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A sally port is a secure, controlled entryway to a fortification or prison. The entrance is usually protected by some means, such as a fixed wall on the outside, parallel to the door—which must be circumvented to enter and prevents direct enemy fire from a distance. It may include two sets of doors that can be barred independently to further delay enemy penetration.
From around 1600 to 1900, a sally port was a sort of dock where boats picked up or dropped off ship crews from vessels anchored offshore. That meaning occasionally still occurs, especially in coastal Great Britain.
Etymology and historical usage
A sally, ultimately derived from Latin salīre (to jump), or "Salle" sortie, is a military maneuver, typically during a siege, made by a defending force to harass isolated or vulnerable attackers before retreating to their defenses. Sallies are a common way for besieged forces to reduce the strength and preparedness of a besieging army; a sally port is therefore essentially a door in a castle or city wall, that allows troops to make sallies without compromising the defensive strength of fortifications.
Targets for these raids included tools, which defenders could capture and use—and labor-intensive enemy works and equipment, such as trenches, mines, siege engines, and siege towers. Sometimes the defenders also attacked enemy laborers, and stole or destroyed the besiegers' beer and food supplies.
An extract from a nineteenth century dictionary of military terms describes a sally port thus:
... those underground passages, which lead from the inner to the outward works ; such as from the higher flank to the lower, to the tenailles, or the communication from the middle of the curtain to the ravelin. When they are constructed for the passage of men only, they are made with steps at the entrance, and outlet. They are about six feet wide, and 8 1/2 feet high. There is also a gutter or shore made under the sally-ports that are in the middle of the curtains, in order that the water which runs down the streets may pass into the ditch ; but this can only be done when they are wet ditches. When sally-ports serve.to carry guns through them for the out-works, instead of making them with steps, they must have a gradual slope, and be eight feet wide.
Comparison to unidirectional traffic-control mechanisms
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Sally ports, as in a modern police station or prison, are designed to prevent unauthorized traffic in both directions. In other situations it is desired to allow free movement in one direction while preventing it in the other. At exits from the sterile area of an airport, passengers are prevented from re-entering, either by human watchers or automatic devices. Municipal rapid transit systems with journey-independent fares, such as the New York subway system, commonly use turnstiles to similarly to permit entry only after payment of the fare, while not restricting exit. In systems such as the London Underground where the fare depends on the journey, passengers' tickets are read by turnstiles at both the entry and exit.
A sally port appears on the Coat of Arms of the Republic of Malta.
- "The continuing education program of the Royal City of Eoforwic presents". Members.tripod.com. Retrieved 2012-01-26.
- Charles James (1802). A new and enlarged military dictionary, or, Alphabetical explanation of technical terms: containing, among other matter, a succinct account of the different systems of fortification, tactics, &c. also the various French phrases and words .. Printed for T. Egerton at the Military Library.
- "Guard who let man in through exit at Newark Airport shown the exit".
- "Glass exit portals: Security to leave the airport". 2 December 2013.
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