Tell-tale
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A tell-tale or telltale is an indicator, signal, or sign that conveys the status of a situation, mechanism, or system.
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[edit] Automotive
In a vehicle, a tell-tale is an indicator on or near the dashboard to inform the driver that a system or device is operating, switched on, or that a problem has occurred with the vehicle. The name itself indiates that it tells you a small story related to the vehicle. So a tell tale is a small story for the driver. For example: When you see the right or the left indicator it tells the driver a small tale that the vehicle is about to turn followed by its turning and finally it has completed the turn when the light goes off. Similarly, when there is an error, its tells you where the error is when possible.
[edit] Sailing
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In a nautical or sailing context a tell-tale, sometimes known as a tell-tail, is a piece of cloth or fabric that is tied or attached to a stay, any of several wires which hold a mast in place on a sailboat. Usually there will be one tell-tale on the port stay and one on a starboard stay.
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. If one tell-tale begins to spiral, it is indicating the sail has incorrect air flow on that side. To correct this the sail needs to move towards that side.
A tell-tale compass is a special compass installed in the ceiling of a cabin and which can be read from below, for example when one is resting on a bed, or from the side in a mirror showing the card's underside. According to Herman Melville's Moby Dick, a tell-tale refers to the cabin-compass, "because without going to the compass at the helm, the captain, while below, can inform himself of the course of the ship." [1]
[edit] Space
The Phoenix spacecraft contains a tell-tale, developed by the University of Aarhus in Denmark, as part of its Meteorological Station.[2][3] It is a small tube that is deflected by the martian wind. The science payload’s stereo camera recorded images of the tell-tale that are used to determine wind direction and speed.[4]
[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. On British Mark 1 carriages, a Tell Tale connects the emergency (communication) cord or chain to the train line to facilitate an emergency stop[5].
[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.
[edit] See also
[edit] References
- ^ Melville, Herman. Moby Dick. Illustrated by Rockwell Kent. Modern Library edition, 1992. Page 342.
- ^ Mars Simulation Laboratory, University of Aarhus, Denmark, The Telltale project, http://www.marslab.dk/TelltaleProject.html
- ^ Slashdot 27may2008, Mars Probe Brings the "Weather Rock" New Respect, http://science.slashdot.org/article.pl?sid=08/05/27/153240
- ^ Nasa Press Kit/May 2008, ed., Phoenix Landing Mission to the Martian Polar North, NASA, http://www.nasa.gov/pdf/226508main_phoenix-landing1.pdf
- ^ Parkin Keith, British Rail Mark 1 Coaches 1991
