Wireless technology makes it easy to get rid of the cables and take computing away from the desk. It's becoming the household norm, and while the technology is advancing quickly, there are some easy things you can do to improve your own wireless connectivity.
1. Position your Router
A wireless signal doesn't carry far, and any walls or large objects may cause interference. For this reason, a wireless router should be centrally located in your home to insure the best range possible. Place the router on a flat surface off the floor and away from obstructions. Additionally, there could be interference from a neighboring wireless signal. Make sure that you're using a unique wireless channel to limit interference.
2. Replace your Antenna
The antennas shipped with most routers are small antennas with omni-directional capabilities. These antennas broadcast a signal in all directions, which can be useful if you need wireless throughout your house, but the range is quite short. A directional antenna can improve range by focusing the signal in a specific way, allowing you to aim it where it's needed. These antennas are often called "high-gain" and the signal increase is measured in decibels (dB).
3. Get a Repeater
A wireless repeater is the easy and safe way to boost your signal. A repeater works very much like a router, but instead of creating a signal, it relays an existing signal. A repeater is easy to install and doesn't require any additional wires or connections. Multiple repeaters make it easy to create a home or business network with complete connectivity.
4. Make an Antenna Booster
It's possible to make a homemade reflector or antenna to improve your wireless signal. There are templates and building instructions on many Web sites across the internet to use materials as commonplace as foil and cardboard. Common designs are a parabolic satellite shape and a "coffee can" yagi antenna. Both can increase range and direct your signal, though homemade quality will vary.
5. Upgrade Firmware
Router manufacturers publish firmware updates regularly and upgrading your router can provide a performance boost and access to new features. Another option for the tech savvy is to install third-party firmware. There are a number of free, safe alternatives that may be compatible with your router. One project, DD-WRT, offers more robust features than many of the official firmware packages.
Using these tips, you should be able to squeeze every bit of connectivity out of your own home network. Check out HowStuffWorks' other articles on home networks to learn more.
Sources
· Northrup, Tony. "10 Tips for Improving Your Wireless Connection." Microsoft. http://www.microsoft.com/athome/moredone/wirelesstips.mspx
· http://howstuffworks.com/framed.htm?parent=improving-wireless-connection.htm&url=http://www.microsoft.com/athome/moredone/wirelesstips.mspx"Do-it-Yourself Wireless Antenna Update." http://binarywolf.com/249/
· http://howstuffworks.com/framed.htm?parent=improving-wireless-connection.htm&url=http://binarywolf.com/249/"8 Ways to Extend Wireless Network Range." http://www.wireless-thing.com/2006/02/25/8-ways-to-extend-wireless-network-range/
Taken from
http://communication.howstuffworks.com/improving-wireless-connection.htm
Monday, July 21, 2008
SMS
Just when we're finally used to seeing everybody constantly talking on their cell phones, it suddenly seems like no one is talking at all. Instead, they're typing away on tiny numerical pads, using their cell phones to send quick messages. SMS, or text messaging, has replaced talking on the phone for a new "thumb generation" of texters.
In this article, we'll find out how text messaging works, explore its uses and learn why it sometimes takes a while for your text message to get to its recipient.
SMS stands for short message service. Simply put, it is a method of communication that sends text between cell phones, or from a PC or handheld to a cell phone. The "short" part refers to the maximum size of the text messages: 160 characters (letters, numbers or symbols in the Latin alphabet). For other alphabets, such as Chinese, the maximum SMS size is 70 characters.
SMS Attack
Recently it has been suggested that SMS messages could be used to attack a cell phone system. The basic idea is very simple. If a large number of SMS messages were sent by computers to phones in a small geographical area (like a city), these messages would overwhelm the control channels and make it impossible for the cell phone system to set up calls. Now that cell phone providers know about the possibility of this threat, they can design systems to throttle messages coming from the SMSC onto the network.
But how do SMS messages actually get to your phone? If you have read How Cell Phones Work, you can actually see what is happening.
Even if you are not talking on your cell phone, your phone is constantly sending and receiving information. It is talking to its cell phone tower over a pathway called a control channel. The reason for this chatter is so that the cell phone system knows which cell your phone is in, and so that your phone can change cells as you move around. Every so often, your phone and the tower will exchange a packet of data that lets both of them know that everything is OK.
Your phone also uses the control channel for call setup. When someone tries to call you, the tower sends your phone a message over the control channel that tells your phone to play its ringtone. The tower also gives your phone a pair of voice channel frequencies to use for the call.
