Measuring Impulse Noise; Measuring Background Noise; Procedure; Calculating Expected Pulse Loss - Nortel M3110 Installation Manual

Page 302 of 504

Measuring Impulse Noise

Measuring Background Noise

Calculating Expected Pulse Loss

553-3001-367 Standard 3.00
Digital telephones line engineering
Use Procedure 51 on

Procedure 51

Measuring impulse noise

1 Measure impulse noise on selected lines during busy hours. Use an NE–
58B noise measurement set or the equivalent.
Note: The termination and weighting filter required are 135 ohm and
100 kHz, respectively, and the blanking interval is 25 µs.
2 Using Figure 48, determine that for a given loop loss and noise threshold
the impulse noise counts for each 15-minute interval are below the
corresponding curve.
Note 1: The values in Figure 48 were derived by assuming that the
counter has a count rate or 512 pulses per second.
Note 2: Because of the inaccuracy of the noise-measuring set, additional
errors can occur during the blanking interval, and the reading
consequently is lower than the actual measurement.
Use Procedure 52 on
Procedure 52

Measuring background noise

1 Measure background noise on the loop by using an NE-58B
noise-measuring set.
Note: The weighting and termination to be used are 100 kHz flat and 135
ohm, respectively.
2 Reject the loop being tested if the measured background noise is not less
than 51 dBrn.
Use Procedure 53 on
August 2005
page 302 to measure impulse noise.
page 302 to measure background noise.
page 304 to calculate expected pulse loss.