A telegraphist, telegrapher, or telegraph operator is an operator who uses a telegraph key to send and receive the Morse code in order to communicate by land lines or radio. Telegraphist was one of the first "high-technology" professions of the modern era. Many young men and young women left their farms and fishing communities in the late 19th century to take high-paying jobs as professional telegraph operators. In those early days telegraphers were in such demand that operators could move from place to place and job to job to achieve ever-higher salaries, thereby freeing them from subsistence lives on family farms. During the Great War the Royal Navy enlisted many volunteers as radio telegraphists. Telegraphists were indispensable at sea in the early days of wireless telegraphy, many young men were called to sea as professional radiotelegraph operators who were always accorded high-paying officer status at sea. Subsequent to the Titanic disaster and the Radio Act of 1912, the International Safety of Life at Sea conventions established the 500kHz maritime distress frequency monitoring and mandated that all passenger-carrying ships carry licensed radio telegraph operators.
High-paying jobs as seagoing ship's radiotelegraphy officers were still common until the late 20th century. In the 21st century, the employment of professional radio telegraphers was discontinued in maritime service and replaced by the use of satellite communications services; the use of Morse code is over a century old. Fluent Morse code telegraphers still enjoy sending Morse code using manually operated mechanical keys or electronic keyers. Although Morse code is no longer used in commercial practices, the use of hand-sent Morse code seems to be growing among amateur radio operators though Morse proficiency is no longer required to obtain an amateur radio licence. Using the computer keyboard or hand-operated telegraph key, today all Morse code operators are amateur radio enthusiasts. Amateur radio Casa del Telegrafista, a museum in Colombia Commercial Cable Company List of telegraphists Morse code Prosigns for Morse code telegraph key Transatlantic telegraph cable Sinking of the RMS Titanic
A magnetic field is a vector field that describes the magnetic influence of electric charges in relative motion and magnetized materials. Magnetic fields are observed from subatomic particles to galaxies. In everyday life, the effects of magnetic fields are seen in permanent magnets, which pull on magnetic materials and attract or repel other magnets. Magnetic fields surround and are created by magnetized material and by moving electric charges such as those used in electromagnets. Magnetic fields exert forces on nearby moving electrical torques on nearby magnets. In addition, a magnetic field that varies with location exerts a force on magnetic materials. Both the strength and direction of a magnetic field vary with location; as such, it is an example of a vector field. The term'magnetic field' is used for two distinct but related fields denoted by the symbols B and H. In the International System of Units, H, magnetic field strength, is measured in the SI base units of ampere per meter. B, magnetic flux density, is measured in tesla, equivalent to newton per meter per ampere.
H and B differ in. In a vacuum, B and H are the same aside from units. Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. Magnetic fields and electric fields are interrelated, are both components of the electromagnetic force, one of the four fundamental forces of nature. Magnetic fields are used throughout modern technology in electrical engineering and electromechanics. Rotating magnetic fields are used in both electric generators; the interaction of magnetic fields in electric devices such as transformers is studied in the discipline of magnetic circuits. Magnetic forces give information about the charge carriers in a material through the Hall effect; the Earth produces its own magnetic field, which shields the Earth's ozone layer from the solar wind and is important in navigation using a compass. Although magnets and magnetism were studied much earlier, the research of magnetic fields began in 1269 when French scholar Petrus Peregrinus de Maricourt mapped out the magnetic field on the surface of a spherical magnet using iron needles.
Noting that the resulting field lines crossed at two points he named those points'poles' in analogy to Earth's poles. He clearly articulated the principle that magnets always have both a north and south pole, no matter how finely one slices them. Three centuries William Gilbert of Colchester replicated Petrus Peregrinus' work and was the first to state explicitly that Earth is a magnet. Published in 1600, Gilbert's work, De Magnete, helped to establish magnetism as a science. In 1750, John Michell stated that magnetic poles attract and repel in accordance with an inverse square law. Charles-Augustin de Coulomb experimentally verified this in 1785 and stated explicitly that the north and south poles cannot be separated. Building on this force between poles, Siméon Denis Poisson created the first successful model of the magnetic field, which he presented in 1824. In this model, a magnetic H-field is produced by'magnetic poles' and magnetism is due to small pairs of north/south magnetic poles. Three discoveries in 1820 challenged this foundation of magnetism, though.