The control channel also provides the pathway for SMS messages. When a friend sends you an SMS message, the message flows through the SMSC, then to the tower, and the tower sends the message to your phone as a little packet of data on the control channel. In the same way, when you send a message, your phone sends it to the tower on the control channel and it goes from the tower to the SMSC and from there to its destination.
The actual data format for the message includes things like the length of the message, a time stamp, the destination phone number, the format, etc. For a complete byte-by-byte breakdown of the message format, see this page.
Why 160 Characters?
SMS was designed to deliver short bursts of data such as numerical pages. To avoid overloading the system with more than the standard forward-and-response operation, the inventors of SMS agreed on a 160-character maximum message size.
But the 160-character limit is not absolute. Length limitations may vary depending on the network, phone model and wireless carrier. Some phones don't allow you to keep typing once the 160-character limit is reached. You must send your message before continuing. However, some services will automatically break any message you send into chunks of 160 characters or less. So, you can type and send a long message, but it will be delivered as several messages.
Advantages of SMS
SMS has several advantages. It is more discreet than a phone conversation, making it the ideal form for communicating when you don't want to be overheard. It is often less time-consuming to send a text message than to make a phone call or send an e-mail. SMS doesn't require you to be at your computer like e-mail and instant messaging (IM) do -- although some phones are equipped for mobile e-mail and IM services. SMS is also a convenient way for deaf and hearing-impaired people to communicate.
SMS is a store-and-forward service, meaning that when you send a text message to a friend, the message does not go directly to your friend's cell phone. The advantage of this method is that your friend's cell phone doesn't have to be active or in range for you to send a message. The message is stored in the SMSC (for days if necessary) until your friend turns his cell phone on or moves into range, at which point the message is delivered. The message will remain stored on your friend's SIM card until he deletes it.
In addition to person-to-person messages, SMS can be used to send a message to a large number of people at a time, either from a list of contacts or to all the users within a particular area. This service is called broadcasting and is used by companies to contact groups of employees or by online services to distribute news and other information to subscribers.
In a 2004 University of Plymouth study on the psychology of SMS users, researchers found that mobile phone users were primarily either "texters" or "talkers" [ref]. Compared to the talkers, the texters sent nearly double the number of SMS messages and made less than half as many voice calls per month. The texters preferred SMS to voice calls for its convenience as well as for the ability to review a message before sending it.
Companies have come up with many uses for the service beyond just your typical person-to-person message. Because SMS doesn't overload the network as much as phone calls, it is frequently used by TV shows to let viewers vote on a poll topic or for a contestant. As a promotional tool, wireless carriers put up giant screens at concerts and other large-scale events to display text messages from people in the audience.
SMS History
SMS was created during the late 1980s to work with a digital technology called GSM (global system for mobile communications), which is the basis for most modern cell phones. The Norwegian engineers who invented it wanted a very simple messaging system that worked when users' mobile phones were turned off or out of signal range. Most sources agree that the first SMS message was sent in the UK in 1992.
As SMS was born in Europe, it's not surprising that it took a little longer to make its way to the United States. Even today, texting enjoys much greater popularity in Europe, though its stateside use is on the rise. A July 2005 study found that 37 percent of U.S. mobile phone owners had sent or received at least one text message in the previous month [ref].
You can use text messaging subscription services to get medication reminders sent to your phone, along with weather alerts, news headlines or even novels broken into 160-character "chapters." Internet search engines such as Yahoo! and Google have short messaging services that enable users to get information such as driving directions, movie showtimes or local business listings just by texting a query to the search engine's phone number. Social networking services such as Dodgeball use SMS to alert people who live in big cities when their friends or crushes are nearby. The possibilities for integrating SMS into your lifestyle seem endless.
SMS Criticism and Alternatives
Despite their popularity, short messaging services have received some criticism. Here are a few of the disadvantages of SMS:
· You have to pay for it. Most wireless plans charge for a certain number of text messages a month. Some only charge for user-originated messages, while others charge for incoming messages as well. If you exceed your message allowance, you may be charged 10 cents per message, and those little charges can add up.
· Speedy message delivery is not guaranteed. During periods of high traffic, it might be minutes or even hours before a message gets through.
· It's strictly for sending text messages. SMS does not support sending pictures, video or music files.
Alternatives to SMS Alternative messaging services allow for more elaborate types of messages. With EMS (Enhanced Messaging Service), you can send formatted text, sound effects, small pictures and icons. MMS (Multimedia Messaging Service) allows you to send animations, audio and video files in addition to text. If your mobile phone is EMS- or MMS-enabled, you can use these standards just as you would SMS. However, the cost per message will be higher.
