Dial the outside number.
DSX Feature Handbook
Using Loop Keys
Loop Keys
In these instructions:
[Super Display Soft Key]
[Keyset Soft Key]
Features ◆ 103