Hans Christian Ørsted demonstrated that a current-carrying wire is surrounded by a circular magnetic field. André-Marie Ampère showed that parallel wires with currents attract one another if the currents are in the same direction and repel if they are in opposite directions. Jean-Baptiste Biot and Félix Savart announced empirical results about the forces that a current-carrying long, straight wire exerted on a small magnet, determining that the forces were inversely proportional to the perpendicular distance from the wire to the magnet. Laplace deduced, but did not publish, a law of force based on the differential action of a differential section of the wire, which became known as the Biot–Savart law. Extending these experiments, Ampère published his own successful model of magnetism in 1825. In it, he showed the equivalence of electrical currents to magnets and proposed that magnetism is due to perpetually flowing loops of current instead of the dipoles of magnetic charge in Poisson's model.
This has the additional benefit of explaining. Further, Ampère derived both Ampère's force law describing the force between two currents and Ampère's law, like the Biot–Savart law described the magnetic field generated by a steady current. In this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism. In 1831, Michael Faraday discovered electromagnetic induction when he found that a changing magnetic field generates an encircling electric field, he described this phenomenon in. Franz Ernst Neumann proved that, for a moving conductor in a magnetic field, induction is a consequence of Ampère's force law. In the process, he introduced the magnetic vector potential, shown to be equivalent to the underlying mechanism proposed by Faraday. In 1850, Lord Kelvin known as William Thomson, distinguished between two magnetic fields now denoted H and B; the former applied to the latter to Ampère's model and induction. Further, he derived how H and B relate to each other
A battery is a device consisting of one or more electrochemical cells with external connections provided to power electrical devices such as flashlights and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode; the terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants to lower-energy products, the free-energy difference is delivered to the external circuit as electrical energy; the term "battery" referred to a device composed of multiple cells, however the usage has evolved to include devices composed of a single cell. Primary batteries are discarded. Common examples are the alkaline battery used for flashlights and a multitude of portable electronic devices. Secondary batteries can be discharged and recharged multiple times using an applied electric current.
Examples include the lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics such as laptops and smartphones. Batteries come in many shapes and sizes, from miniature cells used to power hearing aids and wristwatches to small, thin cells used in smartphones, to large lead acid batteries or lithium-ion batteries in vehicles, at the largest extreme, huge battery banks the size of rooms that provide standby or emergency power for telephone exchanges and computer data centers. According to a 2005 estimate, the worldwide battery industry generates US$48 billion in sales each year, with 6% annual growth. Batteries have much lower specific energy than common fuels such as gasoline. In automobiles, this is somewhat offset by the higher efficiency of electric motors in converting chemical energy to mechanical work, compared to combustion engines; the usage of "battery" to describe a group of electrical devices dates to Benjamin Franklin, who in 1748 described multiple Leyden jars by analogy to a battery of cannon.
Italian physicist Alessandro Volta built and described the first electrochemical battery, the voltaic pile, in 1800. This was a stack of copper and zinc plates, separated by brine-soaked paper disks, that could produce a steady current for a considerable length of time. Volta did not understand, he thought that his cells were an inexhaustible source of energy, that the associated corrosion effects at the electrodes were a mere nuisance, rather than an unavoidable consequence of their operation, as Michael Faraday showed in 1834. Although early batteries were of great value for experimental purposes, in practice their voltages fluctuated and they could not provide a large current for a sustained period; the Daniell cell, invented in 1836 by British chemist John Frederic Daniell, was the first practical source of electricity, becoming an industry standard and seeing widespread adoption as a power source for electrical telegraph networks. It consisted of a copper pot filled with a copper sulfate solution, in, immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode.
