Have you heard that
you can make a telephone call over the Internet? It's called Voice
Over Internet Protocol, or VoIP. This is how it works. You first
need a high speed Internet connection such as a cable modem or DSL.
You then attach an adaptor that connects your high speed connection
to your telephone and simply pick up the phone and dial. The phone
call goes over the Internet to the person you are calling. If
someone calling you, your phone will ring, just like a regular call.
Why consider VoIP? Simply put - Cost. If you already have a high
speed Internet connection, you no longer need to pay the additional
cost for a line just to make telephone calls. Also, some Internet
calling plans may offer features and services that are not available
with traditional telephone service. There are already a number of
companies offering VoIP services. These companies have the
equipment to connect your telephone to your existing high speed
Internet connection. Different companies offer different calling
plans, features and services. You can find more information by going
visiting links (see the green boxes on the left side) on the web and
comparing prices and service plans. Voice over Internet Protocol
(VoIP) adds another choice for consumers. Take a look at it! It just
may save you money. Click here for more information.
Consumers and businesses alike will come to appreciate the
low monthly rates, useful features, and clear voice
quality of an Internet phone service. We reviewed six such
services and found one clear winner.
doubt you're familiar with the company, but its
competitors offer better features and lower rates.
BroadVoice adds 911 support, this otherwise
feature-rich Internet phone service is best used
as a second line, despite its cheap rates.
Until a couple of key features
are added, we suggest you hold off on Broadvox's
otherwise excellent service.
iConnectHere will save you money
on your long-distance bill if you can live without
consistent call quality and 911 support.
offers low rates that will appeal especially to
international callers, but its call quality is
inconsistent compared to some VoIP services.
Flat-rate international calling
plans, a videophone option, and low rates make
Packet8 a good choice, but only as a second line.
You'll find slightly better rates
elsewhere, but Vonage offers an unmatched feature
set and consistent call quality.
Voiceglo offers clear calls and
reasonable monthly rates but lags behind its
competitors in the number of features it provides.
takes traffic management to the next level by
reducing WAN costs and improving application
response times automatically.
WebPhone is a
voice over Internet Protocol (VoIP) service that
helps you lower your phone bills.
Pronexus is a
full-service communications company that delivers
award-winning solutions for business-critical CT
Diva Server Voice provides an ideal platform for a
VoIP gateway solutions providing all relevant
features for best voice quality.
Access211, voice over IP (VoIP) media gateway,
enables service providers to provide their
residential and small office home office (SOHO)
customers with high-quality VoIP service using
traditional analog telephones and fax machines.
powerful suite of hosted VoIP solutions enable
service providers and distributors to provide high
quality, low cost, domestic and international long
distance calling to enterprises and consumers
around the world.
of VOITSP Inc. offers the most advanced high
quality Voice Over Internet Protocol technology
and services, fresh out of our strong Research and
RAD offers an
impressive array of access product solutions to
serve the technological and business requirements
of service providers, carriers and enterprises.
RAD solutions reduce infrastructure and
operational costs while boosting competitiveness
and profitability - even as companies begin to
migrate to future network architectural models,
such as IP/MPLS.
service brings the power of Voice over IP to the
home. Whether you would like a SoftPhone running
on your PC or one-line units that connect your
home telephone to the internet, we can provide it
all at unbeatable rates. All you need is an
internet connection and you're ready to
multimedia, & VOIP services with solutions
TalkBroadbandTM is a revolutionary new technology
for your business that transforms your High Speed
Internet Service into a phone line - without
replacing your phone system, or your existing
phone number.With TalkBroadband service from
PRIMUS Canada,you can call other offices,
suppliers, and clients without a single long
distance charge. All you have to do is start
talking and you'll save.
