AT&T MERLIN LEGEND System Reference Manual page 149

Features
Ringing Options
Station Message Detail
Recording
System Access
Transfer
2-100 Coverage
Primary Cover, Secondary Cover, and Group Cover buttons can be
programmed for Immediate Ring, Delayed Ring, or No Ring. If an Individual or
Group Coverage receiver is on a call when a coverage call is received, the
receiver hears an abbreviated ring (if Abbreviated Ring is enabled). Calls
received on a Primary Cover, Secondary Cover, or Group Cover button ring with
the receiver's (not the sender's) personalized ringing pattern.
The extension of the telephone on which an Individual or Group Coverage call is
answered is shown on the SMDR report.
When a Primary Cover, Secondary Cover, or Group Cover button is
programmed, a call received on an Intercom or System Access button that is
eligible for Individual or Group Coverage remains on the sender's Intercom or
System Access button until it is answered at the receiver's telephone. However,
in the Hybrid/PBX mode, calls received on Shared System Access buttons are
not eligible for Individual or Group Coverage.
Once answered by a receiver, the call is removed from the sender's Intercom or
System Access button (including all Shared System Access buttons). However,
when a calling group is programmed as a Group Coverage receiver, the call is
removed from the sender's telephone as soon as it is sent from the calling group
queue to an available member.
In the Hybrid/PBX mode, if a receiver programs a Primary Cover, Secondary
Cover, or Group Cover button for a sender and also has a Shared System
Access button associated with the sender, the green LED next to both the Cover
button and Shared System Access button flashes. The red LED stays on at the
Shared System Access button it does not automatically go on next to the Cover
button.
Calls transferred to a sender are eligible for Individual and/or Group Coverage.
However, the sender hears a Call Waiting tone if the sender is using Coverage
On/Off to prevent calls from going to coverage and does not have an available
Intercom or System Access button to receive a transferred call, even if an
Individual or Group Coverage receiver is available.
A call answered on a Primary Cover, Secondary Cover, or Group Cover button
can be transferred. When One-Touch Transfer is programmed, the call can be
transferred by using DSS buttons. Transfer returns are not eligible for Individual
or Group Coverage.