These wet cells used liquid electrolytes, which were prone to leakage and spillage if not handled correctly. Many used glass jars to hold their components, which made them fragile and dangerous; these characteristics made. Near the end of the nineteenth century, the invention of dry cell batteries, which replaced the liquid electrolyte with a paste, made portable electrical devices practical. Batteries convert chemical energy directly to electrical energy. In many cases, the electrical energy released is the difference in the cohesive or bond energies of the metals, oxides, or molecules undergoing the electrochemical reaction. For instance, energy can be stored in Zn or Li, which are high-energy metals because they are not stabilized by d-electron bonding, unlike transition metals. Batteries are designed such that the energetically favorable redox reaction can occur only if electrons move through the external part of the circuit. A battery consists of some number of voltaic cells; each cell consists of two half-cells connected in series by a conductive electrolyte containing metal cations.
One half-cell includes electrolyte and the negative electrode, the electrode to which anions migrate. Cations are reduced at the cathode; some cells use different electrolytes for each half-cell. Each half-cell has an electromotive force relative to a standard; the net emf of the cell is the difference between the emfs of its half-cells. Thus, if the electrodes have emfs E 1 and E 2 the net emf is E 2 − E 1.
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. Electromagnets consist of wire wound into a coil. A current through the wire creates a magnetic field, concentrated in the hole in the center of the coil; the magnetic field disappears. The wire turns are wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the main advantage of an electromagnet over a permanent magnet is that the magnetic field can be changed by controlling the amount of electric current in the winding. However, unlike a permanent magnet that needs no power, an electromagnet requires a continuous supply of current to maintain the magnetic field. Electromagnets are used as components of other electrical devices, such as motors, electromechanical solenoids, loudspeakers, hard disks, MRI machines, scientific instruments, magnetic separation equipment. Electromagnets are employed in industry for picking up and moving heavy iron objects such as scrap iron and steel.
Danish scientist Hans Christian Ørsted discovered in 1820 that electric currents create magnetic fields. British scientist William Sturgeon invented the electromagnet in 1824, his first electromagnet was a horseshoe-shaped piece of iron, wrapped with about 18 turns of bare copper wire. The iron was varnished to insulate it from the windings; when a current was passed through the coil, the iron became magnetized and attracted other pieces of iron. Sturgeon displayed its power by showing that although it only weighed seven ounces, it could lift nine pounds when the current of a single-cell battery was applied. However, Sturgeon's magnets were weak because the uninsulated wire he used could only be wrapped in a single spaced out layer around the core, limiting the number of turns. Beginning in 1830, US scientist Joseph Henry systematically improved and popularized the electromagnet. By using wire insulated by silk thread, inspired by Schweigger's use of multiple turns of wire to make a galvanometer, he was able to wind multiple layers of wire on cores, creating powerful magnets with thousands of turns of wire, including one that could support 2,063 lb.
The first major use for electromagnets was in telegraph sounders. The magnetic domain theory of how ferromagnetic cores work was first proposed in 1906 by French physicist Pierre-Ernest Weiss, the detailed modern quantum mechanical theory of ferromagnetism was worked out in the 1920s by Werner Heisenberg, Lev Landau, Felix Bloch and others. A portative electromagnet is one designed to just hold material in place. A tractive electromagnet applies a force and moves something. Electromagnets are widely used in electric and electromechanical devices, including: Motors and generators Transformers Relays Electric bells and buzzers Loudspeakers and headphones Actuators such as valves Magnetic recording and data storage equipment: tape recorders, VCRs, hard disks MRI machines Scientific equipment such as mass spectrometers Particle accelerators Magnetic locks Magnetic separation equipment, used for separating magnetic from nonmagnetic material, for example separating ferrous metal from other material in scrap.