Another alternative to using SMS is using an instant messaging program, such as AOL IM, on your cell phone. This can be in the form of software that's pre-installed on your phone, or you can use WAP (Wireless Application Protocol) to access the Internet and sign into your IM account. WAP is a protocol that gives you small, simplified versions of web pages that are easily navigable on your mobile phone or PDA (check out How WAP Works for more information). You can use it to send instant messages or actual e-mails from your phone.
A common complaint about SMS is its inefficient delivery structure -- when the message center is backed up, messages take longer to reach their destination. To make message delivery faster, networks are using more new next-generation technologies such as GPRS (General Packet Radio Service).
More Great Links
· SMS Tutorial
· 160 Characters
· Textually.org
· Dodgeball
Sources
· Barkhuus, Louise and Anna Vallgarda. "Saying it All in 160 Characters: Four Classes of SMS Conversations." IT University of Copenhagen, April 2004.
http://www1.itu.dk/graphics/ITU-library/Internet/Forskning/Technical_Reports/ITU-TR-2004-45.pdf
· Burns, Enid. "Teens, College Students Are Most Active Cell Phone Users." Click Z Network, August 29, 2005.
http://www.clickz.com/stats/sectors/wireless/article.php/3530886
· Clements, Tom. "SMS - Short But Sweet." http://developers.sun.com/techtopics/mobility/midp/articles/sms
· Coll, Steve. "In the Gulf, Dissidence Goes Digital." Washington Post, March 29, 2005. http://www.washingtonpost.com/ac2/wp-dyn/A8175-2005Mar28?language=printer
· Dybwad, Barb. "Morse Code Trumps SMS in Head-to-Head Speed Texting Combat." Engadget, May 6, 2005. http://engadget.com/entry/1234000463042528/
· Dybwad, Barb. "Only 25 Percent of Americans Using SMS." Engadget, March 21, 2005.
http://www.engadget.com/entry/1234000560036891/
· Gupta, Puneet. "Short Message Service: What, How and Where?" http://www.wirelessdevnet.com/channels/sms/features/sms.htm
· "Lecturer May Sue After SMS Sacking." Independent Online, September 13, 2005. http://www.iol.co.za/index.php?set_id=1&click_id=29&art_id=qw1126585085708B215
· "Linked By Their Phones, Chinese Take to the Streets." Textually.org, April 25, 2005. http://www.textually.org/textually/archives/2005/04/008069.htm
· Reid, Donna and Fraser Reid. "Insights into the Social and Psychological Effects of SMS Text Messaging."
http://www.160characters.org/documents/SocialEffectsofTextMessaging.pdf
· Trosby, Finn. "SMS, The Strange Duckling of GSM." http://www.telenor.com/telektronnik/volumes/pdf/3.2004/Page_187-194.pdf
Taken from
http://communication.howstuffworks.com/sms.htm
In this article, we'll find out how text messaging works, explore its uses and learn why it sometimes takes a while for your text message to get to its recipient.
SMS stands for short message service. Simply put, it is a method of communication that sends text between cell phones, or from a PC or handheld to a cell phone. The "short" part refers to the maximum size of the text messages: 160 characters (letters, numbers or symbols in the Latin alphabet). For other alphabets, such as Chinese, the maximum SMS size is 70 characters.
SMS Attack
Recently it has been suggested that SMS messages could be used to attack a cell phone system. The basic idea is very simple. If a large number of SMS messages were sent by computers to phones in a small geographical area (like a city), these messages would overwhelm the control channels and make it impossible for the cell phone system to set up calls. Now that cell phone providers know about the possibility of this threat, they can design systems to throttle messages coming from the SMSC onto the network.
But how do SMS messages actually get to your phone? If you have read How Cell Phones Work, you can actually see what is happening.
Even if you are not talking on your cell phone, your phone is constantly sending and receiving information. It is talking to its cell phone tower over a pathway called a control channel. The reason for this chatter is so that the cell phone system knows which cell your phone is in, and so that your phone can change cells as you move around. Every so often, your phone and the tower will exchange a packet of data that lets both of them know that everything is OK.
Your phone also uses the control channel for call setup. When someone tries to call you, the tower sends your phone a message over the control channel that tells your phone to play its ringtone. The tower also gives your phone a pair of voice channel frequencies to use for the call.
The control channel also provides the pathway for SMS messages. When a friend sends you an SMS message, the message flows through the SMSC, then to the tower, and the tower sends the message to your phone as a little packet of data on the control channel. In the same way, when you send a message, your phone sends it to the tower on the control channel and it goes from the tower to the SMSC and from there to its destination.
The actual data format for the message includes things like the length of the message, a time stamp, the destination phone number, the format, etc. For a complete byte-by-byte breakdown of the message format, see this page.
