Receiver

#include <SPI.h>
#include <nRF24L01.h>
#include <RF24.h>

RF24 radio(7,8);

const byte address[6] = "00001";
const int buzzer = 4;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

  radio.begin();
  radio.openReadingPipe(0,address);
  radio.setPALevel(RF24_PA_MAX);
  radio.setDataRate(RF24_250KBPS);
  radio.startListening();
}

void loop() {
  byte gotnum = 0;

  if (radio.available()) {

    radio.read(&gotnum, sizeof(gotnum));
    Serial.println("OK");
    tone(buzzer, 500);
    delay(10);
    noTone(buzzer);
    delay(500);
    }
    else
    {
        Serial.println("__");
    }
  }