TELEGRAPHY

the two outstanding features in the art of telegraphy since 1910 have been (1) the widening ap- plication of printing telegraph systems, particularly those using the baudot or five-unit code, and (2) development of carrier telegraph systems. it has been found feasible to transmit alternating currents of frequencies as high as 30,000 cycles per sec. over open wire metallic return telephone circuits, and by means of thermionic valves or vacuum tubes to amplify the feeble received currents and retransmit or relay them into connecting circuits. as the voice range in ordinary telephone transmission requires only a band width of 2,000 or 3,000 cycles at the low end of this range, the remainder may be used for carrier telegraph and carrier tele- phone (see telephony). a circuit from which telephone and direct current telegraph channels are derived, the telegraph employing the frequency range between zero and the lowest frequencies required for tele- phone purposes, is termed a composited circuit. the separation telegraphy is effected by means of simple electrical filters which are gen- erally referred toasa ‘‘ composite set.”’ the compositing idea has been carried still further by superposing a high frequency carricr telegraph system upon a telephone circuit, the two being sepa- rated as before by more elaborate filters, which are sometimes referred to as a “ high frequency composite set.’’ a carrier telegraph circuit provided with equipment for utilising the al- ternating currents within the voice range for telegraph purposes is termed a “‘ voice frequency carrier telegraph circuit.” amiethods of transmission composite telegraph and telephone.—considerable advance has been made in the technical knowledge of simultaneous tele- graph and telephone operation over the same’ wires. the funda- mental idea was that of van rysselberghe of belgium. by means of electric wave filters, consisting of condensers and inductance coils, a line circuit is bifurcated at the terminals into two circuits, one offering low impedance and attenuation to the low frequency telegraph signals and high impedance and attenuation to the higher frequency telephone currents, the other offering high im- pedance and attenuation to the low frequency telegraph signals and low impedance and attenuation to the higher frequency telephone currents. the telegraph may be operated as a two- wire metallic return circuit, or as two separate grounded circuits. the former is the method used on small gauge circuits in cables, whereas the latter is the standard practice for open wire lines. fig. 1 shows the separating filters or, as they are termed, the c= = a oa oe ee oe oe aa | fo rete- { phone t ~—e we eee ee ee ee it telegraph i set not to tele composite set mis oe, a a, ee ee — eo oe oe fic, 1.—schematic of composite set for grounded telegraph system. ““ composite set. ’’ where it is desired to use two telephone cir- cuits in tandem to provide long telegraph circuits, the telephone circuits are connected together through intermediate composite sets which permit the telegraph currents to pass but effectively separate the circuits for telephone communication. carrier telegraph systems.—the greatest contribution to the art of telegraph transmission over land lines since 1910 has been the application of vacuum tubes and the electrical filter which have made practicable the carrier current systems. two carricr systems have been developed, one the high frequency system for use on open wire lines over which it is possible to transmit alter- nating currents of frequencies above the voice range, and another system for use over land cable circuits, which utilises the voice range of frequencies and so is called the voice frequency system. high frequency carrier telegraph system—the high fre- quency system has been designed for operation over one pair of wires. ‘transmission in both directions is obtained by dividing the band of frequencies available (3,000 to 10,000) at about 6,000 cycles, and using one portion of the band for east to west transmis- sion and the other portion for west to east. this separation is achieved by suitably designed electrical filters termed “ direc- tional filters.””’ to obtain a number of telegraph channels, it is necessary to split up these wide bands— 3,000 to 6,000 and 6,000 741 to 10,000—into narrower bands, but still of sufficient width to enable telegraph signals of good quality to be transmitted. within the frequency range mentioned, 10 telegraph channels in each direction are obtained. an east to west channel is associated with a west to east channel, thereby providing the equivalent of a duplex circuit. a carrier system thus provides the equivalent of 1o duplex circuits. each channel of a high frequency carricr system comprises a vacuum tube oscillator, tuned to a particular frequency, the steady output from which is applied intermittently by the actua- tion of the sending key or other transmitting device used. these trains of alternating current waves are amplified, pass through a tuned selective circuit, combine with the signals from other channels and thence flow into the line. at the receiving end they enter aselective circuit which, being tuned to the same frequency, offers a path of low impedance to them but a hizh impedance to all other frequencics. the signals are then amplified and recti- fied, the rectified signals actuating a relay. to separate the car- rier currents as a group from the currents used for ordinary teleph- ony and telegraphy, “‘ high pass” and “ low pass ”’ filters are used. this combination of filters is sometimes called a high fre- quency composite set. to separate the voice frequency currents from the currents of still lower frequencies used for the ordinary telegraph circuits, the ordinary composite set is used. carrier circuits of this type provide hizh grade signals, are very stable in operation and are free from the balance troubles of direct current duplex systems. this system has enabled the fol- lowing communication facilities to be obtained commercially from a single pair of open wires: 20 one-way carricr telegraph channels, 4 one-way direct current telegraph channels, and 