AT&T MERLIN LEGEND System Reference Manual page 143

Features
Telephone Differences
Multiline Telephones
Single-Line Telephones
Mode Differences
Hybrid/PBX
Key and Behind Switch
Considerations
2-94 Coverage
Any type of multiline telephone except a QCC can be a sender and/or receiver
for either Individual Coverage or Group Coverage.
A single-line telephone can be a sender. A single-line telephone cannot be a
receiver for Individual Coverage and can be a receiver for Group Coverage only
when the single-line telephone is assigned as a member of a calling group.
The queued call console (QCC) queue can be a Group Coverage receiver and
is not counted in the maximum of eight receivers allowed for each group.
The QCC queue is not available in the Key and Behind Switch mode.
A maximum of eight Individual Coverage receivers (primary or secondary)
can be assigned for an individual sender.
A maximum of 30 coverage groups can be assigned.
The factory setting for type of calls covered for a sender is both inside and
outside calls.
Each coverage group can have from no members to the maximum number of
telephones in the system.
Each sender can be a member of only one coverage group.
A receiver with a multiline telephone can program one to eight Group Cover
buttons for an individual coverage group; however, each programmed button
is counted in the eight Group Cover button maximum.
A maximum of eight Group Cover buttons can be assigned for each
coverage group. All eight can be programmed on one multiline telephone, or
the Group Cover buttons can be distributed among up to eight multiline
telephones.
A receiver with a multiline telephone can provide coverage for a maximum of
eight coverage groups and/or individual senders.
When the QCC queue is programmed as a Group Coverage receiver along
with multiline telephones, the queue is not counted in the eight-receiver
maximum for each group. The QCC queue can provide Group Coverage for
1-30 coverage groups.