1. Define (if necessary) the TAPI device on which the calls must be detected. Use the functions:
   

   tapiCapability	Returns the characteristics of a telephony device.
   tapiDevice	Selecciona el dispositivo TAPI que se utilizará durante las siguientes operaciones de telefonía: tapiDial, tapiListen.
   tapiDeviceList	Enumera los dispositivos compatibles con TAPI 2.0 y TAPI 3.1 instalados en el ordenador actual.
2. Start the detection of incoming calls with tapiListen. This function runs a specific WLanguage procedure. This procedure will be automatically run when an incoming call is detected.
3. In this procedure, you can:
   • find out the status of the call via the following constants:
     • telLigneOccupée: Line is currently busy.
     • telLigneDécrochée: The line is connected.
     • telLineNumber: Dialing in progress.
     • telLigneTonalité: Line receives dial tone
     • telLigneRaccrochée: The correspondent has hung up
     • telLineAttendAnswer: The call is dialed: search for the correspondent
     • telLigneSonnerie: Ringing tone in progress at the correspondent's address
     • telNewCall New call detected waiting to be answered or rejected.
     • telInformationAppel: Additional information (number presentation) is available at. In most cases, this information will be available after the fist ring.
   • manage the call via the following functions:
     • finding out the characteristics of the incoming call:
       

       tapiCallDuring	Devuelve la duración de la llamada (diferencia entre la fecha y hora de inicio de la llamada y la fecha y hora de finalización de la llamada).
       tapiCallEnd	Devuelve la fecha y hora de fin de llamada.
       tapiCallerID	Sirve para averiguar el número de teléfono llamante (el que llama).
       tapiCallIsOver	Permite saber si la llamada entrante o saliente ha finalizado.
       tapiCallStart	Devuelve la fecha y la hora del inicio de la llamada (llamada entrante o saliente).
     • perform specific operations:
       

       tapiAnswerCall	Responde a una llamada entrante detectada.
       tapiKeyPressed	Returns the history of the keys pressed on the phone keypad since the last call to tapiKeyPressed.
       tapiPlay	Plays a sound file (.WAV) for the specified line.
       tapiRecord	Graba la comunicación actual como archivo ".WAV".
       tapiSendKey	Permite simular el uso de las teclas del teléfono.
       tapiStop	Detiene la lectura de un mensaje pregrabado (tapiPlay).

       
       Caution:
       This WLanguage procedure being run in a thread, all the constraints of the threads must be complied with (no window opening, no timer management, no event management, ...). For more details, see Managing threads with WINDEV.
       We recommend that you limit the number of processes performed in this procedure. Indeed, during the duration of the call, the detection of the other calls (as well as all the telephony events) is frozen. If long processes must be performed, we advise you to process the call in the main thread of the application (see the example below).
4. To end the session for detecting the incoming calls, use tapiStopCallDetection.

Example used to manage the incoming calls in the main thread

• Code for declaring the global variables of the window used for call detection. The different events used to manage the calls in the main thread of the application are declared in this code.
  

  GLOBAL 
  gnEventID is int 
  // Implement an event to manage the incoming calls in popup 
  IF Event("DetectedCall", "*.*", "PhoneCall") = 0 THEN 
  	Error("Unable to manage the popup for call detection", ErrorInfo()) 
  END 
  IF Event("EndDetectedCall", "*.*", "EndPhoneCall") = 0 THEN 
  	Error("Unable to manage the popup for call detection", ErrorInfo()) 
  END 
  IF Event("DetectedCallIdentifier", "*.*", "PhoneCallInfo") = 0 THEN 
  	Error("Unable to manage the popup for call detection", ErrorInfo()) 
  END

• Window initialization code: this code starts the call detection procedure.
  

  // Start the service for call detection 
  IF tapiListen("IncomingCall", tapiOptionMediaModeFax, "CallDetection") THEN 
  	// The service for call detection is started 
  	Message("Call detection enabled") 
  ELSE 
  	// The service for call detection is not started 
  	 Error("Unable to start the call detection" + CR + ...
  			"Error details:"+ CR + ErrorInfo(errMessage)) 
  END

• Procedure for call detection:
  This procedure is used to detect the incoming calls.
  For each incoming call, the characteristics of the call are transmitted to the main thread by PostMessage.
  

  PROCEDURE CallDetection(nServiceID, nCallID, nStatus) 
  // WARNING: 
  // The processes performed by this procedure are called from a thread 
  // The display should be done via the main thread
  // (this is why PostMessage is used) 
  // The "Trace" function must be used to debug this process 
  // detection of incoming calls 
  SWITCH nStatus 
  	// Detect a new call: 
  	// Note: More information will be available after at least one ring 
  	CASE tapiNewCall: 
  	  // Signal to the main window that a new call is arriving 
  	  // to open a popup 
  	  PostMessage(Handle(Window_Call), "PhoneCall", nCallID, nStatus) 
  	  // Information about the call is available 
  	CASE tapiCallInformation: 
  	  // Signal to the main window that a new call is arriving 
  	  // to open a popup 
  	  PostMessage(Handle(Window_Call), "PhoneCallInfo", nCallID, nStatus) 
  	  // The line was hung up 
  	CASE tapiLineDisconnected: 
  	  // Signal to the main window that a new call is arriving 
  	  // to open a popup 
  	  PostMessage(Handle(Window_Call), "PhoneCallEnd", nCallID, nStatus) 
  END