AT&T MERLIN LEGEND System Reference Manual page 542

Hardware
Music-On-Hold and the
Music Couple
5-36 Adjuncts
Background music can be provided for outside callers on hold or for selected
areas of a building over the loudspeaker system.
Note: If equipment is used that rebroadcasts music or other copyrighted
materials, the user may be required to obtain a copyright license from, and pay
license fees to, a third party such as the American Society of Composers,
Artists, and Producers (ASCAP) or Broadcast Music Incorporated (BMI). Or a
Magic on Hold™ system, which does not require the user to obtain such a
license, can be purchased from AT&T or an authorized dealer.
Music can be heard by outside callers on hold by connecting a music source or
Magic on Hold unit to a music coupler (see figure 5-21). The music coupler
must connect to a loop-start port that has been programmed for Music-on-Hold
(MOH) operation and must be used with an 8-ohm music source. The loop-start
port cannot be assigned to a trunk pool, cannot appear as a programmed line
on system telephones, cannot be connected to a loudspeaker paging system,
and cannot be on a trunk port assigned to the QCC queue or to calling groups.
When a call is transferred, it is automatically connected to MOH if the system
provides this feature.
The PagePac 20 also provides a music source for paging and MOH without a
music coupler.