System information

Here are some of the options you can implement:
Keep your old PBX, but evolve to IP
Companies that have spent vast sums of money in the past few years buying pro-
prietary PBX equipment want a way out of proprietary jail, but they can’t stomach
the thought of throwing away all of their otherwise functioning equipment. No
problem—Asterisk can solve all kinds of problems, from replacing a voicemail
system to providing a way to add IP-based users beyond the nominal capacity of
the system.
Find-me-follow-me
Provide the PBX a list of numbers where you can be reached, and it will ring them
all whenever a call to your DID (Direct Inward Dialing, a.k.a. phone) number
arrives. Figure 27-2 illustrates this technology.
VoIP calling
If a legacy telephony connection from an Asterisk PBX to an old PBX can be es-
tablished, Asterisk can provide access to VoIP services, while the old PBX continues
to connect to the outside world as it always has. As a gateway, Asterisk simply
needs to emulate the functions of the PSTN, and the old PBX won’t know that
anything has changed. Figure 27-3 shows how you can use Asterisk to VoIP-enable
a legacy PBX.
Low-barrier IVR
Many people confuse Interactive Voice Response (IVR) systems with automated at-
tendants (AAs). Since the automated attendant was the very first thing IVR was used
for, this is understandable. Nevertheless, to the telecom industry, the term IVR repre-
sents far more than an AA. An AA generally does little more than present a way for
Figure 27-1. Asterisk as a PBX gateway
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