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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S.W Short Wave: a radio wavelength of relatively short wavelength, corresponding to between about 2,000kHz. and 25MHz.
R.F Radio Frequency: a frequency in the range within which radio waves may be transmitted, from about 3kHz to about 3GHz.
L.W Long Wave: A radio wave of greater than 1000 metres and, in modern usage, less than 10,000 metres.
M.W Medium Wave: A radio wave of between 300 and 3,000 kHz.
L.F Low Frequency: a radio frequency in the range 30-300KHz. See also H.F.
L.T Low Tension: a low degree of electromotive force or power. A term commonly used at the beginning of the 20th century. See also H.T.
I.F Intermediate Frequency: the frequency to which an incoming carrier wave is converted by the frequency changer of a superheterodyne receiver. About 455KHz (A.M.) or 10.7MHz (F.M.).
H.T High Tension: a high degree of electromotive force or power. A term commonly used at the beginning of the 20th century. See also L.T.
H.F High Frequency: a radio frequency in the range 3-30MHz. (3,000 kHz. â€` 30,000kHz.). See also L.F.
F.M Frequency Modulation: the system of radio transmission whereby the wave is modulated by variation of its frequency, i.e. the frequency of the signal is used to carry the information of the signal. See also A.M.
A.V.C Actuator Valve Controller: a valve controller triggered by an actuator, a device which transforms an input signal (usually an electrical signal) into mechanical motion.
D.C Direct Current: an electric current which flows in one direction only. Other system of electric current transmission is A.C.
A.M Amplitude Modulation: the system of radio transmission whereby the wave is modulated by variation of its amplitude, i.e. the amplitude of the signal is used to carry the information of the signal. See also F.M.
A.F Audio Frequency: a frequency capable of being heard by the human ear, usually 20Hz. to 20kHz.
A.C Alternating Current: an electric current which continually reverses its direction of flow in a regular fashion. The vast majority of electricity supply systems use A.C. The other system of electric current transmission is Direct Current (D.C.).
Wavemeter An electrical device for measuring the wavelength of a radio frequency (R.F.) wave either directly or indirectly, through the determination of the frequency.
Wavelength The distance between successive peaks or maxima of a wave. The wavelength determines the nature of the various forms of radiant energy that comprise the electromagnetic spectrum.
volt The standard unit of potential difference or electromotive force, named after Alessandro Volta. One volt is the potential difference across a conductor when a current of one ampere dissipates one watt of power. The volt is the standard unit of voltage: the force, or pressure, of electricity.
Vernier Scale A small, movable auxiliary graduated scale attached parallel to a main graduated scale, calibrated to indicate fractional parts of the subdivisions of the larger scale, and used on certain precision instruments to increase accuracy in measurement; an auxiliary device designed to facilitate fine adjustments or measurements on precision instruments.
Variometer An inductor whose total inductance can be varied either by altering the relative position of two coaxial coils connected in series or by the use of permeability tuning, and thus can be used to tune a circuit.
Valve Receiver A radio receiver set which employees the use of radio valves or tubes.
Tungsten A hard, brittle, corrosion-resistant, gray to white metallic element commonly used in pure or alloy form in high-temperature structural materials, such as lamp and valve filaments.
Triode A multi-grid radio valve (or tube) with three electrodes (an anode, cathode, and a control grid), commonly used in audio and radio amplifiers, and oscillator circuits.
Trimmer A small adjustable capacitor usually used for the fine adjustment of a larger capacitor to which it is connected.
Trembler Coil A dual-purpose electrical device combining the properties of an early form of spark plug and a circuit-breaker, i.e. an electrical device that produces sparks for starting magnetos, dynamos and general engines and also alternately makes and breaks the circuit in an induction coil.
Transmitter A wireless or radio transmitter; the set that transmits or sends a wireless message or radio broadcast. Early wireless sets usually consisted of separate receivers and transmitters, while later radio communication sets were transceivers â€` combination receivers and transmitters.
