const int buzzerPin = 4;
const int onDuration = 350;
const int periodDuration = 900;

unsigned long lastPeriodStart;

void setup () {

  pinMode(buzzerPin, OUTPUT);
 

}

void loop () {
  if (millis() - lastPeriodStart >= periodDuration) {
    lastPeriodStart += periodDuration;
    tone(buzzerPin, 1650, onDuration);
  }

  

}