What is a Pstn or a Public Switched Phone Telephone Network?
PSTN stands for public switched telephone network. It is the network of the public circuit-switched telephone networks around the world, just as the internet is the network of the various IP-based packet-switched networks. At first, PSTN was only a fixed-line analogy telephone system network, however, these days, it is almost exclusively digital and includes mobile phones as well as land lines.
The technical standards developed by the ITU-T are what generally govern the PSTN, as it uses E.163/E.164 addresses – that is, regular telephone numbers – in order to set its addresses.
At first, telephones didn’t have any network at all, but were in private use, paired up in their wiring. When users wished to speak to other people, they had as many phones as were necessary in order to communicate. If the person wished to speak to someone else, they whistled into a transmitter until the other person heard it and picked up
Later, a bell was added in order to signal an incoming call. Soon, a switch-hook was also added so that the exchange principle in telegraph networks could be employed. Each user’s home phone was hooked up to a local telephone exchange, and each of those telephone exchanges were then hooked up to trunks. These networks were all connected in a hierarchical layout until finally neighborhoods, cities, countries, and the world was all hooked up together. Thus, the PSTN was born.
The exchange system changed when automation entered into the picture through pulse dialing. This made exchanges much more sophisticated and required fewer human participants to connect a call. Later, multi-frequency dialing – which brought about the SS7 (signaling protocol) network – became the standard connection for the majority of exchanges by the end of last century.
Though the phone network was created using voice connections that were analog, and used manual switchboards, the automated telephone exchanges replaced those switchboards, and digital switch technologies were also introduced. Today, switches almost always use digital circuits among exchanges, while two-wire analog circuits are still utilized for connecting the majority of telephones. In the PSTN, the basic digital circuit is a 64-kilobits-per-second channel.
How to get free phone calls
When people talk about free phone calls, what they are referring to is voice over internet protocol, or VOIP in telecom parlance. With VOIP, users make calls through broadband data lines (DSL, cable, or fiber) rather than traditional copper phone lines. In layman’s terms, it’s essentially a new way to make phone calls over the internet.
However, it must be stated up front that even through the internet, phone calls aren’t completely “free.” While you won’t get a phone bill or see individual charges on your account, you still must pay a monthly or annual fee to get service. The free aspect of your phone service is the fact that calls are generally unlimited and include long-distance. The service is, however, decidedly cheaper than traditional phone service.
Case in point, I recently happened to see a television commercial advertising a new product called, “MagicJack.” The advertisement explained how the small unit which plugs into your computer’s USB port on one end and your home telephone on the other end saves you hundreds in phone charges per month.
The technology is called voice over internet protocol, or VOIP in tech lingo. And with the advent of broadband, it has become more popular as a cheaper alternative to traditional telephone service.
But here’s what you need to know about VOIP. The new technology has two significant limitations: 1) temporary loss of service with a power outage; and 2) choppy sound when your computer is performing a memory-intensive task such as uploading a video to YouTube.
Skype & Vonage
Two popular providers for internet telephony are Skype and Vonage. With Skype, both users must be Skype callers. One cannot go outside Skype to utilize the free phone call capability of the internet. Vonage is more similar to traditional phone service, yet is cheaper at $14.99 per month for their Basic 500 Minute Residential Plan which includes every feature you could want, plus free long-distance. And if you want unlimited minutes plus free international calling, choose Vonage’s Premium Unlimited Residential Plan at $24.99 per month.
The Money-Saving MagicJack
MagicJack has emerged as a major contender in the battle for the top VOIP telephone service provider. With an initial cost of only $39.95, MagicJack will provide you with unlimited local and long distance calling plus many other features for only $19.95 per year (you heard right, per year). So intriguing was the advertising that I had to check it out for myself.
The MagicJack
Network Certifications
This article provides the basic overview of the computer networking certifications such as Network+, MCSE, CCNA, CCNP and others. These certifications are important for the people who want to advance their careers in the IT especially in computer networking field. Certified people are always given preferences in jobs in all over the world.
Network+
Network + by Comptia is designed for the IT professionals who have more than nine months experience in network administration. The code for the Network+ certification is N10-003 and it was first introduce in 1997 by Comptia. Network+ is an entry level exam and it provides the base for the advance certifications such as MCSE, CCNA, CCNP and others. Network+ is designed specifically for the Network administrators and like the other certifications of Comptia, Network+ certification will not expired once it is achieved.
