At a place where I worked a while back, they were in the process of introducing an "automatic gate" system that was described as detecting your "badge" with the badge anywhere on your person, visible or not.

Warnings were given that the detection worked best if you proceeded into, and through, the turnstile/booth at a normal walking pace. (A "stationary" badge was less effectively read.)

The turnstile consisted of a vertical post with horizontal iron pipes, about 2 inches in diameter and roughly a meter long, projecting across the entry way. The bars blocked the entire vertical distance from floor to ceiling of the "booth" with only about 10 inches between bars.

When your badge was recognized and verified, the vertical post "unlocked" so that you could push the bars around and pass through in typical turnstile fashion.

The cautious workers who approached too slowly did soon discover that it almost necessary to be walking at a fairly brisk pace in order for the turnstile to unlock reliably.

At proper pace when one approached, the turnstile unlocked quite reliably.

Except when it didn't...

Has any one other than my friend "Fred" had the experience of walking at 3.4+ mph into a fixed iron bar at nose height - - - on three consecutive mornings just before the first cup of coffee?

John