JDS Uniphase CT-650, Reference Manual

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Chapter 7 DS0 VF Test Commands
Description of VF test commands
CT-650 Command-Line Reference Guide Release 9.4
73
Disable
echo can-
celler
Disable_EC
Disables the echo canceller feature of the hard-
ware by transmitting the echo canceller tone
before every VF test. This will ensure that echo
cancellers are properly disabled during VF test-
ing. Note that this has the same effect as select-
ing
Echo_Disable
split mode for the
VF_Split
command.
Echo return
loss
Echo_Return < tx_level >
Tests for the presence or absence of an “echo”
over a range of 300 Hz to 4000 Hz using a
weighted, swept-frequency sine wave signal.
The echo may be caused by an impedance mis-
match or discontinuity between two-wire and
four-wire circuits. The test transmits band-lim-
ited noise to measure return loss on VF circuits.
Impulse
noise
Impulse_Noise
< tx_level >
< ref_threshold >
< threshold_dif >
Counts the number of impulses that exceed
three different thresholds during a given period
of time, and also counts the number of dropouts
that occur during the test. To perform an
Impulse Noise test, the unit sends a holding
tone at a user-specified transmit level, then
uses a C-Message weighting filter on the
received signal. Impulses that exceed one or
more of the thresholds are counted. If an
impulse exceeds all thresholds, all counters are
incremented. The system also counts dropouts.
A dropout is counted if the signal drops by at
least 12 dB for at least four milliseconds. The
system does not count impulse noise hits during
a dropout.
Insertion
loss
Insertion_Loss
Determines the overall loss in dB on a given cir-
cuit using the 1004 Hz holding tone at -13.0
dBm. This test is essentially the same as the
Send or Receive Tone test, except that the
transmit level and frequency are fixed values
rather than data entered by the user.
Table 4 VF measure tests (Continued)
Test Syntax Description