Why 160 Characters?
SMS was designed to deliver short bursts of data such as numerical pages. To avoid overloading the system with more than the standard forward-and-response operation, the inventors of SMS agreed on a 160-character maximum message size.
But the 160-character limit is not absolute. Length limitations may vary depending on the network, phone model and wireless carrier. Some phones don't allow you to keep typing once the 160-character limit is reached. You must send your message before continuing. However, some services will automatically break any message you send into chunks of 160 characters or less. So, you can type and send a long message, but it will be delivered as several messages.
Advantages of SMS
SMS has several advantages. It is more discreet than a phone conversation, making it the ideal form for communicating when you don't want to be overheard. It is often less time-consuming to send a text message than to make a phone call or send an e-mail. SMS doesn't require you to be at your computer like e-mail and instant messaging (IM) do -- although some phones are equipped for mobile e-mail and IM services. SMS is also a convenient way for deaf and hearing-impaired people to communicate.
SMS is a store-and-forward service, meaning that when you send a text message to a friend, the message does not go directly to your friend's cell phone. The advantage of this method is that your friend's cell phone doesn't have to be active or in range for you to send a message. The message is stored in the SMSC (for days if necessary) until your friend turns his cell phone on or moves into range, at which point the message is delivered. The message will remain stored on your friend's SIM card until he deletes it.
In addition to person-to-person messages, SMS can be used to send a message to a large number of people at a time, either from a list of contacts or to all the users within a particular area. This service is called broadcasting and is used by companies to contact groups of employees or by online services to distribute news and other information to subscribers.
In a 2004 University of Plymouth study on the psychology of SMS users, researchers found that mobile phone users were primarily either "texters" or "talkers" [ref]. Compared to the talkers, the texters sent nearly double the number of SMS messages and made less than half as many voice calls per month. The texters preferred SMS to voice calls for its convenience as well as for the ability to review a message before sending it.
Companies have come up with many uses for the service beyond just your typical person-to-person message. Because SMS doesn't overload the network as much as phone calls, it is frequently used by TV shows to let viewers vote on a poll topic or for a contestant. As a promotional tool, wireless carriers put up giant screens at concerts and other large-scale events to display text messages from people in the audience.
SMS History
SMS was created during the late 1980s to work with a digital technology called GSM (global system for mobile communications), which is the basis for most modern cell phones. The Norwegian engineers who invented it wanted a very simple messaging system that worked when users' mobile phones were turned off or out of signal range. Most sources agree that the first SMS message was sent in the UK in 1992.
As SMS was born in Europe, it's not surprising that it took a little longer to make its way to the United States. Even today, texting enjoys much greater popularity in Europe, though its stateside use is on the rise. A July 2005 study found that 37 percent of U.S. mobile phone owners had sent or received at least one text message in the previous month [ref].
You can use text messaging subscription services to get medication reminders sent to your phone, along with weather alerts, news headlines or even novels broken into 160-character "chapters." Internet search engines such as Yahoo! and Google have short messaging services that enable users to get information such as driving directions, movie showtimes or local business listings just by texting a query to the search engine's phone number. Social networking services such as Dodgeball use SMS to alert people who live in big cities when their friends or crushes are nearby. The possibilities for integrating SMS into your lifestyle seem endless.
SMS Criticism and Alternatives
Despite their popularity, short messaging services have received some criticism. Here are a few of the disadvantages of SMS:
· You have to pay for it. Most wireless plans charge for a certain number of text messages a month. Some only charge for user-originated messages, while others charge for incoming messages as well. If you exceed your message allowance, you may be charged 10 cents per message, and those little charges can add up.
· Speedy message delivery is not guaranteed. During periods of high traffic, it might be minutes or even hours before a message gets through.
· It's strictly for sending text messages. SMS does not support sending pictures, video or music files.
Alternatives to SMS Alternative messaging services allow for more elaborate types of messages. With EMS (Enhanced Messaging Service), you can send formatted text, sound effects, small pictures and icons. MMS (Multimedia Messaging Service) allows you to send animations, audio and video files in addition to text. If your mobile phone is EMS- or MMS-enabled, you can use these standards just as you would SMS. However, the cost per message will be higher.
Another alternative to using SMS is using an instant messaging program, such as AOL IM, on your cell phone. This can be in the form of software that's pre-installed on your phone, or you can use WAP (Wireless Application Protocol) to access the Internet and sign into your IM account. WAP is a protocol that gives you small, simplified versions of web pages that are easily navigable on your mobile phone or PDA (check out How WAP Works for more information). You can use it to send instant messages or actual e-mails from your phone.
