AT&T MERLIN LEGEND System Reference Manual page 377

Features
Transfer
System Programming
2-328 Ringing Options
The principal station in a shared System Access arrangement can activate Send
Ring, which causes any Shared System Access button on other telephones that
are programmed with Delay Ring to ring immediately when the principal station
user is on the telephone. The feature can be activated or canceled by the
principal station user.
Transfer returns ring until answered and do not receive Abbreviated Ring.
Change the number of rings programmed for the Delayed Ring Interval for
Primary Cover, Secondary Cover Group Cover buttons programmed for
delayed ring (1-6 rings, the factory setting is 2 rings).
Options -> Delay Ring