14 telephone circuits including the phantom. voice frequency currier telegraph system—the heavy tele- phone traffic in thickly populated territories has led to the use of cable circuits in place of open wire lines. to provide telegraph facilities over such routes, it would not be possible to use the high frequency carrier system because of the great attenuation of high frequency currents in cable conductors. the need for such facilities led to the development of a carrier system using frequencies within the voice range. this system has been de- signed particularly for use over four-wire telephone circuits so that the same frequencies may be used in each direction. al- though fundamentally the same principle as the high frequency system, this system differs in a number of details. one multi- frequency generator, furnishing currents of 12 frequencies from 425 to 2,295 cycles per sec., spaced 170 cycles apart, is the source of power, and is capable of feeding as many as 20 sepa- rate carrier systems, #.¢., 240 carrier channels. the steadily ap- plied carrier current of each channel is interrupted by actuation of the transmitting key or other sending device. this interrupted carrier current passes through a sending band filter constructed as to permit relatively free passage of current of frequencies slightly above and below the carrier frequency for which it was designed. to currents of other frequencies it offers a high impedance, and this practically excludes them. after passing through the filter, the current combines with currents of other frequencies from the other channels and passes over the line as a composite current. as the over-all range of frequencies and the energy levels are about the same as those of telephone circuits, standard telephone repeaters are used to relay the cur- rents. at the receiving end, the carrier currents are separated by a group of recciving band filters, each of which offers a low imped- ance path to a relatively narrow band of frequencies com- prehending that of a particular carrier frequency and acts substantially as an open circuit to other frequencies. after passing through the receiving filter, the current is amplified and then rectified, the rectified or direct current signals actuating a relay. an east to west channel and a west to east channel are combined to furnish the equivalent of a duplex circuit. the above description applies particularly to a system devel- oped in the united states. in germany a somewhat similar sys- tem has been developed. the german system uses a separate vacuum tube oscillator for each channel and interrupts the 742 carrier currents to form telegraph signals, no sending filters being used. at the receiving end, four-electrode vacuum tubes are used for amplifying and rectifying the signals. over a four-wire circuit, six telegraph channels in each direction are provided. | direct current metallic telegraph system—the increase in knowledge of the fundamental requirements of simultaneous telephone and telegraph operation has enabled a direct current telegraph system to be developed for operation over long small- gauge telephone cable circuits. this system is arranged for me- tallic circuit working using a relay operating with a current of to telephone mrp line fig, 2.—schematic of composite set for metallic return telegraph system, approximately two milliamperes. the general circuit arrange- ments of this system are shown in fig. 2. the cable circuit is di- vided by a composite set or filter into two branches, as has been described under composite telegraphs. all metallic circuits in a single office are supplied from a common battery. the type of sensitive polar relay, which was specially designed for this service, is shown in fig. 3. the relay is provided with four accu- rately balanced line windings and two additional windings for use permanent fic. 3.—polar relay for metallic return cable system. in a gulstad vibrating local circuit. the armature is a reed, fixed at one end, and forms the cross piece of a magnetic bridge. the six windings surround the armature. current in one direction causes that end of the armature carrying the contacts to move towards one pole, and current in the opposite direction causes it to reverse its motion. printing systems creed system.—this system, which came into use early in the present century, has been improved by simplification of appara- tus units and elimination of need for air pressure. the new ma- telegraphy chines are actuated electrically and are capable of operating at much higher speeds than the earlier models. baudot.—use of the baudot multiplex printer system has been widely extended in great britain, and the system modified by british engineers. it has been duplexed, thereby doubling its traffic carrying capacity. transmission is controlled by perfora- ted tapes actuating automatic transmitters, instead of by direct keyboard operation, thereby permitting the rate of operation to be increased about 50%. electrical vibrating reeds and phonic wheel motors are used to drive the distributors, ensuring stable synchronism. | murray multiplex —this system of multiplex is based on the baudot. operators prepare messages by perforating paper tapes by means of keyboard perforating machines having a keyboard similar toa typewriter. each key of the machine, when depressed, perforates a particular combination of holes in accordance with feed holes naw no =m fic. 4.