Devices for IP telephony

By Christine Perey, |  Networking

In our
, we were talking about devices that can capture voice traffic and
immediately packetize it for transmission on a LAN or across the Internet. We noted
three types:

  1. A handset, headset, or tabletop microphone and speakers attached to a PC, with a
    keyboard and mouse interface;
  2. An adapter that mediates between an analog telephone and an IP network connection;
  3. A standalone IP- or IP/PSTN-ready telephone (PSTN is the public switched telephone
    network that connects ordinary telephones around the world)

The first category offers the greatest number of choices. VoIP product databases,
like Gecko
Research and Publishing's IpxStream
, href="">Jiri
Kuthan's list, and Internet Product Watch list dozens of software applications
for use with any Windows personal computer or Unix machine with access to an IP

The bulk of the software applications for VoIP are available for download on the
Internet. Some require payment if you decide to keep them. To be useful, the software
on your PC must register with some sort of directory, so that people calling you don't
have to enter your IP address every time they want to call you. The latter situation
would be especially awkward if, like most dial-up users, you have a new IP address
assigned each time you connect to the Internet.

With each application, all users register automatically in a common directory
service each time the application connects to the network, and the directory service
resolves addresses on behalf of users. Generally, these directory services are not
public in the way our PSTN directory assistance is accessible from any end point. They
are available only to subscribers and are populated only with information about other
subscribers using the same service.

With any software, you'll need a voice-capture device. A simple microphone and
speakers plugged into a sound card should work fine, but if you want more convenience
or privacy, you can connect a handset or headset instead. href="">Riparius Ventures offers a handset and href="">Andrea Electronics makes a popular
high-quality, PC-ready headset. Both are available in retail outlets and online

Options 2 and 3 above are emerging technology. There are a few products in these
categories, ideal for early adopters and more appropriate for the small- and home-
office markets than large enterprise deployments.

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