AddThis

Bookmark and Share
Custom Search



PLC Power line communication, also known as power line carrier, mains communication, power line telecom (PLT), or power line networking (PLN), is a system for carrying data on a conductor also used for electric power transmission. Broadband over Power Lines (BPL) uses PLC by sending and receiving radio signals over power lines.
Electrical power is transmitted over high voltage transmission lines, distributed over medium voltage, and used by the end users at lower voltages. Power line communications can be applied at each stage. Most PLC technologies limit themselves to one set of wires, but some can cross between two levels eg, both the distribution network and premises wiring.
All power line communications systems operate by impressing a modulated carrier signal on the wiring system. Different types of power line communications use different frequency bands, depending on the signal transmission characteristics of the power wiring used. Since the power wiring system was originally introduced for transmission of AC power, the power wire circuits have only a limited ability to carry higher frequencies. The propagation problem is a limiting factor for each type of power line communications.
Data rates over a power line communication system vary widely. Low-frequency (about 100-200 kHz) carriers impressed on high-voltage transmission lines may carry one or two analog voice circuits, or telemetry and control circuits with an equivalent data rate of a few hundred bits per second; although, these circuits may be many miles / kilometers long. Higher data rates generally imply shorter ranges; a local area network operating at millions of bits per second may only cover one floor of an office building, but eliminates installation of dedicated network cabling system.

Posted by Kami Saturday, May 31, 2008 0 comments


I want to tell you about
1- submarine communication,
2- amplifiers
3- repeaters
4- fiber optics
5-telecommunication network and fiber optic cables.


The cable protection committee was established in 1958 in London to protect the submarine cables.
This committee is funded by the member fiber optic cable operators and the main responsibilities of this committee to protect the submarine communication cable. Earlier telecom submarine cables were not using repeaters so there were great bandwidth problems. In 1980 fiber optical was developed it uses the optical amplifiers to transmit the signals at a very high speed. Submarine power cables are running for supplying the electrical power. Fishing, anchoring and shark fish bites can cause the damage to the cables and the damaged portion of the cable is brough Submarine communication cables are the fiber optical cables and are used for the cross Atlantic communications. Submarine cables are consisting of fiber optics and electrical conductive tube that is used to transfer the electrical signals between the repeaters. Repeaters are the network communication and telecom devices that are used to amplify the signals. Repeaters operate at the physical layer of the OSI layers model and work with the physical signals. Submarine fiber optical cables are less susceptible to failure and are very high transmission cables.

Submarine fiber optical cables are usually laid under the sea. A great research and planning is required to install the submarine fiber optic cables. Fiber optic cable is a light weight cable, 13 cm in diameter and consists of a bunch of glass fibers that are cable of transmitting the light. So the data is transferred at the speed of light through the fiber optic cables. Normally the submarine cables are not installed on the area where the fishing and ship activities are very common.

Because ship anchor and shipping vessels can be the problem for the submarine cables. Submarine telecommunication cable is a cable that is used for the telecommunication between the countries across the world. With the passage of time, the submarine cables have advancements and new technologies and communication devices are being used in the telecommunication. Submarine telecommunication cables with the high amplifier can transmit data and signals at more than 5 GB per seconds. Submarine cables were first used for the telegraphic transmission between the countries, then for telephone and then for data communication.

Today, fiber optic submarine cable is the backbone of the whole internet. In case of any damage to the submarine cables the whole communication system may be affected allot. The international t to the surface for repairing purposes. The installation and the repairing cost of the submarine cables is much high. These cables are laid in the seabed by the cable lying ships. These ships are owned and operated by the wireless and big telecommunication companies around the world. The optical fibers in the fiber optic are used as a sensor to measure heat, pressure and temperature.

Fibers are made up of transparent plastic and glass to pass the light at a very high speed. Earthquakes are also the cause of the damage for the communication cables and a major Tsunami earthquake in December 2004, caused big damages to the underlying telecom cables. Telecom cables have a large network across the world. Some of the major submarine cable companies of the world are Apollo, Pan American Crossing, Pacific Rim East, Japan-US, Columbus II, Columbus III, RJK, Eastern Caribbean fiber system and many other companies.

Posted by Kami Sunday, May 25, 2008 1 comments


Blackness Of The White.

The title of mine today article is very much looks like any title of a Holly Wood new release. Well, I fell it same too. But I am just going to tell you something valuable about the white fluorescent light emanating from a typical artificial light source.As we all know a few years back incandescent lamps with their yellowish light were much popular. And then revolution came in and compact fluorescent lamps (CFL) in common terms "Energy Savers Lamps" become substitute for those incandescent lamps.

The compact fluorescent lamps produce a very humble, polite, and white light which is suitable almost for everyone.But very few persons know the blackness behind this white light. I mean to say that the Cfls use a few amount of Mercury for its operation.Ttherefore users have to take much care about handling it. So do not break it.Because if the Mercury inhaled or absorbed through skin and mucous membrane then due to its neurotoxin effect it may harm the follwoings!

1. Kidneys
2. Brain (and may also cause for the followings)
3. Chest Pain
4. Cough
5. Impairment of Pulmonary Function

As we all know that the modern land fields have been made to buried the wastage produced by all of us. But the mercury which minor quantity uses in the Clfs do not tossed in to the land fields and remain dangerous for the soil , water, and the environment. So, particularly keep children away from wasted or out of order Clfs. And believe me I am not against the manufacturers or users but I fell it is my responsibility to share you the safety measures to handle the Clfs through this unique forum.

Thanks!

Posted by Kami Friday, May 23, 2008 0 comments

LCD













About Color Liquid Crystal Display (LCD)

The LCD that can show colors must have three subpixels with
1.red
2. green
3.blue color filters to create each color pixel.

Through the careful control and variation of the voltage applied, the intensity of each subpixel can range over 256 shades. Combining the subpixels produces a possible palette of 16.8 million colors (256 shades of red x 256 shades of green x 256 shades of blue). These color displays take an enormous number of transistors. For example, a typical laptop computer supports resolutions up to 1,024x768. If we multiply 1,024 columns by 768 rows by 3 subpixels, we get 2,359,296 transistors etched onto the glass! If there is a problem with any of these transistors, it make a "bad pixel" on the display. Most active matrix displays have a few bad pixels scattered across the screen.
LCD technology is constantly evolving. LCDs today employ several variations of liquid crystal technferroelectric liquid crystal (FLC) and surface stabilized ferroelectric liquid crystal (SSFLC).

Display size is limited by the quality-control problems faced by manufacturers. Simply put, to increase display size, manufacturers must add more pixels and transistors. As they increase the number of pixels and transistors, they also increase the chance of including a bad transistor in a display. Manufacturers of existing large LCDs often reject about 40 percent of the panels that come off the assembly line. The level of rejection directly affects LCD price since the sales of the good LCDs must cover the cost of manufacturing both the good and bad ones. Only advances in manufacturing can lead to affordable displays in bigger sizes.

Posted by Kami Sunday, May 18, 2008 0 comments

Subscribe here