Making a VoIP Call – Soft VoIP Phones

There are several ways to make VoIP calls. You can sign up with a VoIP service provider and use your existing telephone equipment, or you can use a software package (sometimes called a 'Soft Phone') that allows you to connect to other computers or landline phones.

VoIP software such as Skype or Gizmo allows you to try out VoIP without investing in extra equipment or signing a contract that ties you in with a specific VoIP provider. All you need is a sound card and a headset with a microphone and headphones. You could also use an Internet telephone that plugs into the sound card or USB port on your computer.

VoIP software seems to be the latest craze -- there are at least 50 companies offering their own version of VoIP. Some of them are for specific computer platforms like Linux but others can be used on many kinds of computers and operating systems. They allow you to make free computer-to-computer calls but you have to pay a small fee if you wish to connect to the regular phone networks (PSTN - Public Switched Telephone Network or also called POTS – Plain Old Telephone Service).

Up until recently, the major disadvantage with computer-to-computer calls was that both parties had to have the same kind of software installed in order to make a connection. The emerging SIP (Session Initiation Protocol) standard, however, allows any SIP software to connect. Some software does not use SIP - Skype, for example, uses a proprietary protocol and cannot connect to other types of software. Almost every software package, however, has the ability to connect with landline or cellular phones.

Soft phones can be used anywhere in the world where a broadband Internet connection is available. You can call a business associate in Asia or your cousin Charley who lives down the street as long as both have the proper software installed.

How Soft VoIP Phones Works

Although each VoIP software package has its own unique interface they are all similar in function. You usually call another person on the network by typing in their user name or number. If that person is online they will see a popup box alerting them that you want to talk. The other party can see who is calling and can either accept or reject the call.

Before the popup appears, however, there has already been some communication between the two computers. The VoIP software has information about the speed of your Internet connection and the type of codec that can be used to compress and decompress audio data. When a call request is made, both computers have to negotiate which codec is going to be used to make allowances for the connection speed.

The first step in making a computer-to-computer telephone call is to convert your voice into digital data. As you speak into the microphone of the headset or telephone set connected to your computer, it is 'sampled' -- converted to digital numbers by dividing the analog signal into individual steps, each of which are given a numerical value. This is the same technology behind audio CDs which convert analog signals into digital data by sampling the sound 44,100 times per second.

CD-quality sound, however, is not needed for Internet telephony. Voice data can be compressed substantially and still remain understandable. For example, the single word 'Hello' requires about 43 kB in CD-quality sound. Compression algorithms can bring that down to about 2 kB!

The compressed voice data is encapsulated in data packets which will be sent over the Internet. The destination of the data is encoded in each packet, but the route each packet takes may be completely different from other packets in the same data stream.

The Internet is made up of thousands of 'Routers' which are responsible for delivering data in an efficient manner. Routers have information about the data load of other routers in the network and can use this information to determine the fastest path. The router examines the destination address of each packet and forwards it to the next router on the path. In this manner, the data packet is forwarded from router to router until it reaches its destination.

Since the conditions of data paths along the Internet are constantly changing the most efficient path for one data packet may not be the same for the next packet. This means that VoIP data will probably not arrive at its destination in the same order that it was sent. The data can be reconstructed in the proper order because each packet has a time stamp on it, but in order to minimize the delay between one person speaking and the other person hearing the voice, some of the packets may have to be dropped.

The quality of the connection depends in part on how many packets are dropped. This in turn depends on the speed of the Internet connection at each end and the general condition of the Internet pathways.

Once the data has been received it is converted back into an analog voice signal with the Analog to Digital Converter (ADC) on the sound card or telephone set.

Making a VoIP Call – Connecting PSTN and VoIP

A step up from computer-to-computer telephony is calling regular landline or cellular phones from your computer. Usually, the same software package that allows you to make PC-to-PC calls allows you to call to the regular phone networks at a small charge.

