June 30, 1910J 



NATURE 



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o4o 



paration of the transmitting slip will always, of course, be 

 necessary in all automatic systems, but inventors have 

 turned their attention to increasing the speed and reducing 

 the cost of transcription at the received end, in the case 

 of manual as well as automatic sending, by the substitution 

 of typing apparatus worked mechanically or electrically for 

 the manual transcription. A very considerable number of 

 instruments has been designed to achieve this end, but 

 one of the earliest, which has met with permanent success, 

 and by means of which a very large proportion of the 

 work in Europe and nearly the whole of the Trans- 

 continental work is dealt with, is the well-known Hughes's 

 type-printing instrument. 



The Hughes method of transmission has many 

 advantages. It provides a clearly typed message for 

 delivery instead of a written one, it removes a possible 

 source of error in transcription, and it increases the speed 

 of working as compared with Morse by about 25 per cent. 

 It can be duplexed, and it is used by the Post Office on 

 all its Continental wires. It has, however, the dis- 

 advantage that a considerable interval of time elapses 

 between the transmission of two consecutive signals owing 

 to the revolving arm having to traverse all the intervening 

 letters. Baudot has obviated this waste of time by adopt- 

 ing the multiple system of telegraphy. He entirely 

 abandons the Hughes method of transmission, and he forms 

 an arbitrary signal code which, by means of five con- 

 secutive currents, some plus, some minus, in combina- 

 tion, he represents each letter of the alphabet, figures, or 

 other signals. By his method he can provide four or six 

 channels simultaneously on one wire, each being worked 

 manually. 



The Baudot system admits of the transmission of a much 

 larger number of messages over each wire than the 

 Hughes. It is also more flexible, inasmuch as the various 

 channels it provides can be divided amongst an equal 

 number of towns ; thus Paris can use two channels to 

 Lyons and two to Marseilles over a Paris-Lyons circuit 

 extended from Marseilles, and so on. It is largely used 

 in France, and has been introduced into this countrj*. 



It will have been observed from the foregoing that there 

 are three distinct methods of telegraphic transmission with 

 which we are mainly concerned to-night, although others 

 might be mentioned. In the first, an arbitrary code of 

 signals is repeated in similar arbitrary signals by which 

 the alphabet is artificially represented, and the message is 

 read by a skilled operator ; in the second, what may be 

 termed the dial type of apparatus is used, where two tjpe- 

 wheels, either moved mechanically or electrically, revolve 

 isochronously, and they may either show fleeting letters 

 or print them in permanent characters ; and in the third, 

 an arbitrary set of electrical signals is devised which 

 actuates specially designed apparatus which may repro- 

 duce the message in legible characters, printed, or even 

 written. The third method has been utilised by various 

 inventors and applied to automatic transmission, so as to 

 dispense with manual transcription at the receiving 

 station. 



In all cases a paper ribbon or slip is perforated by 

 punches generally actuated by a specially designed type- 

 writer keyboard, in which the depression of any key causes 

 a series of perforators representing the arbitrary combina- 

 tion of the corresponding letter to appear on the slip. 

 This is passed through an automatic transmitter ; the elec- 

 trical currents corresponding with the perforators are 

 transmitted over the circuit, and the distant apparatus 

 actuated. 



Murray has devised a system which has undergone 

 lengthy trials both at home and abroad. His slip has one 

 row of perforations which gears into the moving mechanism 

 of the transmitter, and below this a second series of per- 

 forations which represent his artificial signalling code, 

 which is of the Baudot type. At the receiving apparatus 

 an exact counterpart of the transmitted slip with its per- 

 forations is reproduced, and this perforated slip is passed 

 through and actuates an automatic type-writer, which 

 prints the message. 



Creed has worked in the same direction, but he uses 

 the ordinary Wheatstone alphabet already described, and. 

 of course, the Wheatstone transmitter. At the receiving 

 end a perforated Wheatstone slip is reproduced by a punch- 

 ing machine, which, controlled by the reverse currents from 



NO. 2122, VOL. 83] 



the transmitter, and, using compressed air as a motive- 

 power, perforates the received slip at considerable speed. 

