AT&T MERLIN LEGEND System Reference Manual page 239

Features
Callback
Call Waiting
Camp-On
Conference
Coverage
Direct-Line Console
Direct Station Selector
2-190 Group Calling
Calls made to a calling group are not eligible for Callback since the call rings
into the calling group's queue. However, Callback can be used for calls to
individual calling group member extensions or to the delay announcement
device. Calling group calls are not sent to the group member telephone when
the calling group member uses Callback for a busy extension or pool or if
another person used Callback to reach to calling group member and the
Callback call is ringing on that person's telephone.
Calls made to a calling group are not eligible for Call Waiting since the call rings
into the calling group's queue. However, call waiting can be used for calls to
individual members of the calling group. If the calling group member is a fax,
the Call Waiting tone is not given to the fax port.
Users can transfer calls to a calling group by using Camp-On, but calls do not
return to the originating telephone, even if it is not answered within the
programmed Camp-On Interval. If the calling group is made of fax machines,
the Call Waiting tone is not given to the fax port.
Calls waiting in the calling group queue or ringing at a calling group member's
station cannot be added to a conference call. A user must be connected to a
calling group member before the call can be added to the conference.
A calling group cannot be programmed as a receiver for Individual Coverage. A
coverage group can have a maximum of one calling group as a receiver. If a
calling group is programmed as a receiver for a coverage group, it can be the
only Group Coverage receiver individual Coverage (primary and/or secondary)
receivers can be programmed. A calling group can be a receiver for 1-30
coverage groups.
As soon as the call is sent from the calling group queue to a calling group
member, the call appearance is removed from the sender's telephone (except
for outside calls received on personal fines).
A calling group member can be a sender for Individual Coverage (Primary or
Secondary) or Group Coverage. Calls to the calling group extension number are
sent only to the calling group member's Individual Coverage receivers and not
to the Group Coverage receivers. Calls to the calling group member's individual
extension are sent to both Individual and Group Coverage receivers.
A DLC can be a member of a calling group and is normally used as the calling
group supervisor position.
The LED for a DSS button for calling group extension number indicates the
status of calls in the calling group queue. The LED is on when calls are at or
above the programmed threshold and off when below the threshold.