>>> Part 5 of 5...


3. Coder/decoder. The device which sits between the digital portion of the
network and the analog local loop and converts between analog and digital.

4. The physical connection between the central office and the home is two
individual copper wires of 24 or 26 gauge twisted about each other to
minimize crosstalk. It's length depends upon the distance from the home to
the central office but is normally less than 18,000 feet.

5. The network carries the two sides of a voice call in two separate
channels. However, the connection to the home is only two wires. The hybrid
converts between this separate channel system, referred to as four wire,
and the two wires serving the home.

6. A "symbol" is an information carrying token. In this 56 Kbps technology,
a symbol is a voltage level. In ordinary modem technology, a symbol is a
combination of amplitude and phase. The term "symbol" was adopted after the
original term, "baud", became corrupted in common usage.

7. The symbols in QAM space are created by simultaneously modulating a
carrier in amplitude and phase

8. A trellis code is a technique to improve the modem receiver's ability to
discriminate between two adjacent symbols.

9. However, TrueVoice can be disabled using the same techniques as are used
to disable echo suppressors.

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