 This slip is then passed through an automatic type-writer 

 adapted to work with the Wheatstone alphabet, which 

 types the message on a long slip, to be gummed on the 

 telegraph form. In both these cases the received slip can 

 be inserted in a second automatic transmitter and the 

 message sent on to another town — an advantage in the 

 transmission of news, which frequently has to be re- 

 distributed from large provincial centres to other towns 

 having no direct communication with London. Both these 

 systems are in use in the British Post Office. 



Siemens and Halske in Berlin have devised an automatic 

 system in which, by means of suitable apparatus, the 

 message is printed by the receiving apparatus direct by 

 photographic methods. 



Writing telegraphs, based on the fact that two ordinates 

 at right angles to one another can be made to describe any 

 curve, have been designed. The telewriter, in which the 

 pen is connected to two arms which follow the movements 

 of the writer, and which in doing so pass over varjing 

 resistances and transmit to line currents of varying 

 strength, is well known. At the receiving end two pivoted 

 electromagnets, placed in a very powerful magnetic field, 

 are deflected over arcs dependent on the strength of the 

 current circulating at any moment. Two arms at right 

 angles to one another are connected to the transcribing 

 pen, one arm being pivoted to each magnet, and the 

 writer's movements are reproduced. 



There is only time to refer briefly to the beautiful writing 

 apparatus designed by Pollak and Virag. In this a slip 

 is perforated by suitable means with nine rows of holes 

 of varying sizes ; suitable flexible brushes make contact 

 through these holes between batteries and the line wires, 

 and thus cause currents of different electromotive forces 

 and duration to circulate over the line, and to act on two 

 telephone receivers at right angles to one another. Rays 

 of light are reflected from one to the other and on to a 

 photographic slip, and the written messages, which can be 

 transmitted at 600 to 1000 words a minute, appear 

 developed and fixed on the sensitised paper which emerges 

 from the dark closet of the apparatus. 



Submarine telegraphy is not susceptible of the many 

 developments that have been possible with land-lines. The 

 high electrostatic capacity, varying from 03 to 0-4 micro- 

 farad per mile, and the very long lengths that are neces- 

 sary to connect the great continents of the world, render- 

 ing the use of any but the most delicate apparatus 

 impossible on long cables. The receiving instruments 

 originally invented by the late Lord Kelvin, then Sir 

 William Thomson, are still the only apparatus available 

 for the reception of messages on long Transcontinental 

 cables, and so far it has not been found possible to increase 

 materiallv the speed of working except, of course, by 

 increasing the dimensions and cost proportionately. 



In ordinary telegraphy, when transmitting through an 

 overhead line, the frequency of the current alternations is 

 only i8o per second for 450 words per minute, and the 

 current has actuated the apparatus at the further end 

 before the battery connection has ceased. Another con- 

 dition, however, is introduced when a conductor is used 

 for telephonic speech in which a maximum frequency of 

 1800 to 2000 vibrations per second has to be dealt with. 

 In these cases the transmission from the telephone assumes 

 complex wave-forms, and the effect of even a moderate 

 capacity- becomes far more marked than in the case of 

 telegraphic transmission. If a simple w-ave impulse were 

 emitted in a circuit containing neither capacity nor induct- 

 ance it would maintain its form, and it would only lose 

 in amplitude owing to the waste of energy in heating the 

 conductor. With much capacity in the circuit, however, 

 the wave tends to elongate, and if the capacity be 

 sufficiently great and the line sufficiently long, the follow- 

 ing wave overtakes the lagging tail of the previous one ; 

 they blend more or less together, and having lost their 

 distinctive character they fail to impress on the receiving 

 telephone the distinct character of the sound from which 

 they emanate. 



The loss of the overtones means diminution of the 

 timbre of the voice ; in other words, through speech may 

 still be possible, but the voice ultimately becomes less 

 recognisable until, when a certain limit is passed, if the 



