diff --git a/doorbell/klingel_sender_nano_serial/klingel_sender_nano_serial.ino b/doorbell/klingel_sender_nano_serial/klingel_sender_nano_serial.ino
index d03c3b5..113f4c6 100644
--- a/doorbell/klingel_sender_nano_serial/klingel_sender_nano_serial.ino
+++ b/doorbell/klingel_sender_nano_serial/klingel_sender_nano_serial.ino
@@ -1,12 +1,15 @@
-/*  Klingel-Sensor auf Arduino Nano ATmega168
- * 
+/*  Klingel-Sensor auf Arduino Nano ATmega168 plus zweiter Button für das Garagentor
+ *  Die Buttons sind über Optokoppler mit dem Arduino verbunden,
+ *  um den Spannungsabfall über die lange Leitung auszugleichen.
+ *  
  *  https://www.arduino.cc/en/Tutorial/BuiltInExamples/Button
  *  https://docs.arduino.cc/tutorials/generic/digital-input-pullup/
  */
 
 
 const int ledPin = LED_BUILTIN;
-const int buttonPin = 2; // Button connected to D2
+const int doorbellButtonPin = 2; // Button connected to D2
+const int buttonPin = 4; // Button connected to D4
 const int flare_threshold = 200;
 const int ring_delay = 250;
 
@@ -16,6 +19,7 @@ bool active = false;
 
 void setup() {
   pinMode(ledPin, OUTPUT);
+  pinMode(doorbellButtonPin, INPUT_PULLUP);
   pinMode(buttonPin, INPUT_PULLUP);
   Serial.begin(9600);
   Serial.println("Doorbell sensor");
@@ -23,28 +27,50 @@ void setup() {
 
 
 void loop() {
-  int val = digitalRead(buttonPin);
-
-
+  int val = digitalRead(doorbellButtonPin);
+  
+  if (val == LOW) {
+    delay(flare_threshold); // catch flares
+    val = digitalRead(doorbellButtonPin);
+    
+    if (val == LOW && active == false) {
+      Serial.println("RING");
+      active = true;
+      digitalWrite(ledPin, HIGH);
+      delay(ring_delay);
+    }
+    else if (val == HIGH) {
+      Serial.print("flare (< ");
+      Serial.print(flare_threshold);
+      Serial.println(" ms)");
+    }
+  }
+  else {
+    active = false;
+    digitalWrite(ledPin, LOW);
+  }
+  
+  
+  val = digitalRead(buttonPin);
+  
   if (val == LOW) {
     delay(flare_threshold); // catch flares
     val = digitalRead(buttonPin);
     
     if (val == LOW && active == false) {
-      Serial.println("RING");
-      digitalWrite(ledPin, HIGH);
+      Serial.println("CLICK");
       active = true;
+      digitalWrite(ledPin, HIGH);
       delay(ring_delay);
     }
     else if (val == HIGH) {
-      Serial.print("flare (<");
+      Serial.print("flare (< ");
       Serial.print(flare_threshold);
-      Serial.println(")");
+      Serial.println(" ms)");
     }
   }
   else {
-    digitalWrite(ledPin, LOW);
     active = false;
+    digitalWrite(ledPin, LOW);
   }
-}
-
+}
\ No newline at end of file