What information do you want to send to the other board? You know, don't you, that Serial.write(), Serial.print() or Serial.println() would be used to send that information?
I am trying to send the input signal from board #1
What does "the input signal" mean? You can NOT send "signals" via an XBee. You send DATA.
You COULD send '0' to mean off and '1' to mean on. But, you have to send something via the Serial instance.
I am trying to send a high signal(0---->1) when I activate the Sharp IR sensor.
SHOW THE ONE LINE OF CODE THAT DOES THAT!
Let's try this. You know whether or not to turn the LED on. But, you do NOT control the switch. Your friend Tom does. Is there some part of "You need to tell Tom to turn the LED on or off" that seems too difficult for you to understand?
Is there some part of "You can only send data to Tom" that is hard to comprehend?
Is there some part of "You can only use Serial.print(), Serial.write(), or Serial.println() to send data to Tom" that is hard to fathom?