ZyXEL Communications U-336S User Manual page 145

signal point and the ideal signal point. For V.32/V.32bis, the
modem-measured S/N ratio is generally about 2 dB higher than
what is actually on the line because the modem rejects some of the
out-of-band noise. For V.22/22bis, the difference can be as high as
8 dB because the modem only uses part of the 3 KHz bandwidth
and rejects more than half of the voice band noise.
Received Signal Power Level (RX)
This reading is expressed in 0.1 dBm resolution. The modem
measured receiving signal power is generally within 1-2 dBm of the
actual value with relative accuracy. The receiver sensitivity
specification for your modem is -43 dBm. Strong signal power
could cause signal saturation in the channel and degrade the data
validity. To avoid this situation, decrease the transmission power of
the remote modem. For increased line operability, your modem's
transmission power level on a leased-line operation could be
adjusted from 0 dBm to -27 dBm. The default value is -9 dBm.
Phase Jitter (PJ)
This reading is expressed in peak-to-peak degrees for phase jitter in
the 20 to 300 Hz frequency range in 0.1 degree resolution.
Frequency Offset (FO)
Frequency offset is expressed in 0.1 Hz resolution. It is the
difference between the transmitted carrier frequency and the
received carrier frequency.
In the ON-LINE SCREEN 3 there are four counters recording the
action or reaction the modem took when the line condition
changed.
Retrain Granted (RG)
The count of the granting of the remote modem's retrain requests.
Each request is an indicator of bad receiving conditions.
Diagnostics & Troubleshooting 133