Number of glossary terms: 156

Ω:See ohm.

A.:See ampere.

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.).

A.F.:Audio Frequency: a frequency capable of being heard by the human ear, usually 20Hz. to 20kHz.

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.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.

Accumulator:An apparatus for accumulating or increasing the intensity of an electric charge. In modern terms, a capacitor.

Aerial Lead-In:A lead-in from the aerial (or ‘antenna’) to the main device.

Aerial Trimmer:A trimmer for an aerial or ‘antenna’.

Alternator:A synchronous Alternating Current (A.C.) electrical generator or dynamo.

Ammeter:A low-resistance instrument that measures the force of electric current in units of Amperes.

ampere:The standard unit of measure of electric current, named after Andre-Marie Ampere, represented by the symbol A. One ampere is the electric current produced in a circuit by one volt acting through a resistance of one ohm.

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.

Amplitude:The maximum magnitude in displacement of a periodic or oscillating electrical wave; the noise strength of sound waves, in terms of pressure.

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.

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.

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.

B.V.A.:The British Radio Valve Manufacturers’ Association (B.V.A.): a registered trade union established in July 1926. In essence it was a sales agreement, signed by the seven major British valve manufacturers, which secured a uniform practice in the sale of radio valves for broadcasting purposes in the UK. Despite being considered a form of restrictive practice and price fixing, the organisation continued into the 1950s.

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.

Bakelite:A trademarked thermosetting hardened synthetic resin material commonly used for electrical insulators, telephone receivers and assorted industrial manufacturing.

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.

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.

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.

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.

Capacitance:A unit measurement of a system’s ability to store electrical charge.

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.

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.

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.

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.

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.

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.

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’.

Co-axial:Sharing a common axis or core.

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.

Condenser:An apparatus for accumulating or increasing the intensity of an electric charge. Referred to in modern terms as a capacitor.

Contact:The part of an electrical circuit which, when connected, completes the electric circuit and permits the flow of electric current.

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.

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.

D.C.:Direct Current: an electric current which flows in one direction only. Other system of electric current transmission is A.C.

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.

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.

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.

Domestic:Relating to household usage as opposed to commercial usage.

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.

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.

Electrode:A conductor by means of which electricity enters or leaves a medium. Common examples include an anode or cathode.

Element:A radio valve (or tube) component, more commonly referred to as an electrode (US).

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.

F.:See farad.

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.

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.

Filament:A radio valve (or tube) component, more commonly referred to as a cathode (US).

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.).

Galena:A lustrous, blue-gray lead ore mineral, usually crystallised in cubes. Galena crystals were commonly used in ‘crystal’ radio sets.

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.

Generator:A device that produces electricity, particularly one that converts mechanical energy into electrical energy.

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).

GHz.:giga-hertz: one billion (1,000,000,000) hertz, a unit of frequency.

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.

Glazed:Fitted or covered with glass; having a shiny surface or coating.

Goniometer:More commonly referred to as a direction-finder.

H.F.:High Frequency: a radio frequency in the range 3-30MHz. (3,000 kHz. - 30,000kHz.). See also L.F.

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.

Helical:Having the shape of a helix or spiral; screw-shaped.

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.

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.

Hz.:See Hertz.

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.).

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.

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.

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.

Ink-Writer:More commonly referred to as a Morse Tape Inker.

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.

Interrupter:A device that periodically and automatically opens and closes an electric circuit, producing pulses; a device for interrupting an electric current.

Japanned:Varnished, lacquered, or adorned with japan or in Japanese style.

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.

kHz.:kilo-hertz: one thousand hertz, a unit of frequency.

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.

L.W.:Long Wave: A radio wave of greater than 1000 metres and, in modern usage, less than 10,000 metres.

Lacquer:A glossy, resinous, clear or coloured synthetic coating, commonly used as a surface coating.

Lead-In:A wire that connects an exterior or peripheral component to the main electronic device.

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.

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.

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.

Loop Aerial:A radio aerial or antenna consisting of one or more loops of wire.

M.W.:Medium Wave: A radio wave of between 300 and 3,000 kHz.

mA.:milli-ampere: one-thousandth of an ampere, a unit of electric current.

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.

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’.

Metal Alloy:A mixture of metals; a metallic compound.

mF.:milli-farads: one-thousandth of a Farad, a unit of capacitance.

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.

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.

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.

Neon Indicator:Neon Indicator [Tube]; a cold-cathode tube containing neon and designed to visually determine a potential difference or field.

Nickelled:Coated, covered or plated with nickel.

Note Magnifier:An Amplifier; term commonly used in the early 1920s, especially in Britain.

Obverse:The face turned towards the observer; commonly used in reference to coins, medals and art.

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.

Ohmmeter:An instrument for direct measurement of the electrical resistance of a conductor, in the unit of Ohms.

Orb:A sphere or spherical object.

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.

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.

Perspex:A trademarked polymethyl methacrylate: a tough, transparent thermoplastic acrylic resin that is much lighter than glass and does not splinter.

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.

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.

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.

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.

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.

Primary Coil:A coil to which the input voltage is applied in an inductively coupled circuit, particularly a transformer.

R.F.:Radio Frequency: a frequency in the range within which radio waves may be transmitted, from about 3kHz to about 3GHz.

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.

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 - combination receivers and transmitters.

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.).

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.

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.

Reverse:The face turned away from the observer; commonly used in reference to coins, medals and art.

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.

Rotary Spark Discharger:A part of an electronic device that releases stored energy or electric charge from a rotary spark-gap.

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.

S.W.:Short Wave: a radio wavelength of relatively short wavelength, corresponding to between about 2,000kHz. and 25MHz.

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).

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).

Side Pip:An external seal-off tip upon the side of a radio valve (or tube); colloquial British term.

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.

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.

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.

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.

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.

Teak:A dark, heavy, oily wood of great strength and durability, usually a distinct rich reddish brown in colour.

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.

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.

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.

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.

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.

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 - combination receivers and transmitters.

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.

Trimmer:A small adjustable capacitor usually used for the fine adjustment of a larger capacitor to which it is connected.

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.

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.

Valve Receiver:A radio receiver set which employees the use of radio valves or tubes.

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.

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.

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.

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.

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.

Number of glossary terms: 156

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