A ringtone or ring tone is the sound made by a telephone 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. For landline telephones, 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.

A telephone “ring” is the sound generated when there is an incoming telephone call. The term originated from the fact that early telephones had a ringing mechanism consisting of a bell and an electromagnetically-driven hammer, producing a ringing sound. The aforementioned electrical signal powered the electromagnet which would rapidly move and release the hammer, striking the bell. This "magneto" bell system is still in widespread use. The ringing signal sent to a customer's telephone is AC at 90 volts and 20 hertz in North America. In Europe it is around 60-90 volts AC at a frequency of 25 hertz

While the sound produced is still called a “ring”, more-recently manufactured telephones electronically produce a warbling, chirping, or other sound. Variation of the ring signal can be used to indicate characteristics of incoming calls (for example, rings with a shorter interval between them might be used to signal a call from a given number).