Northern Telecom 3X8 Owner's Handbook Manual page 60

You can assign a Control telephone to more than one external
line, but a line cannot be assigned to more than one Control
telephone.
Only one Service Mode applies at any one time to all external
lines controlled by a given Control telephone.
The default Control telephone for all lines is 21
Service Modes
The three Service Modes are programmed in the same way.
Service Mode Name
The Service Mode Name identifies the active Service Mode, and
is shown on the display of the Control telephone when the
Service Mode is turned on.
Use the [Show] button, the
pad to program the Service Mode name. For information on
entering names, see the information in this chapter entitled
Entering names.
Programming hints
The default names of the three possible Service Modes are only
suggestions, and may be changed to any other name.
A Service Mode name can be one to seven characters.
Service Mode setting
The Service Mode setting controls how the Service Mode is
activated and deactivated. Use the
select the setting: Manual, Automatic, or Off.
PO842627 01
Service Modes 55
display button, and the dial
display button to
DR5.1 Owner's Handbook