Security+
Security+ certification by Comptia is designed for the IT professionals who have more than 2 years experience in the field of network administration, system administration and network securities. The code for this certification is SY0101 and it was started by Comptia in 2002. The common topic that are covered in this certifications are network, security infrastructure, cryptography, authentication, access control, internal and external network attacks and the dealing with the company’s security.
MCSE
Microsoft Certified Systems Engineer is a well renowned network certification that is designed by Microsoft. MCSE is based on the Windows NT and Windows 2000 platforms and the Windows 2003 Server has been merged in the MCSE certification. MCSE never retires but the new versions are released by the Microsoft after sometime so the candidate has to be upgrading himself after some time. The ideal job description roles for the MCSE certified people are Systems engineer, Network Engineer, Network Consultant, and Systems Analysts jobs.
CCNA
Cisco Certified Network Associate is an introductory level exam by Cisco Systems. CCNA is well renowned exam that checks the candidate’s ability of network administration, LAN, WAN and routing. The basic topics that are covered in the CCNA are IP addressing, Subnetting, Routing IOS, Frame Relay, ISDN Lines, ATM, network devices, topologies and routers. CCNA paves the way for the most advanced certifications by Cisco Systems such as CCNP, CCIE and CCVP. The job role for the CCNA certified people is network administrator, systems administrator and network consultant.
CCNP
Cisco Certified Network Professional is an advanced level certification by Cisco Systems. It is a next level exam after CCNA. CCNP covers advanced networking topics that include WAN (Wide Area Network). CCNP certification is valid for three years. The topics that are covered in CCNP are advanced networking, LAN, WAN, Routing, IP addressing, converged networks, network security, VPN, quality of service and broadband technologies like VOIP, VOIP security, DSL and Cable net technology.
Google A Bit of History
The first question most people have is, “What the heck is a “Google?†It is a play on the word “googol,†which is the mathematical figure 1 followed by 100 zeros. Depending on the level of your love for math, this is either the greatest or lamest name for a search engine. Regardless, the clever kids at Google have turned it into a cultural standard.
The Beginning
Larry Page and Sergey Brin co-founded Google in January of 1996, then known as BackRub. The boys were in the early twenties and classic computer geeks. Sergey was born in Moscow, alum of the University of Michigan and visiting Stanford. Larry was assigned to be his guide. During this visit, they obviously hit it off or today nobody would give a hoot about linking strategies.
Although two men and the name “BackRub†may raise some questions, the name actually referred to a method for producing search engine rankings. Specifically, the BackRub search engine was designed to analyze the “back links†to a site. Although BackRub developed a following with those in the know, nothing much happened for a few years.
1998
As with most new businesses, the boys needed some serious cash. The brass at Yahoo was interested, but initially passed. Sun Microsystems, of all companies, provided an answer. Andy Bechtolsheim was one of the founders of Sun and, thus, had the necessary deep pockets. $100,000 later, the new search engine company was on the way to stardom.
A New Name
As legend has it, BackRub became Google for a rather humorous reason. Apparently, Bechtolsheim accidentally made the $100k check out to “Google, Inc.†You can make your own guess as to which one of the boys said, “Hey, I have an idea for a new name.†In September of 1998, Google opened a small office in Menlo Park, California. The rest, as they say, is history.
Today, Google is based in Mountain View, California. Google prefers email communication, but you can get a live voice by calling (650) 623-4000. If you really want to talk to them, refuse a charge from the company on the credit card you use for Adwords. They will contact you pretty quickly!
The company went public in 2004 [Symbol: GOOG] and has a stock value of around $380 per share. Larry and Sergey are sickeningly wealthy. One can assume that Andy Bechtolsheim is also doing all right.
The Future
In the last year or so, Google has certainly received its fair share of criticism. PageRank is almost useless in relation to ranking in search results. At the time of this writing, PageRank hasn’t worked for three days, which means a change, shuffle, dance or whatever you want to call it is coming.
On the competition front, things are a bit murky. It seems a week doesn’t go by without a patent lawsuit being filed against the company. MSN and Yahoo have started to raise the level of competition and more will be coming. Google’s reliance on AOL as a traffic source is also a bit troubling given the continual loss of market share by the company that nearly brought Time Warner down. Gmail is dogged by patent issues, not to mention questions about violations of the privacy of users. All and all, things are not as rosy compared to a few years ago, but they can hardly be called bad.
Your guess is as good as mine when it comes to predicting if Google will become just another search engine. Personally, I think it will, but not because of any of the above. Instead, the evolution of the Internet suggests there will be a next “big thing.†Who knows, maybe Google will get a Grub [Grub.org] in its Nutch [Nutch.org].
