|With Callback, a user does not have to repeatedly call a busy extension back, hoping to ﬁnd it idle.|
An extension user can leave a Callback at many extensions simultaneously. The system processes the Callbacks as the extensions become free. In addition, many extensions can leave a Callback at the same extension. The system processes these Callbacks on a ﬁrst-in/ﬁrst-out (FIFO) basis.
If an extension user leaves a Callback request and then fails to answer within four rings, the system cancels the Callback.
If an extension is set up to receive Camp-On tones for Intercom calls, and Camp-On tones are enabled system-wide, it will receive the tones when a user leaves a Callback.