void setup() {
  Serial.begin(9600);
  for (int thisPin = 2; thisPin < 4; thisPin++) {
    pinMode(thisPin, OUTPUT);
  }
}

void loop() {
  Serial.println();
  //delay(init);
  if (Serial.available() > 0) {
    int inByte = Serial.read();
    switch (inByte) {
      case 'a':
        digitalWrite(2, HIGH);
        digitalWrite(3, LOW);
        digitalWrite(4, LOW);
        Serial.println("Relay 9 V Aktif");
        break;
      case 'b':
        digitalWrite(2, LOW);
        digitalWrite(3, HIGH);
        digitalWrite(4, LOW);
        Serial.println("Relay 12 V Aktif");
        break;
      case 'c':
        digitalWrite(2, LOW);
        digitalWrite(3, LOW);
        digitalWrite(4, HIGH);
        Serial.println("Relay 23 V Aktif");
        break;
      default:
      //digitalWrite(2, LOW);
      //digitalWrite(3, LOW);
      //digitalWrite(4, LOW);
      Serial.println("SEMUA RELAY MATI");
      break;
      //default:
       // turn all the LEDs off:
       // for (int thisPin = 2; thisPin < 4; thisPin++) {
       //  digitalWrite(thisPin, LOW);
       //   Serial.println("Semua Relay Mati");
       //}
    }
  }
}