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S/N
"S/N" stands for the signal-to-noise ratio. It is also called the SN ratio.
(For details, see this chapter, 5. S/N.)
2.2.2 Characteristics of exchange
(1) Step-By-Step (SXS)
Noise or Short breaks are more likely to occur as these exchange has many
mechanical contacts. This exchange is not suitable for facsimile transmis-
sion.
(2) Crossbar (XB) and Electronical Exchange (DEX)
These exchanges generate little noise or short breaks.
2.3
Factors of Telephone Line Deterioration
There are two main factors that cause the quality of facsimile transmis-
sions via telephone lines to deteriorate: usual factors (which always
present), unusual factors (which suddenly occurs), international communi-
cations and lightning. The following describes typical factors.
(For details, see this chapter, 7. Factors Which Cause Deterioration in
Quality of Facsimile Transmission.)
(1) Usual factors
(2) Unusual factors
A–6
• Transmission loss
• Attenuation distortion
• Group delay distortion
• Level variation
• White noise
• Crosstalk
• Frequency offset
• Phase jitter
• Impulse noise
• Short break
• Sudden level variation
• Phase hit
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