All of our phones
support the SIP standard and are compatible with
most SIP-based phone systems such as The VoIP
Connection VS-1, Zultys MX250 and Asterisk. Our
phones also work great with SIP-enabled phone
services including Free World Dialup, SIPphone and
beginning of the end of long distance charges in
Canada" You can now call coast-to-coast to
any 'Canadian Village' city as a 'local' call. A
call from Montreal to Vancouver or Kitchener to
Toronto is now the same as a call from Montreal to
V2oIP® ENSEMBLE SIP Solutions consist of a
versatile set of tools for development, testing,
and validation. Designed for developing and
testing all types of SIP-based applications, the
SIP development solutions provide the highest
level of compliance with the latest IETF standards
including RFC 3261 and related standards.
is a resource uniting various projects on
Telecommunications and Voice over IP, Hosting and
Colocation services, Hardware and Software
products, as well as Cables and Satellites around
All the VOIP
Brands All the VOIP, All the Savings! Smart VOIP
Shoppers Start Here.
The WiFon Headset
and USB Handy work with any software phone
dialer.The WiFon LAN is a network-ready VoIP desk
phone.WiFon Mobile is a WiFi VoIP phone that
connects to the Internet at Hotspots.The WiFon
Switch connects an existing analogue telephone to
powerful and validated protocol stacks, SOLINET
gateways allow the interconnection of various
types of network for both the signalling and the
Communications is a global telecommunications
company that began providing Voice over Internet
Protocol service to users worldwide through
independent marketing representatives (IMR's).
without any commitment - immediately. Use SIP or
IAX2 to send toll free calls to anywhere in the
United States or Canada.
phonecalls over the Internet using your broadband
connection with our Virtual Centrex VoIP (Voice
over IP) phone service
Voice, also known as Voice over Internet Protocol
(VoIP), is a technology that allows you to make
telephone calls using a broadband Internet
connection instead of a regular (or analog) phone
line." FCC, 2004
fact is that VoIP will bring faster, easier
convergence between data and voice and eradicate
the 'application-advantage' that the bigger
organisations have always held over more modestly
sized companies. In bottom line terms, VoIP will
make your business run more efficiently, will give
you an 'edge' over your competitors and will
eliminate the technological advantage held by the
What's so good
about aql VoIP? Signup is free - including your
own 0870 number to receive inbound calls. Receive
landline to PC calls free.
Free voicemail and voicemail forwarding as .wav
file email attachments.
Whether you are a
brand loyalist interested in learning about what
else your favorite brand manufactures or want to
access all online retailers of a product to search
for the best deal; an all the Brands search is the
place where smart shopping starts. Popular brands:
Avaya, Lingo, Packet8, Vonage, Go2Call.com,
What is VoIP ?
Internet Voice, also known as Voice
over Internet Protocol (VoIP), is a technology that allows you to make
telephone calls using a broadband Internet connection instead of a
regular (or analog) phone line. Some services using VoIP may only allow
you to call other people using the same service, but others may allow
you to call anyone who has a telephone number - including local, long
distance, mobile, and international numbers. Also, while some services
only work over your computer or a special VoIP phone, other services
allow you to use a traditional phone through an adaptor
back to top
Internet Voice, also known as Voice over Internet
Protocol (VoIP), is a technology that allows you to make telephone calls using a broadband Internet
connection instead of a regular (or analog) phone line. Some services using VoIP may only allow you to
call other people using the same service, but others may allow you to call anyone who has a
telephone number - including local, long distance, mobile, and international numbers. Also, while some
services only work over your computer or a special VoIP phone, other services allow you to use
a traditional phone through an adaptor.
How VoIP / Internet Voice Works
VoIP converts the voice signal from your
telephone into a digital signal that travels over the Internet. If you are calling a regular phone
number, the signal is then converted back at the other end. Internet Voice can allow you to
make a call directly from a computer. If you make a call using a phone with an adaptor,
you'll be able to dial just as you always have, and the service provider may also provide a
dial tone. If your service assigns you a regular phone number, then a person can call you
from his or her regular phone without using special equipment.
What Kind of Equipment Do I Need?
A broadband Internet connection is required to make VoIP calls. Some services allow you to use a regular telephone, as long as you connect it to an adaptor. Some
companies allow you to make calls from a computer or a VoIP phone that doesn't require
an additional adapter. If you are calling a regular telephone number, the person you are
calling does not need any special equipment, just a phone.
If I have VoIP Service, Whom Can I Call?
