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 9bf6787..c5b1f0e 100644
--- a/doorbell/klingel_sender_nano_serial/klingel_sender_nano_serial.ino
+++ b/doorbell/klingel_sender_nano_serial/klingel_sender_nano_serial.ino
@@ -1,13 +1,14 @@
 /*  Klingel-Sensor auf Arduino Nano ATmega168
  * 
  *  https://www.arduino.cc/en/Tutorial/BuiltInExamples/Button
+ *  https://elektro.turanis.de/html/prj035/index.html
  * 
  *  D2  -------------
  *          |       |
- *        Button    |
+ *        10kOhm    |
  *          |       |
  *  +5V -----       |
- *               10kOhm
+ *                Button
  *                  |
  *  GND -------------
  */
@@ -29,17 +30,17 @@ void setup() {
 void loop() {
   int val = digitalRead(buttonPin);
 
-  if (val == HIGH) {
+  if (val == LOW) {
     delay(flare_threshold); // catch flares
     val = digitalRead(buttonPin);
     
-    if (val == HIGH && active == false) {
+    if (val == LOW && active == false) {
       Serial.println("RING");
       digitalWrite(ledPin, HIGH);
       active = true;
       delay(ring_delay);
     }
-    else if (val == LOW) {
+    else if (val == HIGH) {
       Serial.print("flare (<");
       Serial.print(flare_threshold);
       Serial.println(")");