A common complaint about SMS is its inefficient delivery structure -- when the message center is backed up, messages take longer to reach their destination. To make message delivery faster, networks are using more new next-generation technologies such as GPRS (General Packet Radio Service).
More Great Links
· SMS Tutorial
· 160 Characters
· Textually.org
· Dodgeball
Sources
· Barkhuus, Louise and Anna Vallgarda. "Saying it All in 160 Characters: Four Classes of SMS Conversations." IT University of Copenhagen, April 2004.
http://www1.itu.dk/graphics/ITU-library/Internet/Forskning/Technical_Reports/ITU-TR-2004-45.pdf
· Burns, Enid. "Teens, College Students Are Most Active Cell Phone Users." Click Z Network, August 29, 2005.
http://www.clickz.com/stats/sectors/wireless/article.php/3530886
· Clements, Tom. "SMS - Short But Sweet." http://developers.sun.com/techtopics/mobility/midp/articles/sms
· Coll, Steve. "In the Gulf, Dissidence Goes Digital." Washington Post, March 29, 2005. http://www.washingtonpost.com/ac2/wp-dyn/A8175-2005Mar28?language=printer
· Dybwad, Barb. "Morse Code Trumps SMS in Head-to-Head Speed Texting Combat." Engadget, May 6, 2005. http://engadget.com/entry/1234000463042528/
· Dybwad, Barb. "Only 25 Percent of Americans Using SMS." Engadget, March 21, 2005.
http://www.engadget.com/entry/1234000560036891/
· Gupta, Puneet. "Short Message Service: What, How and Where?" http://www.wirelessdevnet.com/channels/sms/features/sms.htm
· "Lecturer May Sue After SMS Sacking." Independent Online, September 13, 2005. http://www.iol.co.za/index.php?set_id=1&click_id=29&art_id=qw1126585085708B215
· "Linked By Their Phones, Chinese Take to the Streets." Textually.org, April 25, 2005. http://www.textually.org/textually/archives/2005/04/008069.htm
· Reid, Donna and Fraser Reid. "Insights into the Social and Psychological Effects of SMS Text Messaging."
http://www.160characters.org/documents/SocialEffectsofTextMessaging.pdf
· Trosby, Finn. "SMS, The Strange Duckling of GSM." http://www.telenor.com/telektronnik/volumes/pdf/3.2004/Page_187-194.pdf
Taken from
http://communication.howstuffworks.com/sms.htm
Telephone Country Codes
In 1980, Americans spent 2 billion minutes making international phone calls. By 2004, that figure jumped to 64 billion minutes [source: Federal Communications Commission]. Why the huge increase?
Country-specific calling codes let callers make international calls such as this one made by President George W. Bush to Chinese President Hu Jintao.
International calls are cheaper than they were in 1980. That makes it easier for foreign-born citizens to call the family back home. An increase in international business and travel is also responsible. The most popular international call markets from the United States are Canada, Mexico, the United Kingdom, Germany and India. These countries account for 38 percent of all international calls [source: Federal Communications Commission].
The very first transatlantic telephone cable went operational in 1956. It could only handle 36 calls at a time and cost $12 for the first three minutes (the equivalent of $92 in 2007). That's better than the very first transatlantic calls made via radio signals in 1927. Those cost $75 for the first three minutes ($872 in today's money!) [source: AT&T and The Inflation Calculator].
It's not easy to construct and maintain a worldwide telephone network. Keeping up with the increasing demand for international phone calls has required the cooperation and collaborative efforts of governments and private telecommunications companies around the globe.
Organizations like the International Telecommunication Union (a United Nations agency) help set the international numbering standards and technology protocols that safely route calls across oceans and continents.
The Public Switched Telephone Network
The Public Switched Telephone Network (PSTN), also known as Plain Old Telephone Service (POTS), is the wired phone system over which landline telephone calls are made. The PSTN relies on circuit switching. To connect one phone to another, the phone call is routed through numerous switches operating on a local, regional, national or international level. The connection established between the two phones is called a circuit.
Tourists often rely on pay phones to make calls when traveling, and calling codes allow those calls to be made.
In the early days, phone calls traveled as analog signals across copper wire. Every phone call needed its own dedicated copper wire connecting the two phones. That's why you needed operators' assistance in making calls. The operators sat at a switchboard, literally connecting one piece of copper wire to another so that the call could travel across town or across the country. Long-distance calls were comparatively expensive, because you were renting the use of a very long piece of copper wire every time you made a call.
Beginning in the 1960s, voice calls began to be digitized and manual switching was replaced by automated electronic switching [source: WirelessCenter]. Digital voice signals can share the same wire with many other phone calls. The advent of fiber-optic cables now allows thousand of calls to share the same line. But fiber-optic and other high-bandwidth cables haven't changed the basic nature of circuit switching, which still requires a connection -- or circuit -- to remain open for the length of the phone call.
Routing calls requires multiple switching offices. The phone number itself is a coded map for routing the call. In the United States, for example, we have 10-digit phone numbers.
· The first three digits are the area code or national destination code (NDC), which helps route the call to the right regional switching station.
· The next three digits are the exchange, which represents the smallest amount of circuits that can be bundled on the same switch. In other words, when you make a call to another user in your same exchange -- maybe a neighbor around the corner -- the call doesn't have to be routed onto another switch.
· The last four digits of the phone number represent the subscriber number, which is tied to your specific address and phone lines.
Within a company or larger organization, each employee or department might have its own extension. Extensions from the main phone number are routed through something called a private branch exchange (PBX) that operates on the premises.
To make an international call requires further instructions. The call needs to be routed through your long-distance phone carrier to another country's long-distance phone carrier. To signal such a switch, you have to dial two separate numbers, your country's exit code (or international access code) and the corresponding country code of the place you're calling.
Almost all exit codes are either 00 or 011, although there are a few exceptions like Cuba (119) and Nigeria (009). Country codes are one- to three-digit prefixes that are assigned to specific countries or groups of countries. For example, the country code for the United States is 1, but the United States shares that country code with Canada and several smaller island nations like Jamaica, Puerto Rico and Guam. The country code for Mexico is 52 and Saudi Arabia is 966. Here's a full list of exit and country codes.
The Telecommunication Standardization Sector
The Telecommunication Standardization Sector is part of the International Telecommunication Union (ITU), an agency of the United Nations. The ITU, based in Geneva, Switzerland, works with 191 member countries to develop and implement global communications technology.
The specific responsibility of the Telecommunication Standardization Sector (ITU-T) is to research and recommend standards and protocols relating to voice and data transmissions over landline and mobile networks. This includes everything from streaming video on cell phones to Voice over IP (VoIP) to SMS to international call rates.
As business professionals travel more, they rely on calling codes to make international calls so they can stay in touch with home and office.
When it was established in 1925, the ITU-T was called the Comité Consultatif International Téléphonique et Télégraphique (CCITT). The CCITT was responsible for breakthrough work in standardizing fax data transmissions, modems, data compression, packet-switching and e-mail. The CCITT became the ITU-T in 1993 as part of a new strategic plan to respond quicker to the ever-changing technological landscape [source: International Telecommunication Union].
The ITU-T is best known for its recommendations. As their name implies, recommendations aren't laws or regulated standards, but merely suggestions for the best way to make telecommunications technology and networks run smoothly. Recommendations are established by 13 study groups within the ITU-T. Each study group is comprised of international managers and rapporteurs (appointees) from the public and private sector. A typical study group might include a CTO from Israel, a researcher from Germany and an American policymaker from the Federal Communications Commission.
Study groups are assigned a handful of questions, which they research over the course of two to four years before publishing their recommendations. Questions resemble topics. Current examples of questions include:
· Optical fiber cable network maintenance
· Traffic engineering for mobile communications
· Voice and video IP applications over cable television networks
· Real-time audio, video and data communication over packet-switched networks
The ITU-T also organizes focus groups, which are smaller research units within a study group working on a specific problem or question. Recommendations are published online and are free to the public as well as private industry and government agencies.
The Numbering Plan E.164
The E.164 recommendation, also called the "international public telecommunications numbering plan," was first approved and published by the ITU-T in May 1997. The E.164 recommendation establishes a standard framework for every country to create its own international phone numbers.
An international E.164 number is designed to include all of the necessary information to successfully route a call to an individual subscriber on a nation's public telephone network. Here's how the E.164 numbering plan works:
· A telephone number can have a maximum of 15 digits
· The first part of the telephone number is the country code (one to three digits)
· The second part is the national destination code (NDC)
· The last part is the subscriber number (SN)
· The NDC and SN together are collectively called the national (significant) number
The combined length of the national (significant) number can't exceed (15-n), where n is the amount of digits in the country code. This allows each country to decide how many digits should be in the national destination code and the subscriber number. A country with a relatively small population and few major cities, for example, might choose to have fewer digits in their phone numbers. And for larger countries, the possibilities are nearly endless. A 15-digit number allows for 100 trillion different permutations, enough for each person on earth to have 10,000 phone numbers [source: SearchNetworking].
