A ringtone or ring tone is the sound made by a mobile phone to indicate an incoming call or text message. The term is a misnomer, as it is often used to refer to any ring sound, almost all of which are not tones. The term is most often used to refer to the customizable sounds used on mobile phones.
A phone “rings” when its network indicates an incoming call and the phone thus alerts the user. The call signal can be an electric current generated by the switch to which the telephone is connected. For mobile phones, the network sends the phone a message indicating an incoming call.