Switching to VoIP

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Chapter 5: Enterprise Telephony Applications

Intercom Call

Intercom calling is the oldest of all telephony applications. In fact, it was the inter-

com calling application that lead to the invention of the telephone. This one tele-

phony application came even before the network did. When Alexander Graham

Bell’s assistant heard the inventor’s voice coming through a transducer, quite by acci-

dent, the first intercom call was placed.

An intercom call is merely a conversation between two private endpoints. Most inter-

com calls are two-way conversations, meaning both parties can talk and hear each

other talk. In PBX terms, intercom calls are calls between extensions. The setup in

Project 4.2 allows you to place intercom calls between the two IP phones.

Mute, Hold, Call Transfer, and Multiparty Conference

Certain features have become more or less staples of a PBX environment. Mute

allows the local party to temporarily stop sending sound to the remote party. Hold is

a form of mute that allows the local party to leave the phone set for an extended

period of time, unattended, and then return to resume the conversation with the

remote party. Call transfer allows the local party to hand the call in progress off to

another extension, so it can be resumed there. Multiparty conference allows