AT&T MERLIN LEGEND System Reference Manual page 150

Features
System Programming
Related Features
Assign extensions to Group Coverage sender groups.
Extension -> More -> Group Cover
Assign calling group as a Group Coverage receiver.
Extension -> More -> Grp Calling
Assign or remove principal user of a personal line. This specifies that calls
received on the personal line follow only the individual extension's Coverage
patterns and not the Coverage patterns of other users who share the line. In
addition, if Remote Call Forward is assigned, calls received on the personal
line can be forwarded to outside telephone numbers.
LinesTrunks -> More -> PrncipalUsr
Change the number of rings programmed for the Delayed Ring Interval (1-6
rings; the factory setting is 2 rings).
Options -> Delay Ring
Change the number of rings programmed for the Coverage Ring Interval
(1-9 rings; the factory setting is 3 rings).
Options -> More -> Cover Delay
Group Pickup
Ringing Options
-> Coverage
Coverage 2-101