Depending upon your service, you might be
limited only to other subscribers to the service, or you may be able to call any phone number,
anywhere in the world. The call can be made to a local number, a mobile phone, a long
distance, or an international number.
What Are Some Advantages of VoIP?
Because VoIP is digital, it may offer features
and services that are not available with a traditional phone. If you have a broadband
Internet connection, you need not maintain and pay the additional cost for a line just to
make telephone calls.
Does My Computer Have to be Turned On?
Not if you are making calls with a phone and
adaptor or special VoIP phone, but your broadband Internet connection needs to be
active. You can also use your computer while talking on the phone.
Is There a Difference Between Making a Local Call and a Long Distance Call?
Some VoIP providers offer their service for free,
normally only for calls to other subscribers to the service. Some VoIP providers charge for a long
distance call to a number outside your calling area, similar to existing, traditional
wireline telephone service. Other VoIP providers permit you to call anywhere at a flat rate for a fixed
number of minutes. Your VoIP provider may permit you to select an area code different from the area in which you
live. This means that if your provider charges for long distance, then charges could be based
on whether you call within your area code rather than geographic area. It also means that people
who call you may incur long distance charges depending on their area code and service.
Can I Take My Phone Adapter With me When I Travel?
You may be able to use your VoIP service
wherever you travel as long as you have a
broadband Internet connection available. In that
case it would work the same as in your home.
How Do I Know If I have a VoIP Phone Call?
The phone will ring like any other call.
Does the FCC Regulate Internet Voice?
The Federal Communications Commission
(FCC) has worked to create an environment promoting competition and innovation to benefit
consumers. Historically, the FCC has not regulated the Internet or the services provided
On February 12, 2004, the FCC found that an
entirely Internet-based VoIP service was an
unregulated information service. On the same
day, the FCC began a broader proceeding to
examine what its role should be in this new
environment of increased consumer choice
and what it can best do to meet its role of
safeguarding the public interest.
If you're considering replacing your traditional
telephone service with VoIP, there are some possible considerations you should be aware
. Some VoIP
services don't work during power outages and the service provider
may not offer backup power;
. It may be
difficult for some VoIP services to seamlessly connect with the 911
emergency dispatch center or to identify
the location of VoIP 911 callers;
providers may or may not offer directory assistance/white page listings.
also known as Voice over Internet Protocol (VoIP), is a technology
that allows you to make telephone calls using a broadband Internet
connection instead of a regular (or analog) phone line. Some
services using VoIP may only allow you to call other people using
the same service, but others may allow you to call anyone who has a
telephone number - including local, long distance, mobile, and
international numbers. Also, while some services only work over your
computer or a special VoIP phone, other services allow you to use a
traditional phone through an adaptor.
What is VoIP/Internet
VoIP allows you to make telephone calls using
a computer network, over a data network like the Internet. VoIP
converts the voice signal from your telephone into a digital signal
that travels over the internet then converts it back at the other
end so you can speak to anyone with a regular phone number. When
placing a VoIP call using a phone with an adapter, you'll hear a
dial tone and dial just as you always have. VoIP may also allow you
to make a call directly from a computer using a conventional
telephone or a microphone.
How Can I Place a VoIP Call?
Depending on the service, one way to place a
VoIP call is to pick up your phone and dial the number, using an
adaptor that connects to your existing high-speed Internet
connection. The call goes through your local telephone company to a
VoIP provider. The phone call goes over the Internet to the called
party's local telephone company for the completion of the call.
Another way is to utilize a microphone headset plugged into your
computer. The number is placed using the keyboard and is routed
through your cable modem.
hat Kind of Equipment Do I Need?
A broadband (high speed Internet)
connection is required. This can be through a cable modem, or
high speed services such as DSL or a local area network. You can
hook up an inexpensive microphone to your computer and send your
voice through a cable modem or connect a phone directly to a
Is there a
difference between making a Local Call and a Long Distance Call?
Some VoIP providers offer their
services for free, normally only for calls to other subscribers to
the service. Your VoIP provider may permit you to select an area
code different from the area in which you live. This means you may
not incur long distance charges if you call a number in your area
code regardless of geography. It also means that people who call you
may incur long distance charges depending on their area code and
Some VoIP providers charge for a
long distance call to a number outside your calling area, similar to
existing, traditional wireline telephone service. Other VoIP
providers permit you to call anywhere at a flat rate for a fixed
number of minutes.
If I have
Internet Voice service, who can I call?
Depending upon your service, you might be limited only to other
subscribers to the service, or you may be
able to call any phone number, anywhere in the world. The call can
be made to a local number, a mobile phone, to a long distance
number, or an international number. You may even utilize the service
to speak with more than one person at a time. The person you are
calling does not need any special equipment, just a phone.
Some Advantages of Internet Voice?
Because Internet Voice is digital, it
may offer features and services that are not available with a
traditional phone. If you have a broadband internet connection, you
need not maintain and pay the additional cost for a line just to
make telephone calls.
With many Internet
Voice plans you can talk for as long as you want with any
person in the world (the requirement is that the other person has an
Internet connection). You can also talk with many people at the same
time without any additional cost.
Some disadvantages of Internet Voice?
If you're considering replacing your
traditional telephone service with Internet Voice, there are some
Can I use my
Computer While I talk on the Phone?
Internet Voice services don't work during power outages and the
service provider may not offer backup power;
may be difficult for some Internet Voice services to seamlessly
connect with the 911 dispatch center or identify the location of
Internet Voice 911 callers; or
may or may not offer white page listings.
Can I Take My Phone Adapter with me When I
You may be able to use your VoIP service wherever you travel as long
as you have a high speed Internet connection available. In that case
it would work the same as from your home or business.
Does my Computer Have to be Turned on?
Not if you are making calls with a phone and adaptor or special VoIP
phone, but your broadband Internet connection needs to be active.
You can also use your computer while talking on the phone.
How Do I Know If I have a VoIP phone Call?
It will ring like any other call.
Does the FCC Regulate VoIP?
The Federal Communications Commission (FCC) has worked to create an
environment promoting competition and innovation to benefit
consumers. Historically, the FCC has not regulated the Internet or
the services provided over it. On February 12, 2004, the FCC found
that an entirely Internet-based VoIP service was an unregulated
information service. On the same day, the FCC began a broader
proceeding to examine what its' role should be in this new
environment of increased consumer choice and what it can best do to
meet its role of safeguarding the public interest.
The FCC has
organized an FCC Internet Policy Working Group to identify, evaluate
and address policy issues that will arise as telecommunications
services move to Internet-based platforms. For more information on
the Working Group, please visit www.fcc.gov/ipwg
of these considerations may change with new developments in internet
technology. You should always check with the VoIP service
provider you choose to confirm any advantages and limitations to
information about Internet Voice/VoIP see our factsheet. (pdf file)
of how the FAP is applied
Edition Service Plans
A.M. - 5:00 P.M. Eastern Standard Time
Tehese plans are not available in Canada but serve as an
example of how the FAP is applied
What Is Voice Over Internet Protocol?
VoIP is the process of sending sound or voice
over the internet. In a typical call using the current technology,
the voice starts as an analog signal. When the sound reaches the
transmitter in the phone, the vibrations are turned into electrical
impulses. The impulses are transmitted over a pair of wires to the
central office switch. The switch processes the electrical impulses
into digital information. This process is known as Analog to Digital
or Digital to Analog (A to D / D to A). This digital signal is
transmitted to a distant switch over a connection called a trunk
circuit. The main function of a telephone switch is to connect the
callers phone to the called party phone and convert analog signals
to digital information. The network of switches used every day in
the United States is known as the Public Switched Telephone Network
There are two sides to a switch, first is the
line side connection which is a two-wire circuit that connects the phone to the switch. This connection is
normally an analog link between the switch and the central office
(the name of the building where the switch is located). Second is
the trunk side of the switch. This connection is normally four-wire in nature and in most cases a digital link. The four-wire circuit is
a full duplex circuit where there is a dedicated transmission path
in both directions. Switches have many dedicated trunk groups that
connect the PSTN together in a spider web fashion.
