AT&T MERLIN LEGEND System Reference Manual page 76

Features
System Access
Hardware Requirements
Related Features
When Auto Answer All is activated, all calls received at an Intercom or System
Access Ring, or Intercom or System Access Voice button can be answered
automatically by the device connected to the GPA. If Shared System Access
buttons are assigned, only the principal station should be programmed for
immediate Ring to prevent the call from being answered at the principal station
and at stations with the Shared System Access button.
Voice-announced calls received at the analog multiline telephone are not
answered by a device connected via a GPA since ringing current is not sent to
the device.
A GPA is needed to connect an answering device to an analog multiline
telephone.
Auto Answer Intercom
Auto Answer All 2-27