/*A sketch to show SOS signal */

int led = 13;
int unit = 500;

// displaying S character
void displayS() {
 digitalWrite(led, HIGH);
 delay(unit);
 digitalWrite(led, LOW);
 delay(unit);
 digitalWrite(led, HIGH);
 delay(unit);
 digitalWrite(led, LOW);
 delay(unit);
 digitalWrite(led, HIGH);
 delay(unit);
 digitalWrite(led, LOW);
 delay(unit);
}

//dispalying O charachter
void displayO() {
  digitalWrite(led, HIGH);
  delay(3*unit);
  digitalWrite(led, LOW);
  delay(unit);
  digitalWrite(led, HIGH);
  delay(3*unit);
  digitalWrite(led, LOW);
  delay(unit);
  digitalWrite(led, HIGH);
  delay(3*unit);
  digitalWrite(led, LOW);
  delay(unit);
}

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

void loop() {
  displayS();
  displayO();
  displayS();
  delay(7*unit);
}