interval signal

An interval signal, or tuning signal, is a characteristic sound or musical phrase used in international broadcasting and by some domestic broadcasters, played before commencement or during breaks in transmission, but most commonly between programmes in different languages. It serves several purposes:

• It assists a listener to tune his or her radio to the correct frequency of the station. This is because most older and cheaper radio receivers do not have digital frequency readout.
• It informs other stations that the frequency is in use.
• It serves as a station identifier even if the language used in the subsequent broadcast is not one the listener understands.