Transformer An electrical device that transfers energy from one circuit to another by magnetic coupling with no moving parts. Transformers provide a change in voltage, current, phase or other electric characteristic during the transfer and hence are used to convert between high and low voltages, to change impedance, and to provide electrical isolation between circuits.
Thermionic Valve A basic and early radio valve (or tube) in which electrons are emitted from a heated cathode, some or all of the electrons being collected by an anode, their flow being usually controlled by additional grid-types electrodes; a late 19th century/early 20th century term commonly used in Britain.
Tetrode A multi-grid radio valve (or tube) with four electrodes (an anode, cathode, a control grid, and an additional grid-type electrode), commonly used in high-end audio amplifiers etc.
Terminal In electricity, a position in a circuit or device at which a connection is normally established or broken, or a passive conductor at such a position used to facilitate the connection.
Telegraph Relay An electronic device, commonly used in wired and wireless telegraphy, that receives a weak or low-level signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. In modern terms, a telegraph repeater, or amplifier.
Teak A dark, heavy, oily wood of great strength and durability, usually a distinct rich reddish brown in colour.
Tapper An electromagnetic device used to shake the filings of a coherer after the detection of a wireless signal has caused the filings to cohere and become conducting. Sometimes referred to as a Morse Tapper. See also Coherer.
Syntony The condition of being syntonic, or ‘tuned` so as to respond to one another, as two electric circuits. Early term for ‘tuned` circuits, as developed by Marconi around 1901.
Syntoniser A device, usually consisting of a variable inductance coil and condenser with a pair of adjustable spark balls, for attuning the time periods of antennae in wireless telegraphy. Marconi began experimenting with syntony (or ‘tuning`) in 1901.
Spark Gap Electrical apparatus used for the production of repeated spark discharges between the two or more electrodes forming the system; a transmitting device for generating radio frequency (R.F.) waves, commonly used in early wireless transmitter. Remained in popular usage until the advent of the Multiple Tuner and Magnetic Detector combination around 1908. The first demonstrations of practical radio communication, both by Marconi and others, were carried out using spark gap transmitters.
Socle A plain square block higher than a plinth, serving as a pedestal for sculpture, a vase, or a bust.
Spark Coil More commonly referred to as an Induction Coil.
Side Pip An external seal-off tip upon the side of a radio valve (or tube); colloquial British term.
Shunt Regulator An electrical device that begins conducting at a specified voltage and conducts as much current as required to hold its terminal voltage to that specified voltage. The power supply is designed to only supply a maximum amount of current that is within the safe operating capability of the voltage reference (i.e. the shunt regulating device).
Screened A term used to describe a radio valve (or tube) where the screen grid is arranged so as to give the maximum screening between the anode and the control grid. Commonly used in reference to pentode radio valves (or tubes).
Rotary Spark-Gap A spark-gap consisting of a studded or toothed disc which revolves between two fixed electrodes. When the studs are opposite the fixed electrodes, the spark jumps from one electrode to the disc stud, current passes through the disc and the spark jumps across the second gap to the other fixed electrode.
Rotary Spark Discharger A part of an electronic device that releases stored energy or electric charge from a rotary spark-gap.
Rheostat A continuously variable electrical resistor used to regulate and control current. Usually controlled or varied by mechanical means. Sometimes referred to as a variable resistor.
Reverse The face turned away from the observer; commonly used in reference to coins, medals and art.
Resistor A passive device used to control, or impede the flow of, electric current in an electric circuit by providing resistance, thereby developing a drop in voltage across the device.
Regenerator Unit An electrical unit which amplifies the received signal(s) by means of a controlled amount of positive feedback; a late 19th century/early 20th century term for a transformer unit.
Rectifier An object or device that converts alternating current (A.C.) into direct current (D.C either by the inversion of the suppression of alternate half-waves of the alternating current (A.C.).
