Simultaneous Call Tutorial

This tutorial describes how to handle two call with the telephony API for applications.

Context

This state diagram shows how to dial or answer one or two calls at a time.

Figure: Simultaneous Call State Diagram

The boxes are states. The enumeration value in each box is the status of the voice line. Voice line status describes these states and their meaning. The arrows show events that trigger a change of state. In these events, a word in bold indicates a CTelephony method that you can call.

Steps

1. 1. check the Voice line status for other calls

      • if the line is Idle (CTelephony::EStatusIdle) then no calls are in progress

      • if the line is on hold (CTelephony::EStatusHold) then there is another call in progress, but it is on hold and you can still dial or answer a second call. Now go to point four below

      • if another call is active, you must wait until it completes before you can dial or receive a call.

   2. Dial a call while no calls are in progress, the line's status is CTelephony::EStatusIdle. To dial a call, use CTelephony::DialNewCall(). If dialling was successful and the remote party answers the call then the line's status will become CTelephony::EStatusConnected.

   3. Answer a call while no calls are in progress, the line's status is CTelephony::EStatusIdle. When a remote party calls your phone, the voice line's status will change to CTelephony::EStatusRinging. When the status is CTelephony::EStatusRinging, use CTelephony::AnswerIncomingCall() to answer the call. The status will change to CTelephony::EStatusConnected and the phone user can talk to the remote party.

   4. Terminate the call

   5. detect Remote Termination of a call

   6. Hold a Call

   7. Resume a call

   8. Send DTMF tones down the line

   9. Line and call information

   10. Answer a second call at some point, a remote party might try to ring your phone. It is answered in the same way as the first The voice line state will change to CTelephony::EStatusRinging. You can receive notification when this occurs; see Detect an incoming call. Before answering the second call, you must put the original call on hold. This is shown in the diagram above.

   11. Dial a second call you can also dial a second call in the same way as the first. Once again, you must put your original call on hold before dialling the second call

   12. a CTelephony::TCallId will be given to you when you successfully connect a second call. You will also have a CTelephony::TCallId from the first call. Now you will be the owner of two calls: at any one time, one will always be active and one will always be on hold. Now you can:

       • Terminate either call. If you terminate the active call then you will be left with a call on hold. If you terminate the on-hold call then you will be left with an active call.

       • Detect remote party terminating either call. Once again, if the active call ends then you will be left with a call on hold and vice versa.

       • Swap held and active calls.