Iwatsu ENTERPROSE-CS Owner's Manual page 206

Menu Operations in Group Ringing Mode (Forced Night)
When an ECS system is in the Group Ringing Mode, pressing the existing
Night Mode key from an Iwatsu ICON Series attendant position (5810, 5910
and 5930) will take you to the Select Ringing Mode screen with limited
selections. The menu will prompt the attendant to select either In Forced Night
(System Night Mode) or In Group Mode. If In Forced Night mode is selected,
all trunks are forced into the system night mode. When In Group Mode is
selected, the trunks return to the mode selected by the Trunk Group key.
This operation has a System Night override for each ringing group. For
example: All trunks will generate ringing based on the Night ringing table.
Key Lamp Indication for Day-1, Day-2, Day-3, and Night Mode
The Group Night Mode key will change the LED lamp status based on the
Group Ringing mode. The LED lamp indication is reflected for the ringing
mode on all Iwatsu telephones (legacy and ICON Series) with a Night Mode
key.
 Day-1 Ringing Mode = No lamp indication.
 Day-2 Ringing Mode = Slow red flash.
 Day-3 Ringing Mode = Fast red flash.
 Night Ringing Mode = Solid red flash.
Note: Iwatsu ICON Series Self-Labeling Key name change is not supported
with the Multiple Ringing Mode.
ATTENDANT POSITION USER GUIDE - 188