3Com 3C10402B Administrator's Manual page 411

United Kingdom ringing cadence is 2 rings within approximately 2
■
seconds followed by 2 seconds of silence.
United States busy tone is 0.75 seconds of tone followed by 0.75
■
seconds of silence.
To enable different regional settings:
1 Log on to the NBX NetSet utility using the administrator login ID and
password.
2 Click Country Settings > Regional Settings > Advanced Regional Settings.
3 See the online Help for more information.
Regional Settings 411