Prior to Unity 3.0(1), each subscriber in Unity can be associated only with a single exten-
sion called the primary extension. This proved to be a big limitation that customers com-
monly ran up against. Several customers desired a way for a device such as a cell phone to
forward unanswered calls to Unity and for Unity to integrate the call to the same mailbox
of the subscriber. Tricky routing rules should allow this; however, they really did not scale
as a solution. The limitations forced the development of a new solution called alternate
extensions.
An alternate extension is just an extensions ...
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