—murray multiplex ‘tape, showing perforations for word “ telegraph." the arrangement of the five-unit code adopted by murray. fig. 4 shows a portion of tape perforated to transmit the word “ tele- graph.”” from the perforating machine the tape passes directly into an automatic transmitter which has five selecting pins, each controlling a contact lever resting normally against a busbar connected to the spacing pole of the line battery. when a select- ing pin passes into a hole in the tape, the associated contact lever moves over and makes contact with a busbar connected to the marking pole of the battery. the positions of the contact levers are therefore determined by the perforations in the tape. each lever is connected to its own particular segment on the sending ring of the distributor, the five segments associated with a trans- mitter usually being placed in sequence around the ring, so that as the brushes pass over the segments a particular combination of signals representing a letter, comprising positive and negative impulses, is sent out to line. immediately the brushes have passed over the last of the segments associated with a particular transmitter, a local current impulse is sent from another ring of the distributor through a “‘ cadence ” electromagnet in the trans- mitter, which when operated withdraws the selecting pins, feeds forward the paper tape and sets up the next letter combination. provision is made to prevent the transmitter overtaking the per- forating operator by causing a taut tape between the two ma- chines to move a light lever and so open the circuit of the “cadence electromagnet,” thereby stopping the operation of the transmitter. as soon as the tape slackens the lever is restored to normal and the transmitter starts again. american multiplex systems——the western electric and western union telegraph companies jointly developed a multi- plex printer system primarily to meet the needs of the western union telegraph company. it resembles the murray system as regards use of keyboard perforators, rotating distributors and page printers, but differs from the murray in many details. in- stead of transmitting extra siznals per revolution of the distribu- tors to maintain synchronism, correcting impulses are generated from the character signals, thus saving line time. a large vibrat- ing fork is used to drive a phonic wheel motor, which is the mo- tive power for the distributor. various types of printer units have been successfully used with this system. all circuits are operated duplex, and double, triple and quadruple channel sys- tems are in service. speeds as high as 50 and 60 words per min. per channel are maintained by operators. another american multiplex printer system has been developed by the morkrum- kleinschmidt company. this system does not differ radically from that described above except for the utilisation of cam- controlled contacts in place of segmented ring distributors with rotating contact brushes. telegraphy stemens and halske automatic system.—this system is a sin- gle channel high speed synchronous printer system, using a five- unit code. at the sending end the operations are practically identical with those of the wheatstone, creed and murray auto- matic. a number of operators prepare perforated tapes which are passed to an operator who feeds them into the transmitter. the hole combinations are arranged across the tape as in the murray multiplex, but the tape has two rows of feed holes, one along each edge. the tape is not stepped forward but moves uni- formly, the transmitter being geared to the distributor brushes. no special signals are transmitted to maintain synchronism, correcting impulses being derived from the message signals. when no messages are being sent, provision is made for sending a signal once per revolution to maintain synchronism. the send- ing distributor brush arm is driven by a shunt wound motor, having a heavy flywheel mounted on the same shaft. the receiving and translating arrangements of the receiver are almost entirely electrical. the brush arm of the receiving ring is mounted on the same shaft as the typewheel. the exact position of the typewheel when the paper tape is momentarily pressed against it to print a letter is determined by the particular signal combination set up in one or other of two groups of storing relays. synchronism is maintained by varying a resistance in the field of the driving motor of the distributor. the printed tape is pasted on message forms, as is the practice with all tape printing ma- chines. provision is made for receiving messages as perforated tapes by associating one of the keyboard perforators with the receiving ring segments. the system may be worked simplex or duplex, and is capable of operating at a maximum speed of 1,000 letters per min. in each direction, i.c., 166 words in the english language. start-stop printer system—a ‘“‘start-stop ” system is one which provides for the transmission of one message over a cir- cuit, or, when duplexed, one message in each direction simulta- neously. the term “start-stop” has been adopted because the dis- tributor brush or equivalent rotating mechanism is started and stopped once per revolution. start-stop sets are in wide use in the united states, where several types have been designed. one type comprises a keyboard transmitter, a motor-driven brush distributor and a printer. in some cases the keyboard is arranged to control a perforator, so that messages may be transmitted either direct from the keyboard, or set up as perforations in a tape and so control the operations of an automatic transmitter. the distributor brush arms (one on each face of the distribu- tor), driven through a friction clutch, are normally held station- ary by a latch and make one rotaticn for each character trans- mitted or received. the start impulse releases the sending start-latch and actuates a relay at the distant station to release the receiving start-latch, so that if the rotation speeds are ap- proximately the same the transmitted impulses are distributed properly to the selecting magnets or clements of the printer at the receiving station. in duplex operation, the sending brush arm and recciving brush arm rotate independently of each other. close synchronism is not required, since the distributors are stopped and caused to start from the same initial position for each character. this feature automatically takes care of line lag and renders the system well adapted for use on circuits having a number of stations operating simultaneously. these systems have been used to a considerable extent over telegraph circuits obtained from telephone circuits and have a maximum speed of about 360 letters or characters per minute. another type of set has a battery of cams mounted within the printer to take the place of the brushes and segmented rings of the distributor. either a page printer capable of operating at 360 letters per min. or a tape printer at about 270 letters per min. may be associated with this set. cipher printing system.