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Messaging Applications
Most PBX environments support a central, “big picture” application called an atten-
dant console. This application can monitor the status of calls in progress throughout
the PBX or within a certain scope of users, tell who’s on the phone and who’s not,
and sometimes even keep track of who’s in the office and who’s out of the office.
The console application may or may not have a phone directly connected. In some
systems, the console itself is an endpoint with a large, specialized display built in. In
others, it’s a PC application or terminal connected to a serial interface on the PBX.
In Asterisk, there isn’t a dedicated console application, but some people have used Ast-
man as a substitute for a homegrown console application. Cisco, Avaya, and Nortel
provide PC-based or web-based console applications for their softPBX systems.
In-Out, DND, and Call Forward
Many traditional PBX systems offer endpoints with an in-out function—that is, the
endpoint can be used to alert the console when an office occupant is in or out of
their office. That way, the human attendant, who uses the console, will better know
how to handle that user’s calls.
Do not disturb, or DND, is another PBX endpoint function that allows each user to
silence the ringer on her phone, placing it in a state of silence so incoming calls don’t
disrupt the user’s activities.
Call forward gives PBX endpoints the ability to temporarily relay all incoming calls to
another endpoint, either on the same system or, if the PBX supports it, on the PSTN.
On the public switched telephone network, SS7 facilitates signaling of
all advanced calling features, called CLAS (custom local area calling
services). These include call-waiting, a form of hold with two line
appearances, and three-way calling, a three-party conference call.
Call Logs and Missed-Call Indications
Some PBX endpoints and caller ID–equipped analog phones can store a log of calls
placed, received, and missed. This feature tends to be something built into the end-
point, though the same information is almost always stored in the PBX’s call
accounting system.
Messaging Applications
Telephony messaging applications are one-way in nature, distinguishing them from
call-handling applications. That is, a message is sent from one party to another, and
unlike a two-way phone call, the receiving party cannot respond in the same medium

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