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30.03.2020 12:00 •  Английский язык

отмечаю лучшим решенияем TWISTED PAIR
Twisted pair cabling is a form of wiring in which two conductors (two halves of a single
circuit) are wound together for the purposes of canceling out electromagnetic interference (EMI)
from external sources; for instance, electromagnetic radiation from unshielded twisted pair
(UTP) cables, and crosstalk between neighboring pairs.
Twisting wires decrease interference because the loop area between the wires (which
determines the magnetic coupling into the signal) is reduced. In balanced pair operation, the two
wires typically carry equal and opposite signals (differential mode) which are combined by
addition at the destination. The common-mode noise from the two wires mostly cancel each
other in this addition because the two wires have similar amounts of EMI that are 180 degrees
out of phase. This results in the same effect as subtraction. Differential mode also reduces
electromagnetic radiation from the cable, along with the attenuation that it causes.
In contrast to FTP (foiled twisted pair) and STP (shielded twisted pair) cabling, UTP
(unshielded twisted pair) cable is not surrounded by any shielding. It is the primary wire type for
telephone usage and is very common for computer networking, especially as patch cables or
temporary network connections due to the high flexibility of the cables.
Twisted pair cables were first used in telephone systems by Alexander Graham Bell in
1881. By 1900, the entire American telephone line network was either twisted pair or open wire
with similar arrangements to guard against interference. Today, most of the millions of
kilometers of twisted pairs in the world are outdoor landlines, owned by telephone companies,
used for voice service, and only handled or even seen by telephone workers.
UTP cables are found in many Ethernet networks and telephone systems. For indoor
telephone applications, UTP is often grouped into sets of 25 pairs according to a standard 25-pair
color code originally developed by AT&T. A typical subset of these colors (white/blue,
blue/white, white/orange, orange/white) shows up in most UTP cables.
For urban outdoor telephone cables containing hundreds or thousands of pairs, the cable
is divided into smaller but identical bundles. Each bundle consists of twisted pairs that have
different twist rates. The bundles are in turn twisted together to make up the cable. Pairs having
the same twist rate within the cable can still experience some degree of crosstalk. Wire pairs are
selected carefully to minimize crosstalk within a large cable.
UTP cable is also the most common cable used in computer networking. Twisted pair
cabling is often used in data networks for short and medium length connections because of its
relatively lower costs compared to optical fiber and coaxial cable.
UTP cable is also finding increasing use in video applications, primarily in security
cameras. This is made possible by the fact that UTP cable bandwidth has improved to match the
baseband of television signals. While the video recorder most likely still has unbalanced BNC
connectors for standard coaxial cable, a balun is used to convert from 100-ohm balanced UTP to
75-ohm unbalanced. Only one pair is necessary for each video signal.

1. Answer the following questions.

1. What is twisted pair cabling?

2. Why are two conductors wired together?

3. What do twisting wires decrease?

4. What do two wires typically carry in balanced pair operation?

5. What do the two wires have?

6. What does it result in?

7. What does differential mode also reduce?

8. What isn't an unshielded twisted pair cable surrounded by?

9. Why is this wire type very common for computer networking?

10. When were twisted pair cables first used in telephone systems by Alexander Graham Bell?

2. Translate the following equivalents and memorize them.

Twisted pair, electromagnetic interference, unshielded twisted pair, crosstalk, to decrease interference, at the destination, to cancel, differential mode, to be surrounded by, computer networking, flexibility, outdoor landlines, identical bundles, security cameras, medium length connection, to match the baseband, twist rate.

3. Insert prepositions.

Keys: from, across, in, of, to, through, by.

1. Twisted pair cables were first used in telephone systems Alexander Graham Bell.

2. Electronic mail is a way sending messages and letters directly your computer to another computer.

3. You can send a letter your hundreds of friends all around the world a few seconds.

4. Subnetworks are arranged in three stages so that each call passes three subnetworks.

5. The cellular service lowers the cost of calls borders in the region.