Industrial lifting magnets magnetic levitation, used in a maglev train or trains Induction heating for cooking and hyperthermia therapy A common tractive electromagnet is a uniformly-wound solenoid and plunger. The solenoid is a coil of wire, the plunger is made of a material such as soft iron. Applying a current to the solenoid applies a force to the plunger and may make it move; the plunger stops moving. For example, the forces are balanced; the maximum uniform pull happens. An approximation for the force F is F = C A n I / l where C is a proportionality constant, A is the cross-sectional area of the plunger, n is the number of turns in the solenoid, I is the current through the solenoid wire, l is the length of the solenoid. For units using inches, pounds force, amperes with long, solenoids, the value of C is around 0.009 to 0.010 psi. For example, a 12-inch long coil with a long plunger of 1-square inch cross section and 11,200 ampere-turns had a maximum pull of 8.75 pounds. The maximum pull is increased.
The stop becomes a magnet. An approximation for the pull P is P = A n I = + Here la is the distance between
Morse code is a character encoding scheme used in telecommunication that encodes text characters as standardized sequences of two different signal durations called dots and dashes or dits and dahs. Morse code is named for Samuel F. B. Morse, an inventor of the telegraph; the International Morse Code encodes the 26 English letters A through Z, some non-English letters, the Arabic numerals and a small set of punctuation and procedural signals. There is no distinction between lower case letters; each Morse code symbol is formed by a sequence of dashes. The dot duration is the basic unit of time measurement in Morse code transmission; the duration of a dash is three times the duration of a dot. Each dot or dash within a character is followed by period of signal absence, called a space, equal to the dot duration; the letters of a word are separated by a space of duration equal to three dots, the words are separated by a space equal to seven dots. To increase the efficiency of encoding, Morse code was designed so that the length of each symbol is inverse to the frequency of occurrence in text of the English language character that it represents.
Thus the most common letter in English, the letter "E", has the shortest code: a single dot. Because the Morse code elements are specified by proportion rather than specific time durations, the code is transmitted at the highest rate that the receiver is capable of decoding; the Morse code transmission rate is specified in groups per minute referred to as words per minute. Morse code is transmitted by on-off keying of an information carrying medium such as electric current, radio waves, visible light or sound waves; the current or wave is present during time period of the dot or dash and absent during the time between dots and dashes. Morse code can be memorized, Morse code signalling in a form perceptible to the human senses, such as sound waves or visible light, can be directly interpreted by persons trained in the skill; because many non-English natural languages use other than the 26 Roman letters, Morse alphabets have been developed for those languages. In an emergency, Morse code can be generated by improvised methods such as turning a light on and off, tapping on an object or sounding a horn or whistle, making it one of the simplest and most versatile methods of telecommunication.
The most common distress signal is SOS – three dots, three dashes, three dots – internationally recognized by treaty. Early in the nineteenth century, European experimenters made progress with electrical signaling systems, using a variety of techniques including static electricity and electricity from Voltaic piles producing electrochemical and electromagnetic changes; these numerous ingenious experimental designs were precursors to practical telegraphic applications. Following the discovery of electromagnetism by Hans Christian Ørsted in 1820 and the invention of the electromagnet by William Sturgeon in 1824, there were developments in electromagnetic telegraphy in Europe and America. Pulses of electric current were sent along wires to control an electromagnet in the receiving instrument. Many of the earliest telegraph systems used a single-needle system which gave a simple and robust instrument. However, it was slow, as the receiving operator had to alternate between looking at the needle and writing down the message.
In Morse code, a deflection of the needle to the left corresponded to a dot and a deflection to the right to a dash. By making the two clicks sound different with one ivory and one metal stop, the single needle device became an audible instrument, which led in turn to the Double Plate Sounder System; the American artist Samuel F. B. Morse, the American physicist Joseph Henry, Alfred Vail developed an electrical telegraph system, it needed a method to transmit natural language using only electrical pulses and the silence between them. Around 1837, therefore, developed an early forerunner to the modern International Morse code. William Cooke and Charles Wheatstone in England developed an electrical telegraph that used electromagnets in its receivers, they obtained an English patent in June 1837 and demonstrated it on the London and Birmingham Railway, making it the first commercial telegraph. Carl Friedrich Gauss and Wilhelm Eduard Weber as well as Carl August von Steinheil used codes with varying word lengths for their telegraphs.
