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However, this bandwidth is too narrow for data transmission which
requires a broad bandwidth such as facsimile transmission.
So, coding and high-speed modulation technologies are used for facsimiles
to transmit data at high speed in the limited narrow band.
2.2
Characteristics of Telephone Network Components
This item describes the characteristics of each component in a telephone
network. Various trouble may occur in these components.
2.2.1 Characteristics of transmission line
(1) Half-duplex communication system
• 2-wire cable system
External electrical noise can easily affect this system.
The frequency characteristics deteriorate according to the material and
length of the cable. Moreover, transmission loss may increase.
(2) Full-duplex communication system
• 4-wire cable system
Same trouble as for a 2-wire cable system may occur.
• Microwave radio relay system
The S/N may be affected by the weather.
• Satellite communication system
Echo (approx. 0.6 to 1.0 sec. including return) is generated.
The S/N may change due to the effect of the solar wind depending on the
season.
• Submarine coaxial cable system
Echo (approx. 0.3 sec. including return) is generated.
The leading section of the signal may be cut and the band is narrow (upper
limit 3 kHz).
Half-duplex communication
When using two communication terminals, directional communication is
performed alternately by this system.
Full-duplex communication
When using two communication terminals, directional communication is
performed simultaneously by this system.
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