Tapping coherer



This photo was viewed 2 times and was downloaded in full size 0 times.

This photo was liked 0 times

Please login in order to see the source link


English: Drawing of a Branly coherer radio detector with a "tapper" or decoherer mechanism. Coherers were used in the first radio receivers during the wireless telegraphy era from about 1900 to 1910. The Branly coherer was a tube with two silver "plugs" or electrodes, with loose metal filings in the space between. When a radio signal from an antenna was applied across the electrodes, it caused the resistance of the filings to decrease, making the device conductive. The coherer was also connected in a DC circuit powered by a battery, with an earphone or a Morse paper tape recorder. When the coherer turned "on", it made a sound in the earphone or a mark on a paper tape, recording the code symbol received. However, the coherer remained in the conductive state after the radio signal disappeared. To prepare it to receive the next radio signal, the filings had to be mechanically disturbed to return the device to the nonconductive "off" state. This was done by a "tapper" or decoherer consisting of an electromagnet connected in the DC circuit. When the coherer turned on, the electromagnet attracted the arm with the metal ball to tap the coherer tube, returning the coherer to the nonconductive state.
Date 1917(1917)
Source Appeared as an illustration in the article "Radio Detector Development" by H. Winfield Secor, published in the January, 1917 issue of "The Electrical Experimenter". (Got it from Citizendium)
Author "The Electrical Experimenter" (Commercial publication.)
(Reusing this file)

Public domain in USA - published in USA prior to 1923


Public domain
This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1923. See this page for further explanation.
United States
This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the rule of the shorter term for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See Wikipedia:Public domain and Wikipedia:Copyrights for more details.
English: The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the twentieth century. It consisted of a tube or capsule containing two electrodes spaced a small distance apart, with metal filings in the space between them. It was a key enabling technology for radio, and was the first device used to detect radio signals in practical spark gap transmitter wireless telegraphy. Its operation is based upon the large resistance offered to the passage of electric current by loose metal filings being decreased under the influence of radio frequency alternating current. The coherer became the basis for radio reception around 1900, and remained in widespread use for about ten years. It saw commercial use again briefly in the mid 20th century in a few primitive radio-controlled toys that used spark-gap transmitter controllers. (?Coherer)
English: Coherer

Public Domain


Only registered users can post comments. Please login

EXIF data:
File name tapping_coherer.jpg
Size, bytes 81803
Mime type image/jpeg
The images at Free-Photos.biz come mainly from Wikimedia Commons or from our own production. The photos are either in the public domain, or licensed under free linceses: Free-Photos.biz license, GPL, Creative Commons or Free-Art license. Some very few other photos where uploaded to Free-Photos.biz by our users and released into the public domain or into free usage under another free license (like GPL etc.)

All photos in average size can be saved by everyone without registration (by right-clicking) - and all photos can be downloaded in full-size and without the big watermark by members (by left-clicking) (registration and free membership required).

While the copyright and licensing information supplied for each photo is believed to be accurate, Free-Photos.biz does not provide any warranty regarding the copyright status or correctness of licensing terms. If you decide to reuse the images from Free-Photos.biz, you should verify the copyright status of each image just as you would when obtaining images from other sources.

The use of depictions of living or deceased persons may be restricted in some jurisdictions by laws regarding personality rights. Such images are exhibited at Free-Photos.biz as works of art that serve higher artistic interests.

christianity portal