In 1841, Cooke and Wheatstone built a telegraph that printed the letters from a wheel of typefaces struck by a hammer. The Morse system for telegraphy, first used in about 1844, was designed to make indentations on a paper tape when electric currents were received. Morse's original telegraph receiver used a mechanical clockwork to move a paper tape; when an electrical current was received, an electromagnet engaged an armature that pushed a stylus onto the moving paper tape, making an indentation on the tape. When the current was interrupted, a spring retracted the stylus and that portion of the moving tape remained unmarked. Morse code was developed so that operators could translate the indentations marked on the paper tape into text messages. In his earliest code, Morse had planned to transmit only numerals and to use a codebook to look up each word according to the number, sent. However, the code was soon expanded by Alfred Vail in 1840 to include letters and special characters so it could be used more generally.
Vail estimated the frequency of use of letters in the English language by counting the movable type he found in the type-cases of a local newspaper in Morristown. The shorter marks were called "dots" and the longer ones "dashes", the letters most used were assigned the shorter sequences of dots and dashes; this code was used since 1844 and became known as Morse lan
A relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are used, such as solid-state relays. Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuits must be controlled by one signal; the first relays were used in long distance telegraph circuits as amplifiers: they repeated the signal coming in from one circuit and re-transmitted it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations. A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults.
Magnetic latching relays require one pulse of coil power to move their contacts in one direction, another, redirected pulse to move them back. Repeated pulses from the same input have no effect. Magnetic latching relays are useful in applications where interrupted power should not affect the circuits that the relay is controlling. Magnetic latching relays can have either dual coils. On a single coil device, the relay will operate in one direction when power is applied with one polarity, will reset when the polarity is reversed. On a dual coil device, when polarized voltage is applied to the reset coil the contacts will transition. AC controlled magnetic latch relays have single coils that employ steering diodes to differentiate between operate and reset commands, it was used in long distance telegraph circuits, repeating the signal coming in from one circuit and re-transmitting it to another. In 1809 Samuel Thomas von Sömmerring designed an electrolytic relay as part of his electrochemical telegraph.
American scientist Joseph Henry is claimed to have invented a relay in 1835 in order to improve his version of the electrical telegraph, developed earlier in 1831. It is claimed that English inventor Edward Davy "certainly invented the electric relay" in his electric telegraph c.1835. A simple device, now called a relay, was included in the original 1840 telegraph patent of Samuel Morse; the mechanism described acted as a digital amplifier, repeating the telegraph signal, thus allowing signals to be propagated as far as desired. The word relay appears in the context of electromagnetic operations from 1860. A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, one or more sets of contacts; the armature is mechanically linked to one or more sets of moving contacts. The armature is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit.
In this condition, one of the two sets of contacts in the relay pictured is closed, the other set is open. Other relays may have fewer sets of contacts depending on their function; the relay in the picture has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, the circuit track on the printed circuit board via the yoke, soldered to the PCB; when an electric current is passed through the coil it generates a magnetic field that activates the armature, the consequent movement of the movable contact either makes or breaks a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized the movement opens the contacts and breaks the connection, vice versa if the contacts were open; when the current to the coil is switched off, the armature is returned by a force half as strong as the magnetic force, to its relaxed position. This force is provided by a spring, but gravity is used in industrial motor starters.
Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; when the coil is energized with direct current, a diode is placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Such diodes were not used before the application of transistors as relay drivers, but soon became ubiquitous as early germanium transistors were destroyed by this surge; some automotive relays include a diode inside the relay case. If the relay is driving a large, or a reactive load, there may be a similar problem of surge currents around the relay output contacts. In this case a snubber circuit across the contacts may absorb the surge. Suitably rated capacitors and the associated resistor are sold as a single packaged component for this commonplace use. If the coil is designed to be energized with alternating current, some method is used to split the flux into two out-of-phase components which add together, increasing the minimum pull on the armature during the AC cycle.
This is done with a small copper "shading ring" crimped around a portion of the core that creates the delayed, out-of-phase component, which holds the contacts during the zero crossings of the control voltage. Contact materials for relays vary by application. Mate