Before making this type of call you need to fill your account with credits. Most VoIP companies allow you to add credit with your credit card or a payment system like PayPal.

To call a landline or cellular phone from your computer just dial the number. Software like Skype and Gizmo have onscreen keypads that you can use with a mouse or you can use the keypad on your computer keyboard or Internet phone. Don't forget to include the area code or country code if you're calling long distance.

A 'gateway' makes the connection between the Internet and PSTN (Public Switched Telephone Network). Because gateways can be situated locally the costs associated with long-distance phone calls are minimized. In fact, the cost may be the same whether you are calling locally or across the globe.

Gateways have been used for quite a number of years to provide low-cost long-distance calls. You may belong to a plan which offers tremendous savings over the long-distance rates of your local phone company. Companies which offer these low long-distance rates are using Internet telephony. Because their costs are so much lower, they can pass the savings on to the consumer. By making computer-to-telephone calls you are using the same technology as these long-distance phone companies.

Computer-to-telephone is fine for making outgoing calls, but what do you do if you want to receive calls at your computer? Once again, the latest technology comes to your rescue.

Some VoIP companies can provide you with an incoming phone number in a particular city. When someone dials that number the call will be routed to your location, no matter where in the world you are. The cost of the call is the same as a regular call to the city your number is located in.

As an example, if your incoming telephone number is based in New York City and your friend calls you from New York, it will be treated as a local call even if you are in Hong Kong at the time. However, somebody calling from Los Angeles will have to pay the long-distance charges that apply to any regular call from Los Angeles to New York.

These local phone numbers are available in a number of cities in North America and also in Europe and Asia depending on the VoIP provider. It makes sense to choose a local location where most of your incoming calls are originating from to allow people to call you at a minimum expense.

You can receive calls anywhere in the world where a broadband Internet connection is available. Simply login into your account to make and receive calls from your laptop or an Internet café using a headset or Internet telephone. Some VoIP software even allows you to use a PDA (Personal Digital Assistant) as a telephone.

Making a VoIP Call – VoIP Equipment

Above we examined VoIP using computers. Internet phone calls can also be made without a computer. A broadband Internet connection is still required but it doesn't need to be connected to a computer to take advantage of VoIP.

This kind of system works by installing a broadband modem to a telephone or cable TV line. The modem is attached to a regular telephone with an Analog Telephone Adapter (ATA). These devices are usually provided free of charge when you sign up with a VoIP service provider.

The ATA is connected to the modem and provides the necessary hardware and software to convert your analog voice signal into compressed digital data. The person receiving the call does not need any special equipment and will have no indication that you are not using PSTN (Public Switched Telephone Network). In fact, in some situations, the signal may be clearer than with land-based phone lines.

One of the great advantages of having an ATA is its portability. The ATA is a small, lightweight device that can be taken with you anywhere. Why would you want to do this? If you have access to a broadband modem anywhere in the world, you can simply plug a regular telephone into your ATA and connect it to the modem. The ATA has a unique identification number that allows people to call you no matter where in the world you are. The cost of such a call is the same no matter whether you are in Hong Kong or Toronto.

If the idea of carrying around an ATA seems cumbersome, you can buy an IP phone that combines the phone set and the ATA into one unit. IP phones are plugged into a modem and can be used to make or receive calls anywhere in the world.

As an example, suppose you are based in San Francisco and are travelling in Asia. Anybody can call your regular San Francisco phone number and their call will be routed to your IP phone in Hong Kong or Tokyo or wherever you are. If they are calling from San Francisco there are no overseas charges involved. Similarly, if you want to call someone in San Francisco, your call will be treated as a local call.

All the extra features of VoIP are available with both ATA's and IP phones. Call waiting, call forwarding, call display, and conference calls can all be done with either an ATA or an IP phone. The cost of these services is usually included in your monthly rate – a substantial saving over similar services offered by your traditional phone company.