int i = 200;
const int ALARMSOUNDER = 3;     // the buzzer is on pin D3

void setup() {
  pinMode(ALARMSOUNDER, OUTPUT);
}

void loop() {
  for (i = 200; i < 700; i = i + 2) {   // sweep from a low tone up to a high tone
    tone(ALARMSOUNDER, i, 10);          // play the tone, changing every 10 ms
    delay(10);
  }
  for (i = 701; i > 200; i = i - 2) {   // sweep back down
    tone(ALARMSOUNDER, i, 10);
    delay(10);
  }
}