Switching to VoIP

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Chapter 12: PSTN Trunks

But with a little bit of dial-plan setup on each of the two PBXs and a few PSTN

trunks dedicated to the task, it’s possible to allow users at the East office to dial users

at the West office by their four-digit extensions. Each office will need a minimum of

one PSTN trunk for this to work. Larger setups that require more concurrent calls

will need more PSTN trunks. Project 12.2 explains how to set up four-digit dialing

between PBX systems at different offices, making the convoluted process in

Figure 12-6 disappear.

Project 12.2. Use PSTN Trunks in a Multioffice Dial-Plan

What you need for this project:

• Two or more Asterisk servers

• Two X100P interface cards (one in each server)

• Two SIP soft- or hardphones

• LAN

In keeping with the example illustrated in Figures 12-5 and 12-6, we can build a two-

office unified dial-plan using two Asterisk servers. This way, users need dial only the

extension of the user at the other office in order to reach her. Asterisk will then route

the call to the other office’s PSTN trunk, wait until it’s answered, and dial the recipi-

ent’s extension in order to complete the connection.

We’re assuming here that we have two Asterisk servers—East and West. We’ll use

the same dial-plan extension numbering convention as in Figure 12-6. ...