Case Communications syncro 1496, Reference Manual

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07 Round Trip Delay:
This is a measurement of the time taken for the data to be
transmitted once from local to remote and back again. By dividing
this delay by 2, the time taken for data to reach the remote end can be
obtained.
This information is particularly useful on internationally dialled
connections, to determine if the path chosen is satellite or cable.
Cable exhibits a much lower round trip delay time and may be more
suitable for systems that require a fast response time. Typical delays
for transatlantic satellites are in the order of 800 ms, and for
transatlantic cable 150 ms.
08 Far End Echo:
This is a measurement of the amount of transmitted signal reflected
back toward the transmitting modem from the remote end. Because
V.32 uses an echo-cancelling principle to transmit data, an echo level
that is too high can cause data errors and the modems to retrain,
causing breaks in service. A far-end echo figure of greater than –40
dBm would be a large amount of far-end echo.
09 Phase Roll:
Phase roll is caused by the combination of two effects, Far End Echo
and Frequency Shifts. The effect of phase roll will cause bursts of
errors to occur at regular intervals: the figure given will be a
measurement of the frequency offset on the communications line in
Hertz (Hz). V.32 will normally work with levels of phase roll up to 7
Hz; however this will also depend on the amount of far-end echo.
11 EQM Value:
Eye Quality Monitor (EQM) is a value produced by the modem to
indicate the quality of the received signal, and is a measurement of
deviation from the ideal signal. The larger the value, the worse the
received signal.
Note: This value is used to calculate other parameters and should not
be used on its own as a measurement of line quality.
12 Signal Quality:
This value is the most useful and most important, and should be used
if you are unsure of how to interpret the other values given. It is an
overall estimation of the line quality expressed as a numeric value
between 1 and 15. It is calculated from the EQM value and bit error
X450-310851 Issue 2 7-9 Rev.0