Voice dialing - definition
Voice dialing is a feature most modern phones support. It allows the user to dial a number by a voice command.
There are two ways this is done. The first way is for the user to record the commands in advance and then use them. This normally means that only the user who has recorded the commands may apply them.
The other kind of voice-dialing enabled phones use text recognition and no prerecording is required. When someone issues a command these devices simply match it to the nearest contact in the phone book.
This feature does not depend on the speaker and usually performs better than the former method. However, it is not commonly avaible, especially in older phones.