Entry and exit barriers
Gates and turnstiles are physical barriers to control the flow of people into an area, or between areas. In broad terms, “gates” are barriers that can open and close; they may be set to allow one person through at a time, or to be opened and closed to suit the circumstance. “Turnstiles” are rotating devices that allow one person through at a time.
Depending on the circumstance and intended mode of use, gates and turnstiles can be relatively small to act as a moderate barrier that is as much a demarcation. Alternatively, they may be quite substantial and make it difficult or impossible to pass except by following the correct procedure.
There is a great variety of gates and turnstile concepts, ranging from simple technical devices to sophisticated electronic units with embedded sensors and readers.