—a printing system for rapidly en- ciphering and deciphering telegraph messages has been developed by the engineers of the american telephone and telegraph company. it was successfully applied by the u.s. army signal corps during the world war, when enciphering and deciphering were performed with increased speed and accuracy. 743 gulstad relay.—in 1898 gulstad of copenhagen invented a modified form of polarised relay known as a vibrating relay, the use of which has enabled much higher speeds of working to be attained on all types of telegraph circuits using polar or double current transmission. the principle of the relay may be under- stood by referring to fig. 5. it will be seen that the ends of the local windings are joined to terminals b and c and their centre to terminal a, which is connected through an adjustable resist- ance y to the relay tongue. this resistance is for regulating the local current so that the magnetic effect produced thereby is less than that produced by the steady line current through the line windings. terminal b is connected to ground through a con- denser k and terminal c through a resistance x. generally, resistances x and y are made equal. line coils local coils lo c..0ocuk ‘i koo . fic. §.—schematic of connections for gulstad relay. assuming that there is no current in the line windings and the relay tongue has just reached the contact m (marking), there will then be a momentary rush of current through the winding ab to charge the condenser k, in a direction to keep the tongue to the marking side, thus preventing any tendency of the tongue to rebound. this charging current quickly ceases as the conden- ser becomes charged and directly its intensity falls below that of the current flowing through the winding ac, the preponderance of the latter causes the tongue to move toward the spacing con- tact s. immediately the tongue leaves the marking contact, the condenser k discharges through both windings ba and ac in such a direction as to accelerate the movement of the tongue, so that its transit time from one contact to the other is thereby lessened. when the tongue reaches the opposite contact, the condenser k is again charged, but this time from the other pole of the bat- tery; a similar cycle of effects therefore takes place on that side, and the tongue moves in the reverse direction. in this manner the relay tongue is kept vibrating at 2 speed depending on the values given to the condenser and resistances and the distance of travel of the tongue between its contacts. in practice, the adjustments are such that the rate of vibration of the tongue under the control of the local current is approximately equal to the rate at which the transmitter at the distant station sends re- versals at working speed. when this obtains, the signals passing through the line windings merely determine the length of time that the tongue remains in contact with either stop, its move- ment therefrom being effected by the local current through the local windings as soon as the strength of the line current falls below that of the local current in the winding ac. interference—ground return telegraph circuits are subject to three sources of interference which impair or degrade them, 744 “namely, induction from ac power lines, induction from other telegraph circuits along the same route and differences of direct current earth potential between the terminal stations. in the first case, where the frequency is not too close to that of the tele- graph, the interference can be considerably reduced by the pro- vision of tuned drainage shunts, high impedance anti-resonant series devices and by reducing the responsiveness of the receiving circuits to the interfering current by balancing arrangements. where possible, it is usually preferable, however, to locate and eliminate the source of the induction. this is particularly true in the case of high-speed telegraphs, where the above methods are generally inapplicable. in the second case, the interference is usually mutual between several conductors and is more gen- erally experienced on cable circuits. this interference can be greatly diminished by coupling the duplex scts together by means of condensers and transformers so as to neutralise the current introduced through coupling between the lines. the effect of local ground potential differences can be overcome by supplying a counter electromotive force from a special generator automatically adjusted for neutralisation. statistics the following table gives the miles of telegraph wire throughout the world, jan. 1 1924 and 1910. single wire jan. 1 1924 jan. i 1910 great britain and north ireland 299,307? 311,942? denmark : ; ; 9,352 8,048 france 495,000! 379,888 germany ; : 484,514 388,412 italy . : : : : : : 255,000! 126,505 norway 20,138 13,120 sweden 51,967 40,171 switzerland ; . ; 25,318 16,336 other countries in europe 936,416 826,73 total europe . 2,577,012 2,111,152 british india 347,295 china . 87,000! a japan . we : 162,397 97,300 other countries in asia 175,487 399,030! total asia 772,179 496,330 egypt . ; ; ; 23,067 a union of south africa 44,912 46,853 other countries in africa . 118,618 110,000! total africa 86,597 156,853 united states 1,875,000 1,480,000 canada 270;782 153,000 mexico ‘ : d ‘ ; : 76,105 et other countries in north america . 48,345 78,000 total north amcrica 2,270,232 1,711,000 argentina 175,875 brazil . 95,463 chile ‘ : ; : 38,090 other countries in south america . 59,759 total south america 360, 187 143,590 australia. 97,438 92,909 new zealand 23,067 20,188 philippine islands 9,200 be other places in oceania 21,678 14,700 total oceania 151,383 127,797 total world 6,317,590 4:740;7922 1 partly estimated. ? for great britain, exclusive of [reland. _ bribliography.