The Fire-Alarm Telegraph: A Box That Sends Its Own Address

// A fire-alarm signal box, after Channing and Farmer's circuit-wheel (US 17,355, 1857).
// Press the button and the box number goes out as two groups of pulses --
// the district, then the station -- three rounds, as one turn of the crank would send it.
const int BUTTON = 2;      // push button to GND (the crank)
const int BUZZER = 8;      // piezo buzzer (the bell at the central station)
const int LED = 13;        // on-board LED shows each pulse
const int DISTRICT = 3;    // first group of teeth
const int STATION = 5;     // second group of teeth
const unsigned long PULSE_MS = 150, GAP_MS = 250, GROUP_MS = 900, ROUND_MS = 2500;

void pulse() {
  digitalWrite(LED, HIGH);
  tone(BUZZER, 880);
  delay(PULSE_MS);
  noTone(BUZZER);
  digitalWrite(LED, LOW);
  delay(GAP_MS);
}

void group(int n) {
  for (int i = 0; i < n; i++) pulse();
  delay(GROUP_MS);
}

void setup() {
  pinMode(BUTTON, INPUT_PULLUP);
  pinMode(BUZZER, OUTPUT);
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  if (digitalRead(BUTTON) == LOW) {
    Serial.print("ALARM box ");
    Serial.print(DISTRICT);
    Serial.print("-");
    Serial.println(STATION);
    for (int r = 0; r < 3; r++) {
      group(DISTRICT);
      group(STATION);
      delay(ROUND_MS);
    }
  }
}