diff --git a/hobu_alert_system_control/app.js b/hobu_alert_system_control/app.js
index eaa931a..92a700c 100644
--- a/hobu_alert_system_control/app.js
+++ b/hobu_alert_system_control/app.js
@@ -11,6 +11,7 @@ var lastTagID = '';
 var timeOutForHoldingLastTagID = null;
 const timeOutForHoldingLastTagIDInMillis = Conf.rfid.timeout;
 var currentActionState = 0;
+var deviceList = null;
 
 
 Helper.each(Conf.items, function(item) {
@@ -201,13 +202,11 @@ function doActionOnRFIDCallback(key) {
   switch(currentActionState) {
     case 0:
       // deactivate alarm system
-      Log.log( 'deactivate alarm system' );
-      deactivateAlarmSystem();
+      deactivateAlarmSystem(key);
       break;
     case 1:
       // activate alarm system
-      Log.log( 'activate alarm system' );
-      activateAlarmSystem();
+      activateAlarmSystem(key);
       break;
     default:
       // nothing to do
@@ -215,14 +214,41 @@ function doActionOnRFIDCallback(key) {
 }
 
 /* private */
-function activateAlarmSystem() {
-  msg = '{type:"set_alarm_system_state", data:{state:"F111"}}';
-  send(msg);
+function isKnownCard(uuid, callbackIfSo) {
+  if(Helper.isDefinedAndNotNull(deviceList)) {
+    var filterResultDevices = deviceList.filter(function(entry) { return entry.details.uuid === uuid; });
+    Log.inspect('check for ' + uuid + ' in ' + filterResultDevices.length + ' devices', filterResultDevices);
+    if(Helper.isDefinedAndNotNull(filterResultDevices) && filterResultDevices.length > 0) {
+      callbackIfSo();
+    } else {
+      Log.debug('No device for ' + uuid)
+    }
+  } else {
+    Log.debug('No devices');
+  }
 }
 
 /* private */
-function deactivateAlarmSystem() {
-  msg = '{type:"set_alarm_system_state", data:{state:"F222"}}';
+function activateAlarmSystem(key) {
+  isKnownCard(key, function() {
+    Log.log( 'activate alarm system' );
+    msg = '{type:"set_alarm_system_state", data:{state:"F111"}}';
+    send(msg);
+  });
+}
+
+/* private */
+function deactivateAlarmSystem(key) {
+  isKnownCard(key, function() {
+    Log.log( 'deactivate alarm system' );
+    msg = '{type:"set_alarm_system_state", data:{state:"F222"}}';
+    send(msg);
+  });
+  
+}
+
+function fetchDeviceList() {
+  msg = '{type:"get_device_list"}';
   send(msg);
 }
 
@@ -240,7 +266,7 @@ var openWebSocket = function() {
   
   ws.on('open', function() {
     Log.log('ws open');
-    ws.send(Date.now().toString(), {mask: true});
+    fetchDeviceList();
   });
   
   ws.on('close', function() {
@@ -248,10 +274,22 @@ var openWebSocket = function() {
     openWebSocket();
   });
   
-  ws.on('message', function incoming(data, flags) {
+  ws.on('message', function incoming(rawData, flags) {
     // flags.binary will be set if a binary data is received.
     // flags.masked will be set if the data was masked.
-    Log.inspect('data', data);
+    const obj = JSON.parse(rawData);
+    const type = obj.data.type;
+    const data = obj.data.data;
+    
+    switch(type) {
+      case 'get_device_list':
+        const devices = data.result.filter(function(entry) { return entry.category.name === 'rfid_card' });
+        deviceList = devices;
+        Log.inspect('Devices', deviceList);
+        break;
+      default:
+        // nothing to do
+    }
   });
 }
 openWebSocket();
\ No newline at end of file