—k. gulstad, “ vibrating cable relay,” electrical review (june 1898, aug. 1902); a. c. booth, a method of reduc- ing inductive interference,’’ post office electrical iengineers' journal, vol. 2 (1909); d. murray, ‘' practical aspects of printing teleg- raphy,” jour. inst. elec, eng. (1911); d. mcnicol, -lmerican tele- graph practice (1913); ‘‘ the siemens automatic fast speed print- ing telegraph,” electrician (july 11 1913); e. lack, “ the creed telegraphy, submarine telegraph system,” post office flee. eng. jour., vol. 6 (1914); “the gulstad relay,” ibid., vol. 7 (1915), vol. 10 (1918); p. m. rainey, ‘a new printing telegraph system,” electrical world (april 3 1915); a. i. roberts, ‘' a new type printing telegraph system,” post office elec. eng. jour., vol. 8 (1915); report by joint committee on inductive interference (san francisco, sept. 1915); t. e. werbert, telegraphy, 3rd ed. (1916): b. gherardi and f. b. jewett, “ telephone kepeaters,” proc. aner. inst. elec. eng. (oct. igi9); j. u1. bell, “ printing telegraph systems,” 7rans. amer. dnst. lee. iing., vol. 39, pt. 1 (1920); a.c. booth, ‘' telegraph key- board perforators,” post office elec, fug. jour. (july 1921); e. h. colpitts and o. b. blackwell, ‘ carrier current telephony and telegraphy,” amer. inst. elec. eng. jour. (april, may and june 1921); lk. lack, “ description of new creed apparatus,” electrician (jan. 21 1921); j. lh. bell, ‘‘ composite telegraphy and telephony,” post office elec. eng. jour. (april 1922); w. h. martin, g. a. anderegg and b. w. kendall, ‘ key west-havana telephone cable,” amer. inst. elec. eng. jour. (march 1922); a. eh. reiber, printing telegraph systems,” zbid. (feb. 1922); a. e. stone and e. a. lackey, “‘ baudot distributor,” post office elec. eng. jour. (april 1922); h. h. harrison, printing telegraph systems and mechanisms (1923); j. h. bell, r. b. shanck and d. e. branson, ““ metallic polar duplex telegraph system,” amer. inst. elec. eng. jour. (april 1925); s. c. bartholomew, “ power circuit interference, with telegraphs and telephones,” inst. elec, eng. jour. (oct. 1926); j. r. fry and l. a. gardner, ‘‘ polarized telegraph relays,” amer. inst. elec. eng. jour. (march 1925); w. d. hamilton, ‘' a voice frequency telegraph system,” post office flec. eng. jour. (oct. 1925); g. s. vernam, ‘ cipher printing telegraph systems,” a mer. inst. elec. eng. jour. (feb. 1926). cl... ba telegraphy, submarine (sce 26.527).—improved methods of working have been introduced and apparatus has been in- vented with the object of increasing speed and reducing error in transmission and reception. signalling difficulties —one of the factors which limit the spced of signalling over a submarine cable of any considerable length is its inductive capacity due to which the impulses forming the letters, which are transmitted into the cable lose their definition and appear at the receiving end distorted and attenuated in what might be described as a spread out condition. the maxi- mum speed of signalling is therefore that at which it is possible to distinguish between the various impulses or sets of impulses in order to make the signals readable. the siphon recorder is still the instrument generally employed for recording these signals, but whereas in the past the messages were written up by hand, the recorder is now usually employed for watching the shaping of the signals and for adjustment pur- poses, the signals actuating a train of automatic apparatus by which the messages are typed or printed. by the introduction of appropriate capacity and inductance into the sendirg and re- ceiving circuits it is possible to improve greatly the received signals which although reduced in size are much more clearly defined, thus allowing an increase in the speed of transmission. magnifiers—by the use of a magnifier the received signals can be increased in size and, in turn, the speed of transmission may again be raised. magnifiers can seldom be employed to their full advantage on account of imperfections in the duplex balance and local disturbances due to induction from other cir- cuits and electric tramways or powcr mains, but their introduc- tion usually permits an increase of speed of about 30%. in order to minimise the disturbances compensating devices are employed necessitating the use of twins or tricore shore-end cables, the actual point of earthing the circuit usually being some miles out at sea. several forms of magnifier are employed which depend on the movement of a suspended coil as in the case of the siphon recorder, but the movement 3s utilised to bring about the operations described hereafter instead of deflecting the glass tube. an ordinary siphon recorder is usually employed in conjunction with the magnifier to register the resulting signals. the heuriley magnifer—this operates by upsetting the equilibrium of a wheatstone bridge balance, two arms of which are composed of extremely fine wires. the wires carry current and, in the earlier form of the apparatus, are moved by the action of the coil so that they become immersed in or shielded from a current of air. the resulting change in temperature causes an alteration in their resistance values and thus affects the recording instrument connected in the cross circuit of the bridge. in a telegraphy, submarine later form a pair of hot wires carrying current are moved towards or away from a similar but fixed pair thus varying their tem- perature and in consequence, their resistance. the judd and fraser magnificry —this instrument depends on the movement of an electrode between two fixed ones immersed in an electrolyte such as dilute sulphuric acid. the resistances of the electrolyte between the moving and fixed electrodes form two arms of a wheatstone bridge the remaining arms being adjust- able resistances. thus, any displacement of the movable electrode from its symmetrical position between the fixed ones consequent upon deflection of the suspended coil has the effect of upsetting the balance, thereby causing a current to flow through the coil of the recording instrument which is connected in the cross circuit of the bridge. in order to avoid the production of gas and a polarising of the electrodes the current which is passed through the electrolyte is an alternating one. this is brought about by the use of an electrically driven reed carrying a contact head so designed that the positive and negative poles of the battery are rapidly reversed. simultaneously the current in the recording instrument is rectified by means of a second set of contacts mounted on the same reed. a blocking condenser is included in the circuit to prevent the passage of any direct current through the electrolyte. in a later form a three-electrode valve and transformer are introduced to amplify further the current before rectification. the cox magnifier.