Interval signal

An interval signal is a characteristic sound or musical phrase used in international broadcasting and by some domestic broadcasters. It serves several purposes:

• It assists a listener to tune his or her radio to the correct frequency for the station.
• 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.

The practice began in Europe in the 1920s and 1930s and was carried over into shortwave broadcasts. The use of interval signals has declined with the advent of digital tuning systems, but has not vanished.

Broadcasting Services and Interval Signals

BBC World Service in English: Bow Bells
Radio Australia: Chorus of Waltzing Matilda on chimes
Radio Canada International: First four bars of O Canada played on a piano
Radio France Internationale: Electronic-disco, cumulating in the last 8 measures of the Marseillaise
Radio Moscow (former service of the Soviet Union): Moscow Nights
Voice of America: Yankee Doodle played by a brass band
Voice of Russia: Chime version of chorus from Muggorsky's Pictures at an Exhibition