This API is available on Firefox OS for internal applications only.

The onstatechange event handler of the TelephonyCall interface is a reference to a function to be called to handle the Telephony API's statechange event.

This event occurs whenever the value of TelephonyCall.state changes. The event handler is called with a CallEvent as its only parameter.


// Telephony object
var tel = navigator.mozTelephony;

// Place a call
tel.dial("123456789").then(function(call) {

  call.onstatechange = function(e) {
    console.log('Your call has changed state to ' +;


Specification Status Comment
Web Telephony Draft Draft.

Browser compatibility

For obvious reasons, support is primarily expected on mobile browsers.

Supported in Firefox OS 1.0.1.

See also