Coherer

Abstract: Critical to the success of Marconi's pioneering work on radio telegraphy was the device needed to detect the radio telegraph messages on reception. Marconi finally settled on the "coherer." The invention of the device is often attributed to Oliver Lodge, a British physicist of the late 19th century. The detection properties of this device were, in fact, discovered by Edouard Branly, a French experimental physicist of the same period. As Dr. Dilhac makes clear in the following, Lodge himself attributed the signal detection properties of the coherer to Branly, coining the term coherer, and calling the device the "Branly coherer." The article clearly and succinctly discusses Branly's life, and describes the circumstances around which the coherer detection property was discovered by Branly. As pointed out by Dr. Dilhac, the physics behind the coherer long eluded scientists, and is just now, hopefully, becoming understood. During his life, Branly constantly denied being the inventor of radio, claiming that as a scientist he had only discovered an effect that had permitted others, like Popov, to develop wireless transmission. On the other hand, he was one of the earliest promoters of the remote control of equipment. During a largely publicized demonstration on 30 June 1905 at Palais de Chaillot in Paris he demonstrated the possibility to remotely and wirelessly turn light bulbs on and off or activate various electromechanical apparatus including motors. He made a publication on that topic in Compte-rendus a l'Academie des Sciences de Paris in March 1905. What is today called the Branly effect refers to a set of phenomena some of which were discovered before Branly. However, Branly was undoubtedly the first to publish about the effect of a spark that is, in modern words, the effect of an electromagnetic wave. Therefore, through the coherer and the demonstration that radio waves could easily be detected over long distances, he permitted early developments in wireless telecommunications. Finally and surprisingly, because of both its own intrinsic complexity and its potential involvement in modern technology, the Branly effect is today still a subject of investigation.

Abstract: The Italian Navy coherer was a receiving device used by Marconi in this first transatlantic transmission in 1901. A great controversy, which threatened to tarnish Marconi's reputation, arose concerning the invention of this coherer. The author re-examines the affair, and also includes some technical observations as to the coherer's precise mode of operation. >

Abstract: 12,039 Marconi, G June 2 [The following abridgment should replace that which appears on page 194 of the volume of this Class for the period AD 1893-96] Wireless signalling ; switches; transformers- Signals are sent by means of a Hertz radiator, and are received by a tuned receiver, including a tube of filings, coherer, c a series of the blocks and filing sections may be employed The tube is tapped by a trembler either continuously or on receipt of each signal ; in the latter case, the tapping is produced automatically either by the direct closure of the local circuit, or by a relay in the local circuit closing its circuits, one of which includes the trembler, and the other the receiving-instrument All the contacts are preferably bridged by non-inductive resistances, to prevent radiations due to sparking The transmitter consists preferably of two pairs of balls, which may be adjustable, the external balls being connected to the coil, while the central ones are placed near enough to spark, and are preferably separated by oil etc; these may consist of hemispheres having sparking-points on their flat surfaces set near together The transmitting and receiving apparatus may be placed in the foci of parabolic reflectors, or may be connected to large metal surfaces suspended as high as possible ; metal kites and balloons are also said to be employed The apparatus may also be connected to earth or water The induction coil is provided with a platinum contact rotatably mounted in the adjusting-screw and driven by a small motor

Abstract: We report the realization of a resettable resistive switching device based on a nanostructured film fabricated by supersonic cluster beam deposition of gold clusters on plain paper substrates. Through the application of suitable voltage ramps, we obtain, in the same device, either a complex pattern of resistive switchings, or reproducible and stable switchings between low resistance and high resistance states, with an amplitude up to five orders of magnitude. Our device retains a state of internal resistance following the history of the applied voltage similar to that reported for memristors. The two different switching regimes in the same device are both stable, the transition between them is reversible, and it can be controlled by applying voltage ramps or by mechanical deformation of the substrate. The device behavior can be related to the formation, growth and breaking of junctions between the loosely aggregated gold clusters forming the nanostructured films. The fact that our cluster-assembled device is mechanically resettable suggests that it can be considered as the analog of the coherer: a switching device based on metallic powders used for the first radio communication system.