—in this type a specially constructed sele- nium cell is divided into two sections which form two of the arms of a wheatstone bridge. a beam of light is passed through a metal comb and reflected on to the cell by a small mirror mounted on the suspended coil. a deflection of the coil causes one portion of the cell to become darkened and the other to be- come increasingly illuminated thus bringing about a change in the resistance values of the two sections of the cell and operating the recording instrument or relay in the cross circuit. the orling magnifter —a jet of liquid, such as acidulated water, is deflected by a fine wire attached to the suspended coil, which wire intersects or penetrates the stream. a slight movement of the coil and wire will cause a considerable deflection of the stream which may complete a recorder circuit by coming into contact with one or other of the two conductors situated one on each side of the initial and normal position of the axis of the stream. alternatively, the stream when deflected may provide a temporary bridge between one or the other of the two pairs of contacts. thermionic valves.—these have also been used very success- fully in connection with cable circuits for amplifying purposes. relays (repeaters) —if, instead of tracing the signals by means of a glass tube as in the case of the siphon recorder, the moving coil be employed to make electrical contacts, retransmitting apparatus taking current from a local battery may be operated, thus repeating the weak incoming impulses into a second cable as strong signals. an instrument of this description is known as a relay and on a long cable such an instrument may be used in conjunction with a magnifier. the speed at which a cable may be worked depends very largely on its kr, this being the product of its inductive capacity (k) expressed in farads and its ohmic re- sistance (r). it is, however, dependent to a certain extent on the voltage employed for transmitting, an increase giving a somewhat higher speed. it is usual to consider that the speed at which cables may be worked varies inversely as their krs and if, there- fore, a cable, say, 3,000 m. in length and having a kr of 6 could be diverted into an island situated half way along, the kr of each section would then be 1-5 since both the resistance and capacity values are reduced by one-half. the through speed of working could then be increased four times if an automatic relay were installed at the intermediate station. relays by dr. muirhead and s. g. brown are in considerable use and the “ jockey ” relay introduced by the eastern associated telegraph companies is now almost exclusively employed in their service. this relay permits of the use of ordinary shaping conditions and does not, as in other cases, necessitate the use of an unshunted receiving condenser in the coil circuit in order to 745 block out earth currents which would otherwise involve a dis- turbance of the zero position of the coil thus causing bias or thickening of the signals on one side and thinning on the other. when an unshunted condenser is employed to obviate this trouble a “local correction ” is necessary to counteract the overcurbing or falling away of the received signals consequent upon the use of the condenser. this is usually applied by means of a second winding on the suspended coil, the current through which is adjusted to vary at the correct rate and strength to hold up the signals. with the “ jockey ” relay a correction of this sort is unnecessary since by the use of a resistance shunt over the receiving condenser the overcurbing or falling away of the signals is obviated. the relay contacts are mounted on a frame suspended on a pivot and free to move as the contact tongue attached to the main coil is deflected by the earth current. the frame or “‘ jockey ” carrying the contacts is so damped by means of vanes immersed in oil that it is not displaced under ordinary signalling impulses but is nevertheless able to respond to the relatively slow changes of coil zero brought about by earth cur- rent variations, thus keeping the contacts symmetrically dis- posed with regard to the contact tongue operated by the coil. bruce relay—in a relay introduced by w. m. bruce, a con- tact tongue attached to the suspended coil rests on a revolving drum divided into three insulated contact sections as in the case of s. g. brown’s relay. each of the two outer sections with which the tongue makes contact when the coil is deflected to one side or the other, 1s connected to the grid of a three-electrode valve in the anode circuit of which the windings of a translating device or relay are included. since it is only necessary to transmit po- tential to the grids in order to allow of the passage of anode cur- rents to operate the translating device, the resistance of the contact between the tongue and revolving drum is not of great importance, and light contact pressure may be employed, thus reducing the mechanical damping of the coil and allowing of increased speed of signalling. automatic working —automatic working has resulted in a very great reduction in the time of transmission of traffic and also in improved accuracy. the monthly statistics carefully compiled by the eastern associated telegraph companies show that the error percentage for automatic working is approximately one-fifth to one-sixth of that for manual working and except for the initial operation of preparing the perforated tape for transmission the system adopted on nearly all main line cables is entirely automatic. as an example, a message handed in in london is dealt with by an operator who by means of a perforator, the keyboard of which resembles that of a typewriter, prepares a perforated paper tape which ts run through a transmitter thus sending into the cable electrical impulses corresponding to the perforationsinthe tape. thesesignals are automatically repeated by apparatus installed at the various stations along the route so that a message for australia, india, south america or china arrives at its destination without any further reperforating or retransmitting by manual means. at the terminal station an automatic perforator produces a tape which is a replica of that originally prepared in london. this in turn passes through a printer which types out the message in the form in which it is delivered. distortion effect and remedy.