Ringback, or ringback tone, is the signaling tone played to the calling party while the network attempts to connect the call. It reassures the caller that the network is actively alerting the destination. Crucially, the ringback tone is generated by the network switch or PBX closest to the destination, not by the receiving phone itself, and its frequency and cadence vary by country.
Heard on the job
The SIP trace shows we're sending a 180 Ringing response, but the carrier isn't generating the ringback tone for the caller.
Insider tip
Hearing ringback does not mean the physical phone is actually ringing; it only means the terminating switch is attempting to ring the line.
Also heard as
- ringback tone
- RBT