International telephone numbers include a specific number that identifies the country, region and specific users so callers can dial directly home.
The United States subscribes to a system called the North American Numbering Plan. The North American Numbering Plan was actually created by AT&T in 1947, but it conforms with the framework recommended by the E.164 [source: North American Numbering Plan]. The North American Numbering Plan has a one-digit country code, a three-digit national destination code (called a Numbering Plan Area code, or just area code) followed by a seven-digit subscriber number.
Not all nations have a standard amount of digits for every location in the country. In Mexico, for example, the three largest cities -- Mexico City, Guadalajara and Monterrey -- have eight-digit subscriber numbers while all other locations have seven-digit numbers. The important thing is that all Mexican phone numbers adhere to the standards set forth by the E.164 recommendation.
The E.164 recommendation is currently being expanded into a much broader protocol called ENUM, short for TElephone NUmber Mapping. Using the international E.164 number as a model, ENUM will assign a specific Uniform Resource Identifier (URI) to each and every networked device, including analog telephones and fax machines, mobile phones, computers and PDAs. With this new URI, all these devices will be able to contact each other directly using a single network address/phone number. As of this writing, a final ENUM recommendation hasn't been published.
More Great Links
· North American Numbering Plan Administration
· Telecommunication Standardization Sector
Taken from
http://communication.howstuffworks.com/telephone-country-codes.htm
Country-specific calling codes let callers make international calls such as this one made by President George W. Bush to Chinese President Hu Jintao.
International calls are cheaper than they were in 1980. That makes it easier for foreign-born citizens to call the family back home. An increase in international business and travel is also responsible. The most popular international call markets from the United States are Canada, Mexico, the United Kingdom, Germany and India. These countries account for 38 percent of all international calls [source: Federal Communications Commission].
The very first transatlantic telephone cable went operational in 1956. It could only handle 36 calls at a time and cost $12 for the first three minutes (the equivalent of $92 in 2007). That's better than the very first transatlantic calls made via radio signals in 1927. Those cost $75 for the first three minutes ($872 in today's money!) [source: AT&T and The Inflation Calculator].
It's not easy to construct and maintain a worldwide telephone network. Keeping up with the increasing demand for international phone calls has required the cooperation and collaborative efforts of governments and private telecommunications companies around the globe.
Organizations like the International Telecommunication Union (a United Nations agency) help set the international numbering standards and technology protocols that safely route calls across oceans and continents.
The Public Switched Telephone Network
The Public Switched Telephone Network (PSTN), also known as Plain Old Telephone Service (POTS), is the wired phone system over which landline telephone calls are made. The PSTN relies on circuit switching. To connect one phone to another, the phone call is routed through numerous switches operating on a local, regional, national or international level. The connection established between the two phones is called a circuit.
Tourists often rely on pay phones to make calls when traveling, and calling codes allow those calls to be made.
In the early days, phone calls traveled as analog signals across copper wire. Every phone call needed its own dedicated copper wire connecting the two phones. That's why you needed operators' assistance in making calls. The operators sat at a switchboard, literally connecting one piece of copper wire to another so that the call could travel across town or across the country. Long-distance calls were comparatively expensive, because you were renting the use of a very long piece of copper wire every time you made a call.
Beginning in the 1960s, voice calls began to be digitized and manual switching was replaced by automated electronic switching [source: WirelessCenter]. Digital voice signals can share the same wire with many other phone calls. The advent of fiber-optic cables now allows thousand of calls to share the same line. But fiber-optic and other high-bandwidth cables haven't changed the basic nature of circuit switching, which still requires a connection -- or circuit -- to remain open for the length of the phone call.
Routing calls requires multiple switching offices. The phone number itself is a coded map for routing the call. In the United States, for example, we have 10-digit phone numbers.
· The first three digits are the area code or national destination code (NDC), which helps route the call to the right regional switching station.
· The next three digits are the exchange, which represents the smallest amount of circuits that can be bundled on the same switch. In other words, when you make a call to another user in your same exchange -- maybe a neighbor around the corner -- the call doesn't have to be routed onto another switch.
· The last four digits of the phone number represent the subscriber number, which is tied to your specific address and phone lines.
Within a company or larger organization, each employee or department might have its own extension. Extensions from the main phone number are routed through something called a private branch exchange (PBX) that operates on the premises.
To make an international call requires further instructions. The call needs to be routed through your long-distance phone carrier to another country's long-distance phone carrier. To signal such a switch, you have to dial two separate numbers, your country's exit code (or international access code) and the corresponding country code of the place you're calling.
