Lines open

  • 14/02/1995

Lines open The modest telephone lines -- with their constantly evolving technology -- are going to stay as the backbone of the revolution in information technology.

Right now, fibre optics is making a big difference in telecommunications -- sophisticated lasers transform electrical representations of conversations, faxes, or data into light pulses, which speed through the fibre to their destinations, where they are converted back into electricity.

The most efficient fibre telephone lines today can carry 1-2 billion bits of information -- roughly an Encyclopaedia Britannica -- in a second. This is a 10,000-fold improvement over the conventional copper coaxial lines.

"Much of the current research on fibre-optics is aimed at driving the cost down," says Davis Hartman, the head of the optoelectronics research group at Motorola Inc in California, USA.

Another technology used for networking computers is through dedicated digital telephone lines frequently called leased lines. This network -- named as X.25 network -- eliminates the use of modems, but uses a device called a packet assembler-disassembler, or PAD, to break the data into little packets, each one with an address of its final destination. These little packets travel through the network, together with several other packets of data from other places. The PADs in different cities examine each packet's address and direct it to its destination.

Even as fibre optic cables are being laid, alternative ways of transmitting signals are being tried out: translating voices, data and video into a stream of digital pulses can now work for wireless networks as well -- a new route for the information highway to reach remote jungles which are inhospitable to cable-laying.

Satellite network is another technology which goes hand in hand with the information highway. The concept of satellite networking of computers involves a geostationary satellite and what are known as "very small aperture terminals", or VSATs, which are earth stations with a small antenna of 2.5 metre diameter to transmit and receive signals.

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