This is a file from the Wikimedia Commons

File:Post Office Engineers.jpg

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Original file(4,440 × 3,065 pixels, file size: 1.66 MB, MIME type: image/jpeg)

Summary[edit]

Description
English: British Post Office engineers inspect Guglielmo Marconi's wireless telegraphy (radio) equipment, during a demonstration on Flat Holm island, 13 May 1897. This was the world's first demonstration of the transmission of radio signals over open sea, between Lavernock Point and Flat Holm Island, a distance of 3 miles.

In the background is the spark-gap transmitter, an induction coil (right) that generates high voltage pulses that create sparks between the balls of the Righi spark gap (left), which excites oscillating currents in a wire antenna suspended aloft by the pole seen in the center, ratiating radio waves. Information is transmitted by switching the transmitter on and off rapidly using a switch called a telegraph key (not visible), spelling out text messages in Morse code.

In the foreground is the receiver. When receiving from the Lavernock station, the oscillating voltage from the antenna is applied to a coherer; a primitive radio wave detector consisting of a small tube containing two electrodes with metal filings between them. When a radio wave from a distant transmitter strikes the antenna and is applied to the coherer, the filings clump together and conduct electricity. A second circuit is attached to the coherer consisting of a battery which operates a relay (cylindrical objects at sides), which in turn sends a pulse of current to a Morse paper tape recorder (center). When a radio wave turns on the coherer, it sends a pulse to the recorder, which makes a mark on a paper tape. The Morse code message from the remote transmitter can be read from the tape, as the seated man is doing. The relays are contained within cylindrical metal shields to prevent their sparks from interfering with the sensitive coherer. Information from Retrospective:Radio waves across the water, TheFreeLibrary.com]

Date
Source Cardiff Council Flat Holm Project
Author Cardiff Council Flat Holm Project
Permission
(Reusing this file)
OTRS Wikimedia

This work is free and may be used by anyone for any purpose. If you wish to use this content, you do not need to request permission as long as you follow any licensing requirements mentioned on this page.

Wikimedia has received an e-mail confirming that the copyright holder has approved publication under the terms mentioned on this page. This correspondence has been reviewed by an OTRS member and stored in our permission archive. The correspondence is available to trusted volunteers as ticket #2008060810005124.

If you have questions about the archived correspondence, please use the OTRS noticeboard.


Ticket link: https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom&TicketNumber=2008060810005124

Licensing[edit]

w:en:Creative Commons
attribution
This file is licensed under the Creative Commons Attribution 3.0 Unported license.
You are free:
  • to share – to copy, distribute and transmit the work
  • to remix – to adapt the work
Under the following conditions:
  • attribution – You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).

Annotations This image is annotated: View the annotations at Commons

File history

Click on a date/time to view the file as it appeared at that time.

Date/TimeThumbnailDimensionsUserComment
current10:58, 8 May 2008Thumbnail for version as of 10:58, 8 May 20084,440 × 3,065 (1.66 MB)TR001{{Information |Description=Flat Holm island 1897 - Post Office Engineers inspect Marconi's equipment |Source=Cardiff Council Flat Holm Project |Date=1897 |Author=Cardiff Council Flat Holm Project |Permission=Creative Commons |other_versions= }} [[Categor
The following pages on the English Wikipedia link to this file (pages on other projects are not listed):

Global file usage

The following other wikis use this file: