AT&T MERLIN LEGEND System Reference Manual page 296

Features
System Access
System Programming
Related Features
In the Hybrid/PBX mode, Night Service calls override any ring options (Delayed
Ring or No Ring) programmed for System Access buttons and ring immediately.
On Shared System Access buttons, Night Service calls follow the programmed
option (Immediate Ring, Delayed Ring, or No Ring).
Assign or remove telephones from the Night Service group.
NightSrvce -> GroupAssign
Select the Night Service with Outward Restriction by assigning a password.
NightSrvce -> OutRestrict
Add or remove telephone numbers from the Night Service Emergency
Allowed List.
NightSrvce -> Emergency
Assign or remove telephones trom the Exclusion List.
NightSrvce -> ExcludeList
Select the start time and stop time for each day of the week for Night Service
with Time Set.
NightSrvce -> Stop -> Day of Week
Call Coverage
Call Restrictions
Night Service 2-247