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VoIP Phones

This page describes the VoIP phones, its types, how it works and its advantages and disadvantages. Click on any of the following links to get to the corresponding answer.
For more technical details read through VoIP technology.

 

What is a VoIP phone?

VoIP means Voice over Internet Protocol. VoIP phones (or Digital Phones) send voice data in packets over the IP layer. The services they provide are typically the same as the normal phones but the underlying network and the technology are different.

  • It might be a dedicated device (like the traditional handset) using IP connection.
  • It can also be a normal phone connected to the network through a telephony adapter (TA).
  • Else it can be a softphone.

What is an Internet phone?

An Internet Phone is a VoIP phone that uses the public Internet to send voice traffic. Most VoIP phones can be used as an Internet Phone with a little tweaking. However first-generation Internet phones such as the PingTel Expressa have been on the market since 2001.

What is a SIP phone?

Typically, an Internet Phone uses the Session Initiation Protocol (SIP) or Media Gateway Control Protocol (MeGaCo). A VoIP phone based on SIP is called a SIP phone. You can have a basic introduction on SIP.

What is a softphone?

A softphone is a software that runs on a general purpose computer instead of a dedicated device. It simulates the experience of a normal phone with the aid of a headset or a USB device. These use different implementation techniques. They might use standard protocols like SIP or H.323 or a proprietary one.
The most typical SIP-based soft phones as of today include - eyeBeam from CounterPath (formerly Xten), OpenWengo, Nexge, sipXphone, Adore Softphone, Express Talk and SJphone.
Applications like Skype, Google Talk or Yahoo Messenger use proprietary environments of their own. They are not intercompatible.

What do I need to use a VoIP phone?

  1. You need an Internet Connection, a good one, preferably broadband.
  2. You need to register with a ITSP (Internet Telecom Service Provider). You can have a look at the list of ITSP.
  3. If you want to use your older telephone, you need a telephony adapter (TA) to connect the analog phone to the digital network.
  4. Instead of (3) you might take a new voip phone or use a softphone.

How does a VoIP phone work and how is it different form a normal phone?

VoIP uses an IP based network over which it transmits voice data in the form of packets. Normal phones send analog signals over a switched network (PSTN: Public Switched Telephone Network), which is specifically designed for voice transmission. For a more detailed discussion on the technology, have a look at VoIP technology. Some differences between the VoIP phones and the traditional phones will be clearer as you go through the advantages and disadvantages of VoIP phones.

What are the advantages of VoIP phones?

  • Low cost. Calls over the internet are generally free. That means you can call anyone anywhere in the world just like sending emails. However, the cost for the internet usage is there. There are charges for calling PSTN phones but long distance calls are in general cheaper than traditional landline connections.
  • You can just plug your device anywhere, e.g. in a hotel room and it works as if you are at home. Your number remains the same. There is no roaming cost unlike your mobile phone connection.

What are the disadvantages of VoIP phones?

  • If you donot have a good internet connection, rather stay away from voip. People have mixed feelings. Some report to have used voip comfortably over dial-up connections, some complain that they had bad experiences even over DSL. To be on the safe side, you need a reliable connection with good uplink bandwidth.
  • The device or the modem through which you connect to the network needs power, either from battery or directly from the line. This might pose a problem where there are frequent powercuts.
  • Number portability if you are switching from a regular phone. Some providers might not even support number portability, some might take considerable delay for the process.
  • Reliability of the system is under doubt as Internet was not designed for real-time services like voice.
  • Support for 911 is not well-defined. Some voip service providers do have support for the emergency number but the way the emergency call is handled might be different from one operator to other.
In spite of the points discussed here, voip telephony has a future. The problems will get solved gradually. However, it is unlikely that voip telephony will take over the PSTN system overnight.

What are the ITSPs (Internet Telephony Service providers)?

The complete list might get pretty long, even longer with more service providers coming up each month. Here is a short list.

For a comprehensive list have a look at http://www.iptelephony.org/GIP/providers/.

For more technical details read through VoIP technology.



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© 2005 K.Banerjee
Last updated: February 06, 2006