AT&T MERLIN LEGEND System Reference Manual page 293

Features
Single-Line Telephone
Considerations
2-244 Night Service
QCC system operators can only use the programmed button. However, DLC
system operators can also activate Night service by pressing the Feature button
and dialing 39. When a feature code is used to activate or deactivate Night
Service and Outward Restriction is programmed, the DLC system operator does
not hear an error tone if an invalid password is entered and, unless a Night
Service button is programmed, cannot determine whether Night Service is active.
To make a call when Night Service with Outward Restriction is assigned, the
multiline telephone user presses the Hold button and dials the password before
lifting the handset. When the correct password is entered, the user can lift the
handset and make an outside call.
Single-line telephones cannot make outside calls when Night Service with
Outward Restriction is activated.
A direct inward dialing (DID) call to any member of a Night Service group
rings at all group members' telephones.
If the telephone assigned to a Night Service group has the outside line
assigned as a personal line (assigned to a button on the telephone), calls
ring immediately at each telephone even if the Personal Line button on the
telephone is set for Delayed Ring or No Ring. If the telephone does not have
the outside line assigned, the call rings on an Intercom or System Access
button.
When Night Service is deactivated by the system operator or automatically
by the system, telephones are reset to their programmed ringing options.
When a feature code is used to activate or deactivate Night Service and
Outward Restriction is programmed, the DLC system operator does not hear
an error tone if an invalid password is entered and, unless a Night Service
button is programmed, cannot determine whether Night Service is active.
When both Night Service with Outward Restriction and Night Service with
Time Set are programmed, the system imposes restrictions automatically.
When Night Service with Outward Restriction and/or Night Service with Time
Set is programmed, Night Service is activated or deactivated for all system
operator consoles. If Night Service groups are also programmed, Night
Service cannot be activated or deactivated for each group independently.
When Night Service with Outward Restriction is activated, and a user with a
restricted telephone presses a dial pad button while on a call, the call is
disconnected, the user hears a fast busy signal, and the line/trunk is
released. When the dialpad is used, the system assumes that the user is
trying to make an outside call, which is not allowed because of the Night
Service restriction assigned to the telephone.
System operators can override Night Service with Time Set and turn Night
Service on or off manually. However, Night Service is activated or
deactivated for all consoles and for all Night Service Groups.
Night Service with Time Set can be deactivated through system
programming for special conditions such as a midweek holiday.