Arduino DTMF

Working DTMF Arduino Mega2560

#include <Tone.h>

Tone freq1;
Tone freq2;

const int DTMF_freq1[] = { 1336, 1209, 1336, 1477, 1209, 1336, 1477, 1209, 1336, 1477 };
const int DTMF_freq2[] = {  941,  697,  697,  697,  770,  770,  770,  852,  852,  852 };

void setup()
{
  Serial.begin(9600);
  freq1.begin(5);
  freq2.begin(4);
}

void playDTMF(uint8_t number, long duration)
{
  freq1.play(DTMF_freq1[number], duration);
  freq2.play(DTMF_freq2[number], duration);
}


void loop()
{
  int i;
  uint8_t phone_number[] = { 0, 7, 4, 5, 3, 6 ,0, 6, 8, 5, 9 };

  for(i = 0; i < sizeof(phone_number); i ++)
  {
    playDTMF(phone_number[i], 100);
    delay(200);
  }
  

  delay(4000);
}