Hi Melissa
No, that is not the case. The sensors are not broken at the same point in time. If you look back at the circuit I posted, the idea is one sensor is tripped before the next. However, when the first sensor is tripped, it remains tripped till the second sensor is tripped. That is how the count up or count down is derived. The system knows if people are coming or going (enter or exit). If for example on enter sensor 1 goes high we want sensor 1 to remain high when sensor 2 goes high, This is followed by sensor 1 going low and then sensor 2 going low. Again, look back at the circuit I posted and think about the logic the gates perform. That should make it clear.
This is how the direction of travel is established resulting in a count up (entering) or a count down (exiting).
Ron