AT&T MERLIN MAIL System Programming And Maintenance Manual page 27

Overview
Immediate Call Handling
With Immediate Call Handling, Automated Attendant Service answers all
incoming calls, both day and night. If the MERLIN MAIL—ML system is busy
and does not answer the call, additional calls (called overflow calls) will ring at
the system operator's phone, as shown in Figure 1-2.
Figure 1-2. MERLIN MAIL—ML System as Immediate Call Handler
Immediate Call Handling plays either your company's day greeting and
menus or the night greeting and menus, based on the time of the call and the
schedule set up. If you want most callers to be handled by the Automated
Attendant Service, use Immediate Call Handling.
System Services and Features 1-11