Tainet ITM-3296bis, User Manual

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4-2 GENERAL INFORMATION AND FEATURES
4.3 2W/4W Leased Line
We had talked modem operate in the previous section. There are two-wire leased lined
and four-wire leased line.
2W leased line achieves full duplex with only a pair of lines. There comes up the
problem of interference. In V.21, V.22, V.22bis operating modes, the T-288C
used
the frequency split method. Whereas, in V.32/V32bis/V.34 mode, it must provides
"echo cancellation", because originate and answer modems occupy the same
frequency band.
4W leased line offers two independently unilateral transmission channel, therefore, it
can achieve full duplex communication with less interference.
Obviously, the line quality of 4W leased line is better than that of 2W leased line.
However, the TAINET Network Series Modem does an excellent job with both 2W
and 4W leased lines and even dial line.
DTE MODEM MODEM DTE
∼
DTE
MODEM MODEM
DTE
∼
∼
2W Leased Line
4W Leased Line
FIG. 4-3: 2W/4W leased line.