AT&T MERLIN Plus Training Manual page 74

To use auto answer-all:
Action
Touch the Auto Answer-All
button.
To cancel auto answer-all:
Touch the Auto Answer-All
button.
Note: You can program both an Auto Answer-Intercom button and an Auto
Answer-All button, but you can use only one at a time.
68
Result
If the button has lights, the green
light will come on.
The external unit is turned on.
Whenever a call is received, it will
be picked up by the external unit.
The green light goes off.