Copy of `University of Oxford - Telegraph history`
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University of Oxford - Telegraph history
Category: Electronics and Engineering > Telegraph
Date & country: 15/12/2007, UK
Words: 151
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Generator A device that produces electricity, particularly one that converts mechanical energy into electrical energy.
Galvanometer An instrument used to detect, measure, and determine the existence, direction and intensity of small electric (or galvanic) currents by means of the mechanical effects produced by a current-carrying coil in a magnetic field.
Galena A lustrous, blue-gray lead ore mineral, usually crystallised in cubes. Galena crystals were commonly used in ‘crystal` radio sets.
Flange A projecting flat rim, collar, or rib, used to strengthen an object, to guide it, to keep it in place or to assist in its attachment to another object.
Frequency The measurement of the number of time that an event occurs per unit of time. The standard unit of frequency is the hertz (Hz.).
Filament A radio valve (or tube) component, more commonly referred to as a cathode (US).
farad The standard unit of capacitance, named after Michael Faraday, represented by the symbol F. One farad is when one Coulomb of stored charge causes a potential difference of one Volt across its terminals.
Embosser A device which impresses in relief the image upon the stamp face on the stamped paper or document.
Enamel A vitreous, sometimes semi-transparent or opaque, glasslike material applied by heat to metallic, glass or ceramic surfaces. Commonly used to form a glossy or brilliant hard-wearing surface.
Element A radio valve (or tube) component, more commonly referred to as an electrode (US).
Electrode A conductor by means of which electricity enters or leaves a medium. Common examples include an anode or cathode.
Dynamo A machine that converts mechanical energy into electric current by rotating conductors (usually copper coils) in a magnetic field. Also referred to as a D.C. generator.
Ebonite A hard, relatively inelastic compound produced by the vulcanisation of rubber and sulphur, commonly used as an electrical insulating material.
Dull Emitter A radio valve (or tube) in which the filament operates at a relatively low temperature, and hence does not glow brightly but instead glows a dull red colour.
Domestic Relating to household usage as opposed to commercial usage.
Direction-Finder A device used to find the location of a wireless-transmitting station. Initially developed by Bellini and Tosi in 1907, the sets were later developed by the Marconi Company and were used by both sides during WWI. The sets took advantage of improved receiving equipment technology and directional characteristics of the loop antenna to discover the direction of a radio signal. By taking direction-finding ‘fixes` on enemy wireless transmissions from two or more locations, it was possible to find the approximate location of the enemy station. Also referred to as a goniometer or radiogoniometer.
Diode A radio valve (or tube) with only two basic electrodes, an anode and a cathode. Commonly used in radio demodulation, over-voltage protection, logic gates, and early wireless sets including ‘cat-whisker` and thermionic valve sets.
Crystal A crystalline piece of a semiconductor used in a wireless set on account of its properties of electrical conduction. Materials used include germanium, silicon, or galena.
Decremeter An electrical instrument used to measure the logarithmic decrement of an oscillatory circuit by an indirect method involving known changes of reactance in a circuit. As made by the Marconi Company from 1913 onwards.
Continuous Wave An electromagnetic wave with constant amplitude and frequency. This term was extended to denote a method in Wireless Telegraphy whereby the waveform to be transmitted was switched on and off, enabling a more efficient method of transmitting Morse code. In modern terms, a Type A0 wave.
Contact The part of an electrical circuit which, when connected, completes the electric circuit and permits the flow of electric current.
Condenser An apparatus for accumulating or increasing the intensity of an electric charge. Referred to in modern terms as a capacitor.
Coherer An early form of signal detector in wireless telegraphy, based around the effect that small particles of metal filings stick together (or ‘cohere`) when an electric field is present. A coherer circuit consisted of a basic electromagnetic wave detector for various wavelengths and a circuit that obtained signals from modulated radio waves. The coherer then ‘decoded` these signals.
Co-axial Sharing a common axis or core.
Cipher A system of encrypting a message by which units (usually letters) of ‘plain text` are arbitrarily transposed or substituted according to a pre-determined code (or cryptographic ‘key`) to produce ‘cipher text`. In theory, only those in possession of the key may be able to decrypt the message and reveal the original ‘plain text`.
Celluloid A solid flammable synthetic plastic material commonly used up to the middle of the 20th century.
Chromium A lustrous, hard, steel-gray metallic element, resistant to tarnish and corrosion, used in the hardening of alloys and in electro-plating.
Cathode The fundamental negatively-charged electrode (positive pole) in a radio valve or radio tube; opposite to anode. Sometimes referred to as a ‘filament`, especially in a diode.
Cat-whisker A fine adjustable wire, usually copper or gold, that connects to the detector in a crystal wireless receiver. While originally used to describe the mechanical component, the term was sometimes used to refer to the set itself.
Cast Iron A hard, brittle, non-malleable iron-carbon alloy which is so brittle that it cannot be wrought but must be shaped by casting. It is unsuitable for purposes where a sharp edge or flexibility is required; it is strong under compression, but not under tension. Historically and, to a lesser extent, contemporarily used for large structures, cookware and metal frames.
Carborundum Detector A device which, by taking advantage of certain properties of the carborundum crystal, converts A.C. (Alternating Current) into D.C. (Direct Current). In modern terms, a rectifier. The detector, as used in early wireless equipment, was fairly sensitive and reliable, and was quite popular especially in the United States.
Capacitor A device used to store and release electricity, usually as the result of a chemical action. Also referred to as a storage cell, a secondary cell, a condenser or an accumulator. A Leyden Jar was an early example of a capacitor.
Capacitance A unit measurement of a system's ability to store electrical charge.
Call Sign The conventional identifying code letters and/or numbers used to identify the sender of a wireless message or a radio transmitting station. Usually assigned by a national or international regulatory body.
Buzzer An electrical mechanism that produces an intermittent current and an audible buzzing sound, or series of sounds, when a call or signals are received.
Boxwood The wood of the box tree, a very tough close-grained yellow wood, commonly used in the manufacture of mathematical and assorted scientific instruments.
Base Pin A circular metal contact mounted in the base of a radio valve (or tube) to provide a connection to one of the internal electrodes.
Billi Condenser The first adjustable-type condenser, developed for use with tuned wireless receivers, which enabled sharp tuning to be employed in the receiving instrument. An experimental version was used by Marconi in his transatlantic transmission in December 1901; a full production version was brought into use in 1903 or early 1904.
Bakelite A trademarked thermosetting hardened synthetic resin material commonly used for electrical insulators, telephone receivers and assorted industrial manufacturing.
Baize A coarse cotton or woollen material, usually coloured bright green, used to imitate felt. Commonly used as covering on snooker tables and as a protective cushioning layer on the underside of heavy objects.
Auto-Alarm An automated wireless system that set off an alarm (usually a sound) in the case of receiving the Morse code signal for an emergency (usually S.O.S). This system was one outcome of the Titanic disaster and meant if a ship had only one wireless operator, he could sleep without fear of missing an emergency message.
Asbestos A mineral of fibrous texture, capable of being woven into a heat-resistant material; commonly used for fireproofing and thermal insulation in manufacturing and industry.
Anode The fundamental positively-charged electrode (negative pole) in a radio valve or radio tube; opposite to cathode. Sometimes referred to as a ‘plate`, especially in a diode.
Amplitude The maximum magnitude in displacement of a periodic or oscillating electrical wave; the noise strength of sound waves, in terms of pressure.
Amplification The application of an amplifier.
Amplifier An electronic device or circuit used to increase the magnitude of the voltage, current or power of an electronic signal.
Ammeter A low-resistance instrument that measures the force of electric current in units of Amperes.
Aerial Trimmer A trimmer for an aerial or ‘antenna`.
Alternator A synchronous Alternating Current (A.C.) electrical generator or dynamo.
Aerial Lead-In A lead-in from the aerial (or ‘antenna`) to the main device.
Accumulator An apparatus for accumulating or increasing the intensity of an electric charge. In modern terms, a capacitor.
