Semaphore is a visual communications system using which one can send messages over a large distance. In a sense earliest form of semaphore were the smoke signals or waving flags/fire torches used by the pre-medieval/medieval armies during the battles.
The first scientific semaphore system that could carry a message 143 miles (230 km) from Lille to Paris was designed in in 1792 by Claude Chappe, a French engineer. It was had set of arms, pivoted on a post and the positions of the arms determined the meaning of the message. Messages were read by a telescope on a tower and re-transmitted to next tower. Similar method was adopted by other countries also (Ref: Wikipedia). However such a system of communication became obsolete after advent of telegraph system in 1850.
Railway signalling system using position of metal arms/lights is a variant of of Chappe's semaphore and is still used today. Hand held semaphore lights/flags are also used even now to guide naval ships/aircrafts at the ports/airports.
_______________________________________________________________World's largest semaphore is installed on the top 18th and 19th floors of the head quarters of Adobe Systems at Almaden Tower, San Jose, California. The art work known as "San Jose Semaphore" was installed by Adobe Systems in collaboration with the City of San Jose's public art programme.
Designed by by Ben Rubin, it is composed of four LED discs which seems to "rotate" to transmit a message. The rotating discs, bisected by a dark band, pause in four different positions (horizontal, 45 degree, vertical and 315 degrees) to communicate textual coded information. Four disks having four positions each, can convey 256 characters/words.
Each disk of the giant semaphore is 3 metres (10 feet) round and total length of the display is 21.3 metres (70-feet). The virtual disks rotate every 7.2 seconds.
San Jose Semaphore began its transmission on August 7, 2006 and a challenge was announced to read its coded message. It was finally deciphered on August 14, 2007. The semaphore was transmitting text from "The Crying of Lot 49" - a novel by American novelist Thomas Pynchon.
Coded text from the novel continues to be displayed even now, however a simultaneous broadcast of the soundtrack of the displayed text, by a low-power radio, has also been started to enable the viewers to hear the text being displayed.
Image from Picasaweb is by Petr
Image from Flickr is by Nat W
View location in Google Earth Google Maps & Street View
Main source of info and more info:
Credits: I am thankful to Betty Jones, who e-mailed me a link to "50 Greenest Buildings Around the World". Adobe Systems' Alamaden Tower, where this unique semaphore is installed, is a LEED-certified platinum building.
No comments:
Post a Comment
Please feel free to write your comments but remember that the same are moderated. So please do not post SPAM comments i.e. your business links here including surrogate links.
Comments containing SPAM are liable for rejection.