Receiver A wireless or radio receiver; the set that receives a wireless message or radio broadcast. Early wireless sets usually consisted of separate receivers and transmitters, while later radio communication sets were transceivers â€` combination receivers and transmitters.
Reactance The opposition to the flow of alternating current (A.C.) caused by the inductance and capacitance in a circuit rather than by resistance. Impedance is a complex combination of reactance and resistance.
Primary Coil A coil to which the input voltage is applied in an inductively coupled circuit, particularly a transformer.
Potentiometer An instrument for measuring an unknown potential difference (voltage) by comparing it to a known standard voltage by passing a known current through a known resistance; works on the principle of a potential divider.
Portable A mechanical device or electrical apparatus manufactured in smaller and lighter form than normal, thereby easier to be carried about. Also, capable of being carried or moved, possibly from one place to another, with ease.
Porcelain A hard, white, translucent ceramic or earthenware, made by firing pure clay and then glazing it with variously coloured fusible materials. Also referred to as china.
Plinth The base block at the intersection of the baseboard and the vertical trim around an opening; the squared base of a piece of furniture.
Plate Radio valve (or tube) component, more commonly referred to as anode (US).
Platinum A metallic silvery-white chemical element with the properties of being hard and relatively inert, and having a very high melting point. Commonly used in jewellery, electrical and laboratory equipment, and industrial catalysts.
Perspex A trademarked polymethyl methacrylate: a tough, transparent thermoplastic acrylic resin that is much lighter than glass and does not splinter.
Pentode A multi-grid radio valve (or tube) with five electrodes (anode, cathode, control grid, screen grid, suppressor grid), commonly used in high-end audio preamplifiers, ham radios and assorted other electronic circuits.
Oscillation Valve An early form of radio valve (or tube) in a basic diode form where the grid and anode are connected through an external circuit so as to produce oscillations; the frequency of the oscillations are determined by the constant of the circuit. Commonly used in conjunction with Fleming`s early experimental valves (c. 1898-1902), as made by Dr J. A. Fleming, scientific advisor to the Marconi Company.
Ohmmeter An instrument for direct measurement of the electrical resistance of a conductor, in the unit of Ohms.
Orb A sphere or spherical object.
ohm The standard unit of electrical impedance or, in the case of direct current (D.C.) electrical resistance, named after Georg Ohm, represented by the symbol ?. One ohm is a resistance that produces a potential difference of one volt when a current of one ampere is flowing through it.
Obverse The face turned towards the observer; commonly used in reference to coins, medals and art.
Nickelled Coated, covered or plated with nickel.
Note Magnifier An Amplifier; term commonly used in the early 1920s, especially in Britain.
Neon Indicator Neon Indicator [Tube]; a cold-cathode tube containing neon and designed to visually determine a potential difference or field.
Multiple Tuner A device used in conjunction with the magnetic detector to produce a practical system that effectively implemented Marconi`s principles of tuning. In conjunction with the Magnetic Detector, the Multiple Tuner was the standard form of spark telegraphic signalling device between 1908 and 1918 in both ship and shore installations until they was gradually superseded by the crystal and later by the valve.
Morse Tape Inker A device for recording the Morse code (i.e. dots and dashes) of the received signal upon paper recording tape. Requires a certain amount of signal power. Used in electrical (wired) telegraphy and early wireless telegraphy.
MHz mega-hertz: one million (1,000,000) hertz, a unit of frequency.
Mica A small glistening particle of talc or other crystalline substance present in large numbers in the structure of a rock; commonly used in ‘crystal` radio sets.
Metal Alloy A mixture of metals; a metallic compound.
mF milli-farads: one-thousandth of a Farad, a unit of capacitance.
Magneto-Electric Machine An electrical device used from the mid 19th century until the early 20th century as a ‘cure` for a wide variety of physical and nervous disorders through electric shock treatment. It was believed to be beneficial to pass electric current through the human body, and these devices could be used in the comfort of the home; an example of ‘quack medicine`.
Magnetic Detector One of the first practical devices able to make radio signals audible through a pair of earphones. Marconi's Magnetic Detector was first patented in 1902; it was an important advance and more sensitive than the coherer. In conjunction with the Multiple Tuner, the Magnetic Detector was the standard form of spark telegraphic signalling device between 1908 and 1918 in both ship and shore installations until they was gradually superseded by the crystal and later by the valve.
Loop Aerial A radio aerial or antenna consisting of one or more loops of wire.
mA milli-ampere: one-thousandth of an ampere, a unit of electric current.
Leyden Jar A device consisting of a glass jar lined inside and out with tinfoil, with a conducting rod connected to the inner foil lining and passing out of the jar through an insulated stopper; used by early experimenters to build and store electric energy. Also referred to as a condenser, as many people thought of electricity as fluid or matter that could be condensed. Referred to in modern terms as a capacitor.
Lend-Lease A program from 1941 to 1945 that allowed the United States to provide the Allied Powers with war material without initially becoming directly involved in the war; officially implemented by the Lend-Lease Act of March 1941.
Leclanche Cell One of the first electrical batteries; more commonly referred to as a carbon cell or dry cell. Developed by Georges Leclanche in 1866, the Leclanche cell remained practically unchanged throughout its long history and was still supplied up to the mid 20th century.
Lead-In A wire that connects an exterior or peripheral component to the main electronic device.
kHz kilo-hertz: one thousand hertz, a unit of frequency.
Lacquer A glossy, resinous, clear or coloured synthetic coating, commonly used as a surface coating.
Jigger Term, commonly used in the late 19th century/early 20th century, to refer to a high-frequency transformer used in early spark transmitters to couple the aerial circuit to the oscillation-generating circuit. In modern terms, a type of transformer.
Japanned Varnished, lacquered, or adorned with japan or in Japanese style.
Interrupter A device that periodically and automatically opens and closes an electric circuit, producing pulses; a device for interrupting an electric current.
Insulator An object or material that, by the property of high resistance, insulates the surround material from usually high voltage electricity. In more general terms, a non-conductor of electricity, sound or heat.
Ink-Writer More commonly referred to as a Morse Tape Inker.
Induction Coil An apparatus for producing electric currents by induction; a passive electrical device used to produce high-voltage pulses from a low-voltage D.C. supply, essentially a transformer. Also referred to as a spark coil.
Inductance The property of an electric circuit or device by which an electromotive force is induced in the circuit itself as the result of opposition to change in magnetic flux, or current flow.
Impedance A measure of the total opposition to the flow of alternating current (A.C.) round a circuit; a complex combination of ohmic resistance and reactance.
Hz See Hertz.
Hertzian Waves Late 19th/early 20th century term for electromagnetic waves; sometimes used to refer to early experimental wireless telegraphy. Named after German physicist Heinrich Hertz (1857-1894), discoverer of electromagnetic radiation and U.H.F. radio waves.
hertz The standard unit of frequency, named after Heinrich Hertz, represented by the symbol Hz. One hertz is an event that repeats (or cycles) once per second, two hertz is an event that repeats (or cycles) twice per second, and so on.
Goniometer More commonly referred to as a direction-finder.
Helical Having the shape of a helix or spiral; screw-shaped.
Glazed Fitted or covered with glass; having a shiny surface or coating.
Gimbal A device, usually consisting of a pair rings mounted on pivots or axes at right angles to each other so that an object will remain suspended in a horizontal plane between them regardless of any motion of its support. Commonly used for sea-faring instruments so as to counteract the motion of the vessel.
GHz giga-hertz: one billion (1,000,000,000) hertz, a unit of frequency.
Gettered In radio valves (or tubes), the action of evacuating an enclosure of gas by the means of a getter, i.e. by chemical or other action. Usually used in reference to the de-gassing of a hard-vacuum valve (or tube).
