Read the text and follow the instructions.

History and Regulation of the Telephone Industry.

" Mr. Watson, come here, I want you." With these historic words Alexander Graham Bell called to his assis­tant Thomas Augustus Watson over the so-called " tele­phone", and an industry was born.

The place: 5 Exeter Place, Boston, Massachusetts.

The time: evening, March 10, 1876.

As with all inventions, the road had not been smooth. For years, Graham Bell (as he liked to be called) had been experimenting with harmonic telegraph. It should be possible, he reasoned, to send six tones over the same wire at the same time and cause six reeds at­tached to the receiving end to be operated. Furthermore, if all worked well, varied combinations of these six pitches could reproduce human speech.

Simultaneously he was working on a scheme that utilized the varying resistance of a wire. A diaphragm, which would be vibrated by the human voice, was at­tached to a wire that was dipped into a mixture of acid and water. In theory, as the diaphragm moved down­ward, forcing more wire into the acid, the resistance of the wire would be decreased. As the diaphragm moved

necessary handshaking information - again, by, accumu­lating a packet of data, seizing a channel, and bursting the information out over that channel. Again, 100 per­cent efficient.

As mentioned earlier, the packet networks in the world (actually overlay networks to the PSTN) are being used extensively for data: only recently are we seeing them being used for voice. As systems are perfected, this also will change.

Task 4

Find all the terms and abbreviations given in the text,

write them down and give their meanings.

Task 5

Give a written translation of the extract beginning

with " When' electronics came along..." and ending "...in a digital. (rather than analog) domain” and the extract beginning with " This system is called packet..." and ending "... 100 percent efficient". While making your translation you may use a dictionary.

Text 5

Transmission Media.

There are four types of media that can be used in transmitting information in the telecommunications world:

-copper wire;

-coaxial cable (actually an adaptation of copper wire);

-fiber;

-wireless.

In days of old, copper wire was the only means of transmitting information. Technically known as un­shielded twisted pair (DTP), this consisted of a large number of pairs of copper wire of varying size in a cable. The cable did not have a shield and therefore the signal -

primarily the high-frequency part of the signal - was able to leak out. Also, the twisting on the copper pair was very casual, designed as much to identify which wires belonged to a pair as to handle transmission problems. However- this is the way it was done, and for voice communications it was quite satisfactory. Consequently, there are millions of miles of copper in the PSTN -miles that must be used.

Not only did the copper cable itself have limitations, but things were done to this cable to make it even more un­suitable for high-speed data transmission. These actions primarily took two forms:

loading - Load coils were frequently' added to
loops longer than 18, 000 feet. These load coils were es­sentially low-pass filters. That is, they passed without
attenuation all voice frequencies but effectively blocked
frequencies above the voice band. This is disas­trous for data communications, which depend on high
frequencies to achieve the desired speed of transmission.

bridge taps - A bridge tap is any unterminated
portion of a loop not in the direct talking path. A bridge
tap may be a used cable pair connected I at an intermediate point or an extension beyond the customer. For example, a drop wire that provided a second line to a home is left in place even after the second set of customer premises equipment (CPE) is removed. Records of this were not always kept and assigning a particular copper pair to a high-speed data circuit is far from a sure thing. Bridge taps do nasty things to data transmission.

Coaxial cable consists of a single strand of
copper running down the axis of the cable. This strand
is sepa­rated from the outer shielding by an insulator
made of foam or other dielectrics. A conductive shield covers the

-phragm varies the pressure on the granules of carbon. These granules both make more contacts and decrease the resistance of the granules or make fewer contacts and increase the resistance.

Sound waves produce oscillations of the same frequency as those of the sounding body. At this both the transmit­ter resistance and the current in the circuit will change.

1. Practise the following words and word combina­tions from the text: