Learning Articles - Articles On Education

Telex Machine

The modern Telex system with its 800,000 subscribers in more than 100 countries (1978) is the combination of carrier telegraphy and teletypewriter. By temporarily connecting lines and switching equipment, subscribers can communicate directly with one another by means of teleprinters.

Telex service is analogous to the public telephone service except that machine-printed messages replace speech. The printed record makes telex particularly usefull in the business world, which requires the authority and authenticity of written messages or documents.

This teletypewriter possesses a typewriter keyboard which produces electrical signals that are transmitted to a distant point where the counterpart teletypewriter signals that are transmitted to a distant point where the counterpart teletypewriter then poduces a printed copy from the electrical signals transmitted to it, and vice versa. Messages are sent in a unit code at 67 words per minute. Calls can be made automatically, semi-automatically, or manually, depending on how the machines are set and how the calls are made.

Source : Groiler Electric Publishing Inc. & The World Book Encyclopedia: 1993.

Borobudur

Just 42 kilometres northwest of Yogyakarta stands the serene 1,000 year old Borobudur - the largest Buddhist monument in the world.

Borobudur was built between 778 and 856 - 200 years before Notre Dame was built. Yet, about a century after it was completed, it was mysteriously abandoned. At that time, the neighbouring Mount Merapi erupted and covered Borobudur with its volcanic ash. The temple was buried it for almost a millennium before was rediscovered in 1814. It was later restored with the help of UNESCO.

Process Make Call with Telephones

What if you want to talk right now to a friend who lives far away? The answer is simple. You pick up your telephone and press some buttons. Next, you hear a ringing sound-one, two, three rings. Then you hear your friend's voice say, "Hello". Making a phone call seems so easy. But did you ever think about what makes it possible?

When you talk on the phone, your voice is changed into an electric signal that can travel through wires. A plastic disk in the mouthpiece vibrates when you speak. The vibration makes a pattern in an electric field between the plastic disk and a metal disk. The pattern is sent through wires as an electric signal. Just as a telephone can turn a voice into an electric signal, it can also change an electric signal back into a voice. When the signals pass through magnets in the earpiece, the magnets vibrate a disk that reproduces the speaker's voice.

When you make a local call, the call travels over wires from your house to the telephone company's routing station. From there, a computer automatically sends the call to the number you dialed. Did you know you can call someone on other side of the world? The call might even be sent into space! Satellites orbiting high above Earth connect calls between distant countries. Some international calls travel along cables under the sea. Cell phones work by sending a radio signal through the air to a cell tower. The tower sends the signal to the cell phone company, which relays it to another cell phone or through the telephone company to a wired phone.

Communication Satellites

Astronauts have journeyed off the planet earth and out into space. Ventures into space have led to the latest tool in long-distance communication-the communications satellite. The satellite is equipped with radio receivers and transmitters. Rockets boost it into orbit, and the force of gravity keeps it from flying off into space. The communications satellite is the earth's captive, circling the planet in space. The satellite acts as a television relay station. Engineers on the earth bounce television signals off it at an single, and the signals come down at a different angle to receivers on another continent. Television signals are blocked by mountains, by the earth's curvature, or sometimes by buildings. Therefore, they have to be relayed from one transmitter to another in order to travel long distances.

In 1962, the first important United States Communications Satellite, Telstar I, was place in orbit. Television engineers in Europe bounced a picture off Telstar, and viewers in the United States saw it. For the first time, people sat at home in New York and watched something happening in London or Paris at the moment it took place.

In 1965, the United States launched Early Bird, the first commercial communications satellite and Rusia launched Molniya 1. Today people in many parts of the world watch live television from other continents.

The United States also launched Palapa, the communications satellite, for Indonesia. The Indonesian government bought this satellite. The existence of the Palapa Satellites has helped the development of communications in Indonesia. It is great importance for the people in Indonesia because Indonesia consist of thousands of islands.