ZyXEL Communications U-336S User Manual page 147

measuring the distance between the demodulated 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.
Diagnostics & Troubleshooting 133