Turnstile

Turnstiles at Alewife subway station in Cambridge, Massachusetts

A turnstile, also called a baffle gate, is a form of gate which allows one person to pass at a time. It can also be made so as to enforce one-way traffic of people, and in addition, it can restrict passage to people who insert a coin, a ticket, a pass, or similar. Thus a turnstile can be used in the case of paid access (sometimes called a Faregate when used for this puropse) (e.g. public transport or a pay toilet), or to restrict access to authorized people.

The invention of the turnstile has been credited to Clarence Saunders, who used them in his first Piggly Wiggly store.

Turnstiles are also used for counting the numbers of people passing through a gate, even where payment is not involved.

Turnstiles were originally used, like other forms of stile, to allow human beings to pass whilst keeping sheep or other livestock penned in. Two passageways into Lincoln's Inn Fields in London have been named Great Turnstile and Little Turnstile for hundreds of years, harking back to the days when there was grazing there.

The first major use of turnstiles at a sporting venue was at Hampden Park in Glasgow, Scotland.

Turnstiles often use ratchet mechanisms to allow the rotation of the stile in one direction allowing input but preventing rotation in the other direction. They are often designed to operate only after a payment has been made, usually by inserting a coin or token in a slot, or by swiping an electronic card.

Mechanical turnstiles are less often used these days, with electronic gate and ticketing systems becoming more common.

A British turnstile used for public events in the late 1880s

In the first half of the twentieth century, it was common for entry to public lavatories in Britain to be controlled by turnstiles.

The High Entrance/Exit Turnstile (HEET), a larger version of the turnstile, similar in operation to a revolving door, is known as an "iron maiden", after the medieval torture device of the same name. [link] It is sometimes called a "Rotogate", especially in Chicago, where they are used at unstaffed exits of their El stations. [link] In Europe, however, "Rotogate" refers to a different kind of gate that isn't even a turnstile.

Other usage

The symbol [\vdash] has taken the name turnstile in mathematical logic because of its resemblance to a typical turnstile if viewed from above. The mathematical symbol was first used by Gottlob Frege in his Begriffsschrift; the latter article also describes how the symbol was created by Frege.

External link

[Page showing various designs of turnstiles] in the history of the New York subway system.

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