The function allows you choosing a number that you want in order to
light up during the call to traditional telephones. You can also unlist the
number and it won’t light up.
Google Voice is a phone service provided by the makers of Gmail. It is an extremely well priced and competitive phone service that has VoIP rates which are literally pennies. In fact, if you are in the USA then calls are completely free throughout North America. The service also offers a number of other perks, such as voice transcription, conference calls, SMS to email, voicemail and even voicemail message to email services.