3Com 3106C User Manual page 105

These features are "persistent," that is, each one remains active until
you turn it off, as described in
If you forget which of the persistent features you have activated on
your telephone, log in to NBX NetSet > User Information > Feature
Settings. See "The NBX NetSet Utility"
on how to log in to the NBX NetSet
Exception: If you have activated one or more persistent features and your
mailbox has messages, you hear the New Messages Dial Tone whenever
you remove the handset from the charging unit, until you have deleted all
messages.
Table 11.
in Chapter 1
™ utility.
NBX Tones 105
for information