How to use Two Ping Ultrasonic Sensor

I would like to have two ping ultrasonic sensor on my arduino. I can get one to work, but not the other. When I I have this code duration2 = pulseIn(pingPin2, HIGH); both sensor blinking light start to blink really slow and I get no data from neither one. Any help will appreciate.

Here is my code

/* Ping))) Sensor
  
   This sketch reads a PING))) ultrasonic rangefinder and returns the
   distance to the closest object in range. To do this, it sends a pulse
   to the sensor to initiate a reading, then listens for a pulse 
   to return.  The length of the returning pulse is proportional to 
   the distance of the object from the sensor.
     
   The circuit:
    * +V connection of the PING))) attached to +5V
    * GND connection of the PING))) attached to ground
    * SIG connection of the PING))) attached to digital pin 7

   http://www.arduino.cc/en/Tutorial/Ping
   
   created 3 Nov 2008
   by David A. Mellis
   modified 30 Aug 2011
   by Tom Igoe

   This example code is in the public domain.

 */

// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 7;
const int pingPin2 = 8;

void setup() {
  // initialize serial communication:
  Serial.begin(9600);
}

void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, duration2, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  //First Device
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);
  
  //Second Device
  pinMode(pingPin2, OUTPUT);
  digitalWrite(pingPin2, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin2, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin2, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  //First Device
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  //Second Device
  pinMode(pingPin2, INPUT);
  duration2 = pulseIn(pingPin2, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);
  
  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  
  delay(100);
}

long microsecondsToInches(long microseconds)
{
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds)
{
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}

I found the solution. I had both device mix in the code. I had all of the first device on top and the second device on the bottom.

void loop()
{
  // establish variables for duration of the ping, 
  // and the distance result in inches and centimeters:
  long duration, duration2, ping1_inches, ping1_cm, ping2_inches, ping2_cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  //First Device
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  //First Device
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  ping1_inches = microsecondsToInches(duration);
  ping1_cm = microsecondsToCentimeters(duration);
   if (ping1_inches < 10){
   
    Serial.print(" First Device ");
    Serial.print(ping1_inches);
    Serial.print("in, ");
    Serial.print(ping1_cm);
    Serial.print(" cm");
    Serial.println();
    delay(100);
   
 }
    
   //Second Device
  pinMode(pingPin2, OUTPUT);
  digitalWrite(pingPin2, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin2, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin2, LOW);
  //Second Device
  pinMode(pingPin2, INPUT);
  duration2 = pulseIn(pingPin2, HIGH);

  ping2_inches = microsecondsToInches(duration2);
  ping2_cm = microsecondsToCentimeters(duration2);

    
 if (ping2_inches < 10){
   
    Serial.print(" Second Device ");
    Serial.print(ping2_inches);
    Serial.print("in, ");
    Serial.print(ping2_cm);
    Serial.print(" cm");
    Serial.println();
    delay(100);
   
 }