AT&T MERLIN LEGEND System Reference Manual page 145

Features
Feature Interactions
Account Code Entry
Auto Answer All
Auto Answer Intercom
Automatic Line Selection
Barge-In
Callback
2-96 Coverage
If a sender calls a receiver, the call follows any individual or Group Coverage
pattern programmed for the receiver. However, if a receiver calls an
unavailable sender, the call is sent to an individual or Group Coverage
receiver programmed for the sender. If the sender is available, the call is not
sent to individual or Group Coverage receivers.
Inside voice-announced calls made by using either an Intercom Voice or
System Access Voice button that are subsequently sent to coverage are not
voice announced but ring at the receiver's telephone instead.
When answering calls on a Primary Cover, Secondary Cover, or Group Cover
button, a receiver cannot enter an account code. The account code must be
entered from the sender's telephone. (If the receiver tries to enter an account
code, no error tone sounds and the account code does not appear on the
SMDR printout.)
Since Cover buttons are not required when the QCC queue is programmed as a
receiver for a Coverage group, a QCC system operator can enter account
codes and the account code appears on the SMDR printout.
Auto Answer All is used when a receiver with an analog multiline telephone
wants Individual or Group Coverage calls answered by an answering machine
connected to the telephone.
Auto Answer Intercom does not allow a receiver with an analog multiline
telephone to use a Hands-Free Unit to answer calls received on a Primary
Cover, Secondary Cover, or Group Cover button.
Primary Cover, Secondary Cover, and Group Cover buttons cannot be
programmed in an Automatic Line Selection sequence since the buttons cannot
be used to make calls.
Barge-In can be used for Individual or Group Coverage calls answered at any
receiver telephone.
The sender and all coverage receivers must be busy before a call to a sender
can be queued. The call is sent to coverage before it is put in the Callback
queue. Once a call is in the Callback queue, it is not sent to coverage again.
The Callback call indicating that a busy extension or pool is available is not
eligible for Individual or Group Coverage.