void setup() {
  // put your setup code here, to run once:
pinMode(4, OUTPUT); //connected to output device in gate 4
}

void loop() {
  // put your main code here, to run repeatedly:
tone(4,2000); //frequency 2000
delay(500); //play for 0.5 seconds
tone(4,4000); //frequency 4000
delay(1000); //play for 1 second
noTone(4); //stop tone
delay(2000); //for 2 seconds
}