The HC4000 is a Call Waiting Caller ID device that visually and audibly alerts you to an incoming call while you're online. The HotCall 4000 requires Call Waiting Caller ID service from your phone company. The LCD will also display the incoming caller's name and number. If you decide to take the call, just answer your phone. If you decide to ignore the call, the HC4000 will maintain your Internet connection and route the call to your phone company Voice Mail. This feature requires Voice Mail service from your phone company.