This provides the convenience of a single telephone line bearing two numbers (prime number and duplex number). You can designate a distinctive ringing tone for each so that you know who is calling or for whom the call is intended before you pick up. The service also allows you to distinguish phone calls from faxes.
The Office of the Telecommunications Authority (OFTA) implemented the Unsolicited Electronic Messages Ordinance on December 22, 2007. Those who wish to resist unsolicited faxes can register their fax numbers on official do-not-call lists. To register your telephone or fax number onto any of the Do-not-call lists, you can make a call to the registration hotline 1835000 through the phone or fax machine of the number you wish to register.