VoIP is the next generation of telephone
technology. Major portions of the network are being replaced. The
traditional switch has been replaced with a device known as a
Gateway Controller. The GC provides an A to D function as well as
placing voice packets into the IP network for delivery to a distant
GC. Unlike the PSTN where switches use dedicated trunks, the VoIP
network uses a shotgun approach to deliver packets to the far end.
The theory is much the same in the VoIP and
traditional PSTN. The difference is in the method used to establish
a call. The PSTN uses multiple switches to connect a caller in
Chicago to someone in LA. In this example, let's say there are five
switches in the path between Chicago and LA. Each switch in the path
uses trunks that are dedicated between each switch. Switch one has
trunks connecting to switch two and switch two is connected to
switch three with dedicated trunks and so on and so on. The PSTN
uses phone numbers as the routing key to determine the next step in
the switching sequence. As a call arrives at the next switch in the
path, that switch queries its database to determine the trunk group
to use for routing the call to the distant end. A call making its
way across the nation hops from switch to switch in what appears to
be a helter-skelter fashion. The important factor in this scenario
is that for each switch pair involved there is a dedicated trunk
circuit locked up for the duration of the call. If there are two
calls between two switches then there are two trunks in use for the
length of each call.
In the VoIP network there are still switches in
the network, however; the switches are packet switches moving small
packets of data from point to point. The trunks have been replaced
with data links that are used to deliver packets where circuit
dedication is not required. Gateway Controllers break the voice into
small packets of information much the same as a switch in the PSTN.
The GC also starts the routing function by routing packets to a
distant IP address rather than routing on a phone number. The call
setup information, as well as the voice packets, hop through the IP
network in a ping-pong fashion much like the PSTN without dedicating
a circuit per call. Packets containing voice information are mixed
with data packets containing a web page or an e-mail in route to the
IP address assigned.
One thing that begins to come clear in the VoIP
network is the cost of call delivery. In the PSTN each call requires
a dedicated circuit and is not available for any other use during a
call. The VoIP network uses circuits in small bits at a time, that
is a phone call shares available circuits with anything else that
needs to be transmitted without the costly locked up circuits.
If you've never heard of VoIP, get ready
to change the way you think about long-distance phone calls. VoIP,
or Voice over Internet Protocol, is a method for taking analog
audio signals, like the kind you hear when you talk on the
phone, and turning them into digital
data that can be transmitted over the Internet.
How is this useful? VoIP can turn a standard Internet connection
into a way to place free phone calls. The practical upshot of
this is that by using some of the free VoIP software that is
available to make Internet phone calls, you are bypassing the phone
company (and its charges) entirely.
This person is using a computer to talk
to a friend in another state.
VoIP is a revolutionary technology that has the potential to
completely rework the world's phone systems. VoIP providers like Vonage
have already been around for a little while and are growing
steadily. Major carriers like AT&T
are already setting up VoIP calling plans in several markets around
the United States, and the FCC is looking seriously at the potential
ramifications of VoIP service.
Above all else, VoIP is basically a clever "reinvention of
the wheel." In this article, HowStuffWorks will show you the
principles behind VoIP, its applications and the potential of this
emerging technology, which will more than likely one day replace the traditional
phone system entirely.
The interesting thing about VoIP is that there is not just one way
to place a call. There are three different "flavors" of
VoIP service in common use today:
Try it Yourself
- ATA - The simplest and most common way is through the
use of a device called an ATA (analog telephone adaptor). The
ATA allows you to connect a standard phone to your computer or
your Internet connection for use with VoIP. The ATA is an
analog-to-digital converter. It takes the analog signal from
your traditional phone and converts it into digital data for
transmission over the Internet. Providers like Vonage and
AT&T CallVantage are bundling ATAs free with their service.
You simply crack the ATA out of the box, plug the cable from
your phone that would normally go in the wall socket into the
ATA, and you're ready to make VoIP calls. Some ATAs may ship
with additional software that is loaded onto the host computer
to configure it; but in any case, it is a very straightforward
- IP Phones - These specialized phones look just like
normal phones with a handset, cradle and buttons. But instead of
having the standard RJ-11 phone connectors, IP phones have an
RJ-45 Ethernet connector. IP phones connect directly to your router and have all the hardware and software necessary right onboard
to handle the IP call. Soon, Wi-Fi IP phones will be available, allowing subscribing callers to make VoIP calls from any Wi-Fi hot spot.
