Thanks for the info. I am using pair of infrared sensors on one side facing the transmitter on the other side, and all I want is the same pair of sensors to command a counter to increment by 1 if a person breaks them in one way (IN) or if the other way round that will mean exit and hence decrement the counter.I was thinking of coding the arduino board to check the sequence in which the sensors were tripped and then decide whether to increment or decrement count.
steffano.