Tuesday, March 15, 2005

Softphones Turn Computers Into VoIP Telephones

Telephones are for voice and computers are for data, right? Well, that's the way it used to be. That was back when telephones had their own network, the Public Switched Telephone Network (PSTN). Computers had their own network, the Internet. Then along came cellular phones that download email and web pages, and VoIP phones that let you talk over the Internet. Now you can mix and match almost to your heart's content.

Softphones are blurring the line between telephone and computer even further. A softphone is a telephone in software. It pops up on your computer screen and you make phone calls with it. You can even make phone calls while you are surfing the web or sending email with your computer.

That suggests some interesting possibilities. Download a softphone into your notebook computer and you have VoIP to go. You can take your regular VoIP phone service with you on business trips and vacations. All you need is a hotel, coffee shop or airport lounge that offers broadband access. There are no telephone roaming charges like you have with cellular because one access point is as good as another on the Internet. If you have an unlimited calling plan, there are no additional telephone charges no matter where you are. It even works overseas where you can get broadband access.

Say you are an independent sales agent. Set yourself down in a cafe that offers free WiFi, order up a cappuccino, and you can talk to your customers, look up information and even enter orders at your corner table. Or, drop by to see clients with your entire office tucked under your arm.

So how DO you turn a computer into a telephone? The softphone client is a program like a browser or email program. Part of it establishes a link to your Internet connection to transmit and receive VoIP formatted voice packets. Another part uses the sound card within your computer to convert from microphone audio to digital words, and to speaker audio from incoming digital words. This is called analog to digital (A/D) and digital to analog (D/A) conversion. Some computers have a separate digital signal processor (DSP) chip to do this. Many use an Audio Codec (Coder/Decoder) chip and signal processing software that runs on the computer's microprocessor.

Other parts of the softphone client handle signaling with your VoIP provider and create a graphical user interface on your screen that looks and operates much like any other phone. You get the usual controls, such as a keypad, dial and hang up buttons, microphone and speaker volume controls, special buttons for mute, call transfer and conference, phone book access and a call display. The display shows such things as your call status, dialed number, caller ID info and a call timer.

You can use the speaker and microphone that are built into your computer to make calls, but that's a lot like using a speakerphone and you might have echo problems. Softphones work a lot better when you use a headset with a separate microphone and earpiece. Just plug the connectors into your computer audio jacks.

One important point about softphones is that they have really gained popularity only since the widespread availability of broadband Internet access. PC to Phone software was available for dial-up connections, but it was often disappointing to use. The slow 56K bitrate combined with earlier computers that had slow processors and limited memory often resulted in poor audio quality and breakups in the conversation. You'll want at least 128 Kbps upload and download speed, even though some codecs may work at lower rates. That's especially true if you are going to use your computer as a computer while it is also being a telephone.

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