- Computer-to-computer - This is certainly the easiest way to use VoIP. You don't even have to pay for long-distance
calls. There are several companies offering free or very
low-cost software that you can use for this type of VoIP. All
you need is the software, a microphone, speakers,
a sound card and an Internet connection, preferably a fast one like
you would get through a cable or DSL modem. Except for your normal monthly ISP fee, there is
usually no charge for computer-to-computer calls, no matter the
If you're interested in trying VoIP, then you should check out some of the free VoIP software available on the Net. You should be able to download and set it up in about three to five minutes. Get a friend to download the software, too, and you can start tinkering with VoIP to get a feel for how it works. One place to look is SKYPE.
But chances are good you are already making VoIP calls any time you place a long-distance call. Phone companies use VoIP to streamline their networks. By routing thousands of phone calls through a circuit switch and into an IP gateway, they can seriously reduce the bandwidth they're using for the long haul. Once the call is received by a gateway on the other side of the call, it is decompressed, reassembled and routed to a local circuit switch.
Although it will take some time, you can be sure that eventually
all of the current circuit-switched networks will be replaced with packet-switching
technology (more on packet switching and circuit switching
later). IP telephony just makes sense, in terms of both economics
and infrastructure requirements. More and more businesses are
installing VoIP systems, and the technology will continue to grow in
popularity as it makes its way into our homes.
The Forrester Research Group predicts that nearly 5 million U.S. households
will have VoIP phone service by the end of 2006. Perhaps the biggest
draws to VoIP for the home users that are making the switch are price
With VoIP, you can make a call from anywhere you have broadband
connectivity. Since the IP phones or ATAs broadcast their info over
the Internet, they can be administered by the provider anywhere
there is a connection. So business travelers can take their phones
or ATAs with them on trips and always have access to their home
phone. Another alternative is the softphone. A softphone is
client software that loads the VoIP service onto your desktop or
laptop. The Vonage softphone has an interface on your screen that
looks like a traditional telephone. As long as you have a
headset/microphone, you can place calls from your laptop anywhere in
the broadband-connected world.
Most VoIP companies are offering minute-rate plans structured like cell
phone bills for as little as $15 per month. On the higher end,
some offer unlimited plans for $79. With the elimination of
unregulated charges and the suite of free features that are included
with these plans, it can be quite a savings.
Most VoIP companies provide the features that normal phone
companies charge extra for when they are added to your service plan.
There are also advanced call-filtering options available from some
carriers. These features use caller ID information to allow you make
a choice about how calls from a particular number are handled. You
- Call waiting
- Call transfer
- Repeat dial
- Return call
- Three-way calling
With many VoIP services, you can also check voicemail via the Web or
attach messages to an e-mail that is sent to your computer or
handheld. Not all VoIP services offer all of the features above.
Prices and services vary, so if you're interested, it's best to do a
- Forward the call to a particular number
- Send the call directly to voicemail
- Give the caller a busy signal
- Play a "not-in-service" message
- Send the caller to a funny rejection hotline
Now that we've looked at VoIP in a general sense, let's look more
closely at the components that make the system work. In order to
understand how VoIP really works and why it's an improvement over
the traditional phone system, it helps to first understand how a
traditional phone system works.
The Standard Phone System: Circuit
Existing phone systems are driven by a very reliable but somewhat inefficient
method for connecting calls called circuit switching.
Circuit switching is a very basic concept that has been used by telephone
networks for more than 100 years. When a call is made between
two parties, the connection is maintained for the duration of the
call. Because you are connecting two points in both directions, the
connection is called a circuit. This is the foundation of the
Public Switched Telephone Network (PSTN).