—the signals received from a cable of any considerable length when working at a speed ap- proaching the maximum, are somewhat distorted and it is un- desirable to retransmit these signals through a number of cables linked together by relays since the distortion is cumulative. cer- tain stations along the route are therefore provided with auto- matic receiving perforators in place of simple relays so that a perforated tape 1s prepared and immediately passed through a transmitter thus sending perfect signals into the next cable and thereby ensuring accuracy and avoiding a reduction in the through speed of transmission. the regenerator—tvhe delay introduced by this method of working, known as tape-translation, 1s small but the recent ad- vent of a system of retransmission employing an instrument known as the “ regenerator ”’ allows of the direct linking up by 746 relays in conjunction with this apparatus of a greater number of cables, thus decreasing the total delay as well as reducing the chance of error by the retransmission of perfectly corrected sig- nals at each stage. the comparatively large tolerance of the regenerator for correctly interpreting distorted signals depends to a great extent on the fact that it is running at exactly the same speed as the transmitter at the distant end of the cable; further, it is also able to follow any slight alteration in the speed of transmission. this is effected by taking the average time of arrival of the signals and comparing it with a predetermined position of a point on the shaft of the retransmitting apparatus. if this time differs, corrections are caused to occur to increase or decrease either momentarily or permanently the speed of the shaft so as to maintain the operative parts on the shaft in con- stant relation to the incoming signal. special precautions are, however, taken to ensure constant speed and both transmitting and receiving instruments are run by phonic motors which are controlled by electrically driven reeds or tuning forks. although the frequency of vibration of the type of reed employed is for nearly all practical purposes constant, a high grade electrical clock is in many cases used to control the reed in order to elimi- nate any small variation due to temperature changes or other causes. performance.—as an example of the speed of transmission, his majesty the king’s message comprising 12 words an- nouncing the opening of the british empire exhibition at wem- bley on april 23 1924 was flashed round the world by the sub- marine cable systems in 80 seconds. the route was as follows:— the stadium-penzance-fayal-halifax by the imperial (british government system). halifax-montreal-vancouver-bamfield-fan- ning-suva-auckland-sydney by the pacific cable board's system. from sydney by two routes, both of the eastern associated com- ee system as follows: (1) sydney-adelaide-perth-cocos- rodriguez - durban - capetown - st. helena - ascension - st. vincent- madeira-porthcurnow-london. (2) sydney-adelaide-darwin-singa- ore - madras - bombay - aden - suez - alexandria - malta - gibraltar- orthcurnow-london. the messages arrived in london simultane- ously at 11:50-55 a.m. having been despatched from the stadium 80 seconds previously at 11:49-35 a.m. the total distance traversed via the south africa route was, in round numbers, 32,300 m. made up of 26,000 m. of cable and 6,300 m. of landline. by the indian route the total was 30,000 miles including roughly 8,200 m. of landline. at the end of 1924 there were some 3,500 submarine telegraph cables in operation, having a totai length of over 332,000 nautical miles, approximately 77,700 m. being administered by the various governments and the remainder by private companies. of the latter approximately 144,000 m. are owned by british companies, 83,000 m. by american companies and the remainder by companies of other countries. since the above date several additional cables have been laid and no less than 26,000 m. were contracted for in the twelve months following june 1924. super posing.—by means of a system introduced by dr. pernot and l. rich three messages are transmitted simultaneously over submarine cables and good results have been achieved on one approximately 1,100 m. in length. the cable is worked duplex in the ordinary manner and in addition, signals are transmitted in one direction by means of an alternating current of a frequency of the order of 40 cycles per second. the direct current for the ordinary duplex working is provided by a small motor-generator the generator field of which is excited from a battery joined up through the contacts of an automatic transmitter. connected in series with the armature of this generator is the stator of a small alternator the field of which is energised from a battery through the contacts of a second transmitter. suitable tuned circuits and filters are included in the circuit at the sending and receiving stations in order to avoid interfer- ence and to separate out the alternating and direct currents. the former are amplified by means of thermionic valves and eventually operate ordinary telegraphic apparatus as employed for direct current working. this system which is a form of “‘ wired wireless ”’ was first installed with very satisfactory re- sults on one of the eastern telegraph company’s cables between gibraltar and malta. the loaded cable-——the submarine cable of the future un- doubtedly will be of the new loaded type. the number of words telegraphy, submarine per minute that can be sent through an ordinary submarine cable is limited owing to the signals being distorted