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AM5(e) Classic Instruction Manual
6.6.2 Test Setup for S/N Ratio: For S/N Ratio measurement there must be a hold-tone
signal on the measured circuit. For end-to-end tests using AM5(e) Classic units,
the far-end unit SEND function should be set to 1004 Hz at a level of greater than
-40 dBm, while the near-end unit MEASURE function is set to S/N RATIO
(Refer to Figures 5-3, 5-4, and 5-5 for typical locations of equipment).
Where a responder is installed at the far-end, an external handset should be
connected to the DIAL terminals, the DIAL function selected, and the
responder's number called. When the responder answers, send the appropriate
code to put it into the "send 1004 Hz" mode.
For loopback tests, one AM5(e) Classic is used. The SEND selection is 1004 Hz
and the MEASURE selection is NOISE W/T.
6.6.3 Noise Weighting Filters:
measurements (CMSG for the AM5 Classic and PSHO for the AM5e Classic) are
normally used. Other filters may be selected by the left FILTER key to "weight"
the measurement over the band of frequencies that is important for the circuit.
On an AM5e Classic, two of the filter selections also select the Q-Peak detector.
The remaining filters provide RMS detection. Filters are described in detail in
Sections 7 and 8. A summary of filter types will also be found in sub-section
3.3.17.
6.7
IMPULSE NOISE WITHOUT TONE (IMP NOISE) or
IMPULSE NOISE WITH TONE (IMP N W/T)
6.7.1 General Description of Impulse Noise Measurement: Impulse noise testing is a
timed study which counts and stores the number of noise pulses that exceed
each of three levels (thresholds). The use of a holding tone is optional for
impulse noise tests, and this description applies to either selection.
NOTE: Information on setup for noise tests and filters is provided in sub-sections
6.7.4 through 6.7.6.
The time over which the test will be run is set by a duration parameter ("dur").
The lowest level noise threshold is set by the impulse threshold ("iTHd")
parameter.
The two higher-level thresholds are set by the delta threshold ("idLT")
parameter. The delta determines the level interval between the thresholds and
can be set at 2, 4, or 6 dB. To control the way that the pulses are counted, a
blanking interval parameter ("bLnC") is also provided. This parameter is used
by the blanking interval counter.
When a pulse first exceeds a threshold, it is counted. Then the blanking interval
counter starts. While the blanking interval is in effect, no further pulses will be
counted. The purpose of the blanking interval is to minimize the effect of ringing
on the count by providing a time for the ringing to die down.
November 19, 1997
(18-0047)
The default filter selection for S/N Ratio
Page 6-8
MEASURE FUNCTIONS
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•
IMP
I M P N
W/T
NOISE
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