On mobile phones, a ringtone is a brief audio file played to indicate an incoming call. A contemporary ringtone might consist of several bars of a familiar musical tune. Such ringtones are popular because, in a crowd of people with many cellular phone sets, they make it easy to tell whose phone is calling out for attention. The proliferation of cellular telephones in recent years has given rise to a wide variety of ringtones.
The earliest usage of ringtone (or ring tone ) is for the tone a caller hears indicating that the phone at the recipient's end is ringing. (Somewhat confusingly, this meaning is also called ringback .) On a traditional phone, the tone is sent back in between the ring sequence at the receiving end. The pulsing rate is one on, two off from a 3-phase generator with each call using a single phase. The called and calling phones would not necessarily use the same phase, so if you wanted to ring someone's phone (for example, to wake them up), you would need to hear it ringing for a full cycle to make sure that the phone actually rang at the other end.