as they pass through the cable, so that at a certain speed they become un- readable. in the loaded cable this distortion is very largely eliminated and on a long cable a working speed in one direction of as much as ten times that of an ordinary cable of similar length may be attained. the loaded cable is so named because of its peculiarities being similar to a certain mechanical analogy. the ordinary cable can be likened to a light rope stretched tightly in water and the process of signalling to lateral movements at one end that cause waves to pass along the rope. these waves will rapidly diminish in size due to the friction of the water, but if the rope be weighted or “‘ loaded ” with weights at short in- tervals, the waves will travel along the rope with much less loss of size, owing to there being more energy associated with the waves. the loading of a cable is obtained by increasing its inductance or electrical mass. one method of accomplishing this is to insert at intervals along the cable loading coils comprising an insulated conductor wound around a metal that will become magnetised when a current is passing through the cable and winding. the insertion of these coils presents mechanical difficulties, especially where the cable is to be laid in deep water as would usually be the case where a long cable is concerned, and the necessity for an increase of speed most apparent. it may, however, be possible to introduce induc- tance in this form, known as “ lump loading ” into existing cables which are not laid in very deep water. the possibilities of loading have been realised for many years, and cables loaded with soft iron wire were laid over twenty years ago for telephone purposes. the small increase of inductance due to soft iron makes it un- suitable for use for long telegraph cables and it is the recent development of nickel-iron alloys that has made the loaded tele- graph cable a successful project. (see telegraphy.) continuous loading—the introduction of these nickel-iron alloys of high permeability for low magnetising forces has made it possible to employ “‘ continuous loading ”’ which does not alter the present regular form of the cable or add to the difficulties of laying or raising for repair. this alloy is employed in the form of a fine wire or tape which is wound continuously and directly around the copper conductor before the gutta percha insulating sheath is applied. the first telegraph cable of this description was manufactured in england and laid for the western union tele- graph company in sept. 1924 to connect new york with horta in the island of fayal, azores. another cable was laid in march 1926 for the eastern extension company to connect cocos island with perth, western australia. a cable of this type can work at a very high speed when com- pared with an unloaded cable of the same length and having similar weights of copper and gutta percha per mile. on such a cable the actual specd in letters per minute attainable is above that of any automatic receiving apparatus at present available for directly printing the received traffic or for producing a per- forated tape which can be utilised for operating a printer. the use of receiving apparatus comprising thermionic valves and a specially constructed high speed siphon recorder would necessitate the introduction of a manual operation for preparing the mes- sage for retransmission or delivery, such as perforating, writing or typing from the tape on which the signals are recorded and this would undoubtedly result in delay and increased percentage of error. it therefore appears likely that a multiplex system such as em- ployed on fast landlines will eventually best meet the require- ments, so that several messages will be transmitted to all intents and purposes simultaneously. for example, by adopting the baudot or similar system it would, no doubt, be possible to oper- ate a number of channels up to say, six, each dealing with about 40 words per minute. experiments are also being made with a view to the simulta- neous transmission of signals by alternating currents at differ- ent frequencies, these being separated out at the receiving end by means of tuned circuits and filters. the problem of “ du- plexing ” a loaded cable presents a number of difficulties but teleki-—-telephony research work is being carried out with a view to the production of a satisfactory “‘ artificial line” to copy as nearly as possible the characteristics of the cable. (j: d-p.s neocyg. w-) teleki, paul, count (1879- ), hungarian politician and geographer, studied jurisprudence and geography in buda- pest. after being elected to parliament in 1905 he spent some years in geographical study abroad, and published aas zur ge- schichte der kartographie der japanischen inseln (budapest, 1909), which was crowned with the prix jomard by the french societe de geographie. during the early part of the world war he served as an automobile officer in the campaign against serbia and found time to prepare a handbook on the history of geo- graphical thought (1917). when the revolution broke out he retired from public work and produced a number of ingenious maps showing the national minority problems and economic situ- ation of hungary. teleki organised the scientific side of the prep- arations for the peace conference, making an exhaustive and enlightening exposition of the hungarian case. he was appointed minister for foreign affairs in the first parliamentary cabinet of admiral horthy, the regent (april 1920), and in july of the same year became prime minister. he resigned in 1921 after the first attempt of king charles to regain his throne. later in the year he was appointed professor of economic geography in the univer- sity of budapset. in 1924 he served in a scientific capacity on the commission appointed by the league of nations to enquire into the mosul frontier dispute bet ween great britain and turkey, teleki’s works include, besides those already mentioned, the evolution of hungary and its place in european iistory (new york, 1923); ethnographical map of hungary (1920); economic geography of america (1922, hungarian). telepathy: see psychical research.