International call progress tones for IP-PBX and VoIP telephony
Telephone Line Signalling
Calling tone
- The calling tone is sent by the calling modem to indicate that a data or fax call is being placed.
- It is a slow period tone, where the On period is shorter than the Off period.
- For data, it is nominally 1300 Hz at 0.6/1.75 (on/off in seconds). For fax, it is nominally 1100 Hz at 0.5/3.0 (on/off in seconds).
Back to guide
