One or both infrared beams are not working

• Check all the Gray Boxes, if there is a red light that beam is not working.

• Check alignment, the tripods may have moved out of alignment

• Check batteries, a rapid red light on a Black Box indicates its battery is out

• Bring the Black Box closer to the corresponding Gray box

• If the sun is shining into the window of the Gray box, swap the black and gray boxes so the Gray box is not facing the sun.