Page 352 - Asterisk™: The Future of Telephony

Inbound call to DID Passed to PBX

PSTN PRI/BRI/Analog PRI/BRI/Analog
Legacy PBX
Relayed out to
SIP/IAX/H323
Cell phone cell phone
Delivered to
home office PBX telephone
VoIP
IP telephone

Figure 15-2. Find-me-follow-me

PSTN PRI/BRI/Analog
PRI/BRI/Analog
Legacy PBX
SIP/IAX/H323

PBX telephone

VoIP
IP telephone
PRI/BRI/Analog
Connection to
remote Asterisk
Delivered to Remote PBX
remote PBX
Figure 15-3. VoIP-enabling a legacy PBX
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 15-3 shows how you can use Asterisk to VoIP-enable
a legacy PBX.

Low-barrier IVR
Many people confuse the term “Interactive Voice Response,” or IVR, with the Auto-
mated Attendant (AA). Since the Automated Attendant was the very first thing IVR was

324 | Chapter 15: Asterisk: The Future of Telephony