int sensor=10;
void setup() {
  // put your setup code here, to run once:
pinMode(11, OUTPUT);
pinMode(A0, INPUT);
Serial.begin(9600);
}
int signal;
  signal=analogRead(A0);
  Serial.print(signal);
  if(signal<sensor){
    tone(13,700,250);
    Serial.println("Alram is activeted");

  }
  else{
    Serial.println("Alram is diactivated");
  }

void loop() {
  // put your main code here, to run repeatedly:
  

}