International call progress tones for IP-PBX and VoIP telephony

Telephone Line Signalling

Dial tone

  • A tone advising that the exchange is ready to receive call information and inviting the user to start sending call information.
  • In most countries, the dial tone is continuous. In a few countries, it is a slow period tone (where the On period is shorter than the Off period).
  • The tone consists of either a single tone or a combination of up to three tones. When a single tone is used, it may be modulated by a lower frequency tone.
  • The most prevalent, by country, is 425 Hz, continuous.

Search for Dial tones in the World Tone Database
Back to guide
Related product: CPT-Master tone generator app