Chapter 7
DS0 VF Test Commands
Description of VF test commands
CT-650 Command-Line Reference Guide
Release 9.4
75
Peak-to-
average
ratio (P/AR)
PAR <
>
Measures the P/AR rating of a channel. During
this test, the CT-650 transmits a complex pulse
train with known peak-to-average ratio. Distor-
tions in the channel modify the P/AR signal.
Delay distortion, for example, causes the pulses
to spread in time as the different frequencies
experience different delays. This delay
decreases the peak-to-average ratio. When the
signal is received, the test system measures its
peak-to-average ratio and displays the results in
terms of P/AR units. The results range from 0 to
100 P/AR, with 100 meaning no degradation.
This test is not available when testing signaling.
Phase jitter
Phase_Jitter <
>
>
Determines if there is a deviation or fluctuation
in the “zero crossing” of a sine wave for a signal
from the nominal or optimum position in time.
Typically, phase jitter in carrier systems is
caused by inadequate filtering of the power sup-
plies. This low frequency interference causes
the unwanted angular modulation of a signal or
phase jitter. The CT-650 conducts the measure-
ment using a 1004 Hz tone in two bands: 20–
300 Hz and 5–300 Hz bands. Since phase jitter
affects the zero crossings of a signal with
respect to time (either delaying the crossing or
accelerating the crossing), it is expressed in
degrees peak-to-peak.
Quiet termi-
nation
Quiet_Term
The Quiet Termination test transmits quiet
(0xFE) on the line, compliant with IEEE-743.
This test does not display results.
Table 4
VF measure tests (Continued)
Test
Syntax
Description
Summary of Contents for CT-650
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