Almost all exit codes are either 00 or 011, although there are a few exceptions like Cuba (119) and Nigeria (009). Country codes are one- to three-digit prefixes that are assigned to specific countries or groups of countries. For example, the country code for the United States is 1, but the United States shares that country code with Canada and several smaller island nations like Jamaica, Puerto Rico and Guam. The country code for Mexico is 52 and Saudi Arabia is 966. Here's a full list of exit and country codes.
The Telecommunication Standardization Sector
The Telecommunication Standardization Sector is part of the International Telecommunication Union (ITU), an agency of the United Nations. The ITU, based in Geneva, Switzerland, works with 191 member countries to develop and implement global communications technology.
The specific responsibility of the Telecommunication Standardization Sector (ITU-T) is to research and recommend standards and protocols relating to voice and data transmissions over landline and mobile networks. This includes everything from streaming video on cell phones to Voice over IP (VoIP) to SMS to international call rates.
As business professionals travel more, they rely on calling codes to make international calls so they can stay in touch with home and office.
When it was established in 1925, the ITU-T was called the Comité Consultatif International Téléphonique et Télégraphique (CCITT). The CCITT was responsible for breakthrough work in standardizing fax data transmissions, modems, data compression, packet-switching and e-mail. The CCITT became the ITU-T in 1993 as part of a new strategic plan to respond quicker to the ever-changing technological landscape [source: International Telecommunication Union].
The ITU-T is best known for its recommendations. As their name implies, recommendations aren't laws or regulated standards, but merely suggestions for the best way to make telecommunications technology and networks run smoothly. Recommendations are established by 13 study groups within the ITU-T. Each study group is comprised of international managers and rapporteurs (appointees) from the public and private sector. A typical study group might include a CTO from Israel, a researcher from Germany and an American policymaker from the Federal Communications Commission.
Study groups are assigned a handful of questions, which they research over the course of two to four years before publishing their recommendations. Questions resemble topics. Current examples of questions include:
· Optical fiber cable network maintenance
· Traffic engineering for mobile communications
· Voice and video IP applications over cable television networks
· Real-time audio, video and data communication over packet-switched networks
The ITU-T also organizes focus groups, which are smaller research units within a study group working on a specific problem or question. Recommendations are published online and are free to the public as well as private industry and government agencies.
The Numbering Plan E.164
The E.164 recommendation, also called the "international public telecommunications numbering plan," was first approved and published by the ITU-T in May 1997. The E.164 recommendation establishes a standard framework for every country to create its own international phone numbers.
An international E.164 number is designed to include all of the necessary information to successfully route a call to an individual subscriber on a nation's public telephone network. Here's how the E.164 numbering plan works:
· A telephone number can have a maximum of 15 digits
· The first part of the telephone number is the country code (one to three digits)
· The second part is the national destination code (NDC)
· The last part is the subscriber number (SN)
· The NDC and SN together are collectively called the national (significant) number
The combined length of the national (significant) number can't exceed (15-n), where n is the amount of digits in the country code. This allows each country to decide how many digits should be in the national destination code and the subscriber number. A country with a relatively small population and few major cities, for example, might choose to have fewer digits in their phone numbers. And for larger countries, the possibilities are nearly endless. A 15-digit number allows for 100 trillion different permutations, enough for each person on earth to have 10,000 phone numbers [source: SearchNetworking].
International telephone numbers include a specific number that identifies the country, region and specific users so callers can dial directly home.
The United States subscribes to a system called the North American Numbering Plan. The North American Numbering Plan was actually created by AT&T in 1947, but it conforms with the framework recommended by the E.164 [source: North American Numbering Plan]. The North American Numbering Plan has a one-digit country code, a three-digit national destination code (called a Numbering Plan Area code, or just area code) followed by a seven-digit subscriber number.
Not all nations have a standard amount of digits for every location in the country. In Mexico, for example, the three largest cities -- Mexico City, Guadalajara and Monterrey -- have eight-digit subscriber numbers while all other locations have seven-digit numbers. The important thing is that all Mexican phone numbers adhere to the standards set forth by the E.164 recommendation.
The E.164 recommendation is currently being expanded into a much broader protocol called ENUM, short for TElephone NUmber Mapping. Using the international E.164 number as a model, ENUM will assign a specific Uniform Resource Identifier (URI) to each and every networked device, including analog telephones and fax machines, mobile phones, computers and PDAs. With this new URI, all these devices will be able to contact each other directly using a single network address/phone number. As of this writing, a final ENUM recommendation hasn't been published.
More Great Links
· North American Numbering Plan Administration
· Telecommunication Standardization Sector
Taken from
http://communication.howstuffworks.com/telephone-country-codes.htm
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