Intermodulation Distortion - Nortel Meridian 1 Succession 1000 Manual

Intermodulation distortion

Intermodulation distortion is caused by nonlinearities present in the
electric-to-electric transfer function of the PBX. This form of distortion
primarily affects data transmission.
Intermodulation distortion is measured by using the four-tone method that
employs two pairs of equal-level tones transmitted at a total, composite power
level of –13 dBm. One pair of tones uses 857 Hz and 863 Hz frequencies,
while the second pair uses 1372 Hz and 1388 Hz frequencies. The second-
and third-order products of distortion are denoted as R2 and R3, respectively.
The power levels for R2 and R3 (see Table 66) are expressed in decibels
below the received power level and are calculated as follows:
• R2 is the average power level measured in two different ranges of the
voiceband between 503 Hz and 537 Hz, and between 2223 Hz and
2257 Hz.
• R3 is the total power level in the frequency range between 1877 Hz
and 1923 Hz.
Table 66
Intermodulation distortion—µ-Law
Connection type
Line to line
Line to trunk
Trunk to trunk
Transmission characteristics—µ-Law
Distortion limits (dB)
below received level
R2
39
39
39
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Test-signal input
R3 level (dBm)
51 –9
51 –9 at line
–13 at trunk
51 –13
Transmission Parameters