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Techno
Page - By Harendra Alwis
What is DSL?
DSL is a very high-speed connection that uses the same wires as a regular telephone line. If you have an idea about how telephones work, then you know that a standard telephone installation consists of a pair of copper wires that the phone company installs in your home. The copper wires have lots of room for carrying more than your phone conversations. They are capable of handling a much greater bandwidth, or range of frequencies, than required for voice. DSL exploits this "extra capacity" to carry information on the wire without disturbing the line's ability to carry conversations. The entire plan is based on matching particular frequencies to specific tasks. To understand DSL, you first need to know a couple of things about a normal telephone line. Telephone professionals call them POTS, or "Plain Old Telephone Service". One of the ways that POTS makes the most of the telephone company's wires and equipment is by limiting the frequencies that the switches, telephones and other equipment will carry. Human voices, speaking in normal conversational tones, can be carried in a frequency range of 0 to 3,400 Hertz . The use of such a small portion of the wire's total bandwidth is practically ancient technology. Telephones have been in place, using a pair of copper wires to each home, for about a century. By limiting
the frequencies carried over the lines, the telephone system can
pack lots of wires into a very small space without worrying about
interference between lines. The news that Sri Lanka Telecom will be giving out ADSL connections in the near future has created a growing interest in ADSL technology and many seem to be eager to know what ADSL actually is. ADSL stands for Asymmetric Digital Subscriber Line. Precisely how much benefit you see will greatly depend on how far you are from the central office of the company providing the ADSL service. ADSL is a distance-sensitive technology: As the connection's length increases, the signal quality decreases and the connection speed goes down. The limit for ADSL service is 18,000 feet (5,460 metres), though for speed and quality of service reasons many ADSL providers place a lower limit on the distances for the service. At the extremes of the distance limits, ADSL customers may see speeds far below the promised maximums, while customers nearer the central office have faster connections and may see extremely high speeds in the future. ADSL technology can provide maximum downstream (Internet to customer) speeds of up to 8 megabits per second (Mbps) at a distance of about 6,000 feet (1,820 metres), and upstream speeds of up to 640 kilobits per second (Kbps). In practice, the best speeds widely offered today are 1.5 Mbps downstream, with upstream speeds varying between 64 and 640 Kbps. This is just the core information about ADSL. If you know more and wish to share it with other readers, please feel free to write in.
I'm certain that e-learning has already become a part of my life. This flexible virtual learning vehicle is well supported by comprehensive online learning tools. Students can access course materials conveniently through a Web browser. Receiving of lecture notes, assignments, student handouts, submission of assignments and many more is done via Internet. Online discussion threads are available for the students to post in their questions regarding a particular topic. The facilitators reply the questions in no time. Online chat sessions are conducted to enable students to have discussions with the lecturers. This brings out the aspect of a typical classroom even though it is not within one physical classroom. Students belonging to different nationalities from other parts of the world log in at the same time to discuss subject matters, which is really interesting. It also provides services like monitoring and feedback of students' progress and performance, private e-mail facilities as well as round-the-clock customer service. When I finish this online final year programme, I will receive the same qualification that a student who is studying at the University of Portsmouth (UK) would receive. Anyone, anywhere with a PC can follow the same training course, without leaving his or her desk. Besides, one could reap the obvious time and cost savings by not having to travel. E-learning can provide a more personal training experience as it allows for flexibility in content absorption and collaborative work via e-mail, chat, forums and virtual meetings. Individuals can train in their own time to become more marketable and improve their career prospects. There is little doubt there are many people who still believe that traditional classroom based training is the most effective way to learn, but many also acknowledge that it can be a time consuming and expensive option. The reality is that many businesses and individuals cannot afford to take time out to train or be trained, and this has contributed to the growth of self-study. This solution has the benefit of flexibility to fit into an individual's lifestyle, but can prove ineffective for those who find it difficult to maintain motivation and self-discipline. Hence, the option of e- learning, which combines the interaction of classroom based teaching with the flexibility of self-study, is becoming increasingly popular. I personally have really enjoyed e-learning and it has definitely improved my skills, thus making it a positive part of my life. I hope that in the future many students will earn degrees through e learning and serve our country. - Suhadhini
Perera Email:
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