Sony PCV-MXS20 - Manual (Page 95)

About the Modem
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About the Modem
Why doesn’t the modem’s Wake on Ring (WOR) feature work properly?
Your installed Lucent™ Win Modem does not support the Wake on Ring (WOR)
feature of the Microsoft® Windows® XP operating system. For optimal use,
Sony recommends that you do not change the preset modem settings. See the
Windows Help and Support Center for more details on the WOR feature.