Here's how a typical telephone call works:
Let's say that you talk for 10 minutes. During this time, the
circuit is continuously open between the two phones. In the early
phone system, up until 1960 or so, every call had to have a
dedicated wire stretching from one end of the call to the other for
the duration of the call. So if you were in New York and you wanted
to call Los Angeles, the switches between New York and Los Angeles
would connect pieces of copper wire all the way across the United
States. You would use all those pieces of wire just for your call
for the full 10 minutes. You paid a lot for the call, because you
actually owned a 3,000-mile-long copper wire for 10 minutes.
- You pick up the receiver and listen for a dial tone. This lets
you know that you have a connection to the local office of your
- You dial the number of the party you wish to talk to.
- The call is routed through the switch at your local carrier to
the party you are calling.
- A connection is made between your telephone and the other
party's line using several interconnected switches along the
- The phone at the other end rings, and someone answers the
- The connection opens the circuit.
- You talk for a period of time and then hang up the receiver.
- When you hang up, the circuit is closed, freeing your line and
all the lines in between.
Telephone conversations over today's traditional phone network
are somewhat more efficient and they cost a lot less. Your voice is digitized,
and your voice along with thousands of others can be combined onto a
single fiber optic cable for much of the journey (there's still a dedicated
piece of copper wire going into your house, though). These calls are
transmitted at a fixed rate of 64 kilobits per second (Kbps) in each
direction, for a total transmission rate of 128 Kbps. Since there
are 8 kilobits (Kb) in a kilobyte (KB), this translates to a
transmission of 16 KB each second the circuit is open, and 960 KB
every minute it's open. So in a 10-minute conversation, the total
transmission is 9,600 KB, which is roughly equal to 10 megabytes
(check out How Bits and Bytes Work to learn about these conversions). If you
look at a typical phone conversation, much of this transmitted data
While you are talking, the other party is listening, which means
that only half of the connection is in use at any given time. Based
on that, we can surmise that we could cut the file in half, down to
about 4.7 MB, for efficiency. Plus, a significant amount of the time
in most conversations is dead air -- for seconds at a time, neither
party is talking. If we could remove these silent intervals, the
file would be even smaller. Then, instead of sending a continuous
stream of bytes (both silent and noisy), what if we sent just the
packets of noisy bytes when you created them? That is the basis of a
packet-switched phone network, the alternative to circuit switching.
The VoIP Phone System: Packet
Data networks do not use circuit switching. Your Internet connection
would be a lot slower if it maintained a constant connection to the Web
page you were viewing at any given time. Instead, data networks
simply send and retrieve data as you need it. And, instead of
routing the data over a dedicated line, the data packets flow
through a chaotic network along thousands of possible paths. This is
called packet switching.
While circuit switching keeps the connection open and constant,
packet switching opens a brief connection -- just long enough to
send a small chunk of data, called a packet,
from one system to another. It works like this:
- The sending computer chops data into small packets, with an
address on each one telling the network devices where to send
- Inside of each packet is a payload. The payload is a
piece of the e-mail, a music file or whatever type of file is
being transmitted inside the packet.
- The sending computer sends the packet to a nearby router
and forgets about it. The nearby router send the packet to
another router that is closer to the recipient computer. That
router sends the packet along to another, even closer router,
and so on.
- When the receiving computer finally gets the packets (which
may have all taken completely different paths to get there), it
uses instructions contained within the packets to reassemble the
data into its original state.
Packet switching is very efficient. It lets the network route the
packets along the least congested and cheapest lines. It also frees
up the two computers communicating with each other so that they can
accept information from other computers, as well.
VoIP technology uses the Internet's packet-switching capabilities to
provide phone service. VoIP has several advantages over circuit
switching. For example, packet switching allows several telephone
calls to occupy the amount of space occupied by only one in a
circuit-switched network. Using PSTN, that 10-minute phone call we
talked about earlier consumed 10 full minutes of transmission time
at a cost of 128 Kbps. With VoIP, that same call may have occupied
only 3.5 minutes of transmission time at a cost of 64 Kbps, leaving
another 64 Kbps free for that 3.5 minutes, plus an additional 128
Kbps for the remaining 6.5 minutes. Based on this simple estimate,
another three or four calls could easily fit into the space used by
a single call under the conventional system. And this example
doesn't even factor in the use of data
compression, which further reduces the size of each call.
