Ringing (telephony)

Ringing is a telecommunication signal that causes a telephone to emit a noise (or other signal), indicating an incoming call. Historically, this entailed sending a high-voltage alternating current over the line to a customer’s telephone, which contained an electromagnetic bell. It is thus referred to as power ringing when distinguishing it from another signal, audible or tone ringing, which is sent to the caller’s handset to indicate that the recipient’s phone is in fact ringing.