Tell-tale

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A tell-tale is a reference indicator or a sign that clearly signals that something else is true or is about to happen.

1 Sailing
2 Space
3 Railroad
4 Linguistics
5 References
6 External links

[edit] Sailing

In a nautical or sailing context a tell-tale is a piece of cloth or fabric that is tied or attached to a stay, one of several wires, that holds a mast in place on a sailboat. Usually there will be one tell-tale on the port stay and one on a starboard stay. When the wind blows the cloth waves much as a pennant or flag would flutter and gives you the relative direction of the wind. This aids navigation so you can adjust your direction with the rudder or a sail jibe or other sail adjustment to modify your direction.

Tell-tales can also be attached to a sail, used as a guide when trimming (adjusting) a sail. On the mainsail tell-tales are on the leech (aft edge) and when trimmed properly should be streaming backwards. On the jib there are tell-tales on both sides of the luff of the sail. As a general guide, the windward tell-tale should stream aft (backwards) with an occasional lift, the leeward front tell-tale should stream aft.

[edit] Space

The Phoenix spacecraft used a kind of weather rock, the Danish Aarhus' tell-tale project, in its Meteorological Station.^[1]^[2] It is a small tube that will be deflected by the martian wind. The science payload’s stereo camera will record images of the tell-tale that will be used to determine wind direction and speed.^[3]

[edit] Railroad

In a steam locomotive the tell-tales are longitudinal holes drilled in the stays of the firebox to provide early warning of corrosion.

A tell-tale is also a series of ropes suspended over the tracks above the height of a boxcar. These ropes are intended to give warning to a brakeman on the roof of the train that the train is approaching a low-clearance obstacle, such as a tunnel or a bridge. A Chesapeake and Ohio Railway tell-tale had 17 of these ropes hanging from a tube suspended across the track, the bottom of the ropes 12" lower than the height of the obstruction, and placed 100 to 300 feet before the obstruction.

[edit] Linguistics

In linguistics a tell-tale is a string of characters that occurs only within one language within a group of languages. A reader can be completely certain which language they are reading if he or she comes across a tell-tale. In this sense, a tell tale is a dead give away of what the language is.

More formally, a tell-tale of a member L of some language class is a finite subset of L such that no other language containing the subset in the class is a proper subset of L. In other words, a tell-tale is a finite subset that makes a language being a minimal consistent one in the class. The term is used in the field of artificial intelligence and machine language learning as well as linguistics. See also, Language identification in the limit