Let's say that you and your friend both have service through a
VoIP provider. You both have your analog phones hooked up to the
service-provided ATAs. Let's take another look at that typical
telephone call, but this time using VoIP over a packet-switched
It will still be at least a decade before communications companies
can make the full switch over to VoIP. As with all emerging
technologies, there are certain hurdles that have to be overcome.
- You pick up the receiver, which sends a signal to the ATA.
- The ATA receives the signal and sends a dial tone. This lets
you know that you have a connection to the Internet.
- You dial the phone number of the party you wish to talk to.
The tones are converted by the ATA into digital data and
central call processor is a piece of hardware
running a specialized database/mapping program called a soft
switch. See the "Soft Switches" section to
- The phone number data is sent in the form of a request to your VoIP company's call processor. The call processor checks it to ensure that it is in a valid format.
- The call processor determines to whom to map the phone number.
In mapping, the phone number is translated to an IP
address (more on this later). The soft switch
connects the two devices on either end of the call. On the other
end, a signal is sent to your friend's ATA, telling it to ask
the connected phone to ring.
- Once your friend picks up the phone, a session is established
between your computer and your friend's computer. This means
that each system knows to expect packets of data from the other
system. In the middle, the normal Internet
infrastructure handles the call as if it were e-mail or a Web page. Each system must use the same protocol to
communicate. The systems implement two channels, one for each
direction, as part of the session.
- You talk for a period of time. During the conversation, your
system and your friend's system transmit packets back and forth
when there is data to be sent. The ATAs at each end translate
these packets as they are received and convert them to the
analog audio signal that you hear. Your ATA also keeps the
circuit open between itself and your analog phone while it
forwards packets to and from the IP host at the other end.
- You finish talking and hang up the receiver.
- When you hang up, the circuit is closed between your phone and
- The ATA sends a signal to the soft switch connecting the call,
terminating the session. Probably one of the most compelling
advantages of packet switching is that data networks already
understand the technology. By migrating to this technology,
telephone networks immediately gain the ability to communicate
the way computers do.
How it works
Voice over internet protocol (VoIP) is the latest technology that
uses the internet to transport you call as opposed to the
traditional public telephone switched network (PTSN). By using the
reliability of the internet and leveraging its low costs, calls can
be made anywhere in the world using VoIP technology . CDC allows you
to capitalise on this and process calls worldwide without the cost
of the ingress.
By taking advantage of H323, the international standard in VoIP,
CDC can offer a variety of services at greatly reduced costs
compared to traditional carriers. In addition to this, new
revolutionary features such are possible such as our Callshop
Solution and Telemarketing System.
Making a call from VoIP to a Regular Telephone
- Any regular analogue telephone can be connected to one of the
CDC ITG range of gateways. 2,4 or 8 telephone ports for up to 8
separate phone numbers. It is shipped pre-configured by CDC.
- Connecting a CDC ITG to your network is simple. All you need
is a broadband connection and an extra ethernet port on your hub
- Once the CDC ITG is connected to the internet it automticaly
finds the VoIP Gateway(s) and registers itself so that calls can
be made and received. This makes your phone number extremely
portable and will work anywhere in the world where there is an
internet connection -- a feature not available with traditional
- In this scenarios the CDC ITG is the originating gateway that
converts your voice signals to VoIP packets which will travel
over the internet.
- The terminating gateway then converts the VoIP packets back to
voice signals and connects to the PTSN (Public Switched
Telephone Network) to make the call to any telephone in the
Making a call from a Regular Telephone to VoIP
- The person calling you places a call using any regular
telephone and dials a regular number.
- The voice signals travel over the PTSN ( Public Switched
Telephone Network ) to an Enterprise VoIP Gateway.
- 1. The vocie signals are then converted to VoIP packets that
travel over the internet to your CDC ITG which is connected to
the internet regardless of where you are in the world. This
makes your phone number extremely portable and will work
anywhere in the world where there is an internet connection -- a
unique feature with this product.
- If you are in London, Spain or anywhere else in the world with
a broadband internet connection and the person calling you is in
the country that your soft switch is located calls can be made
without incurring any international charges.