خاصیت AutoDesconnect رو برابر false کنید


Private Sub KDPhone1_OnCallState(ByVal CallState As KDTele.TxCallState, ByVal Param1 As Long, ByVal Param2 As Long, ByVal CallHandle As Long)
If CallState = csRingBack Then
'خط داخلي مشغول مي باشد
End If
End Sub