VoIPowering Your Office with Asterisk: Hardware Mysteries Explained

It's fun and useful to explore pure IP telephony, but most folks want PSTN (Public Switched Telephone Network) integration as well. (PSTN is also known as POTS: Plain Old Telephone Service.) An Asterisk server can interface with "legacy" systems, which means "not IP," or your ordinary old digital and analog telephone systems.

 

Digium Inc., the inventors and sponsors of Asterisk, make legacy interface hardware. Other popular brands are Sangoma, VoiceTronix, and Cisco. There are dozens of different vendors, as most networking hardware manufacturers have added VoIP devices to their product lines. I'll use Digium's products as examples. These require the Zaptel drivers, which you can download from asterisk.org, and the Linux operating system—because the Zaptel drivers only work on Linux.

Other operating systems can use standalone media gateways. "Media gateway" is a broad term that includes both devices for servers, and devices for individual telephones. You can use a media gateway with your Linux system, rather than installing interface cards in your Asterisk server. Analog interfaces An Asterisk server plugs nicely into an existing analog phone network.

Just add an adapter like Digium's TDM2400P. This connects to your existing punch block with a standard 25-pair telco cable and connector. Now you have a powerhouse PBX that can do just about anything, for a fraction of the cost of a traditional PBX. The TDM2400P cards cost from around $600 to $1,700, depending on how they are configured. You may use the TDM2400P to connect your existing analog phones to your VoIP network, which allows you to replace them with IP phones on a timetable that suits you. Or never replace them, whatever fits into your master plan.

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Written by Dal on July 10th, 2006 with no comments.
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