AT&T System 25 - Manual (Page 20)

Night Service
When the attendant leaves for the night, the system can be set
so that incoming calls either ring a night bell or are directed to
preassigned telephones. See your System Administrator for the
Night Service access code.
Answering Night Service Calls
1 Lift the handset and listen for dial tone.
2 Dial the Night Service access code.
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