History of the Atlantic Cable & Undersea Communications
Wheatstone's Automatic Printing Telegraph
[From the Comptes Rendus de l'Académie des Sciences, 1859, tome xlviii. pp. 214-220.]
DESCRIPTION OF THE AUTOMATIC PRINTING TELEGRAPH
BY C. WHEATSTONE F.R.S.,
CORRESPONDING MEMBER OF THE ACADEMY OF SCIENCES AT PARIS, ETC.
From the Comptes Rendus of the Academy for January 24, 1859*
I have the honour to submit to the Academy a new Automatic Printing Telegraph, which, I believe, possesses advantages which have hitherto been unattained. With the instrument at present on the table 500 letters per minute have been printed. The perforated bands of paper, which determine the order and succession of the electric currents by a means analogous to the mechanism of a Jacquard loom, are prepared in such manner that the groups of points constituting the different letters are distinctly separated, so as to render any mistake arising from the coalescence of adjacent letters, which now frequently happens, impossible; and effective ink-marks are impressed on paper without adding in the least to the weight, or causing any resistance to the moving parts of the electro-magnets.
This invention consists of a new combination of mechanism, for the purpose of transmitting messages previously prepared through a telegraphic circuit, and causing them to be printed at a distant station.
Long strips of paper are perforated by a machine, constructed for the purpose, with apertures grouped to represent the letters of the alphabet and other signs; a strip thus prepared is placed in an instrument associated with a rheomotor (or source of electric power), which on being set in motion, moves it along, and causes it to act on two pins, in such manner that when one of them is elevated the current is transmitted to the telegraphic circuit in one direction, and when the other is elevated it is transmitted in the reverse direction: the elevations and depressions of these pins are governed by the apertures and intervening intervals. These currents following each other indifferently in these two opposite directions, act upon a writing instrument at a distant station, in such manner as to produce corresponding marks on a slip of paper moved by appropriate mechanism.
I will proceed more particularly to describe the several parts of this telegraphic system: observing, however, that each part has its independent originality, and may be associated with other apparatuses already known.
The first apparatus is a perforator, an instrument for piercing the slips of paper with the apertures in the order required to form the message. The slip of paper passes through a guiding groove, at the bottom of which an opening is made sufficiently large to admit of the to and fro motion of the upper end of a frame containing three punches, the extremities of which are in the same transverse line. Each of these punches, the middle one of which is smaller than the two external ones, may be separately elevated by the pressure of a finger-key. By the pressure of either finger-key, simultaneously with the elevation of its corresponding punch, in order to perforate the paper, two different movements are successively produced—first, the raising of a slip which holds the paper firmly in its position, and secondly, the advancing motion of the frame containing the three punches, by which the punch which is raised carries the slip of paper forward the proper distance; during the reaction of the key, consequent on the removal of the pressure, the slip first fastens the paper, and then the frame falls back to its normal position. The two external keys and punches are employed to make the holes, which grouped together represent letters and other characters, and the middle punch to make holes which mark the intervals between the letters. The perforations in the slip of paper appear thus:—
A very simple addition to the perforator enables a printed message which has been received to be retransmitted to a more distant station, without any translation or knowledge of the meaning of the message. The printed band which has been received is made to pass between two rollers, one of which is movable by a finger screw, so as to cause the characters to pass successively before the eyes of the operator. The keys of the perforator are acted upon with the right hand, and the finger-screw with the left; as the characters successively appear the keys are pressed down in the order of the points of which the letters consist, an operation which scarcely requires any skill to perform.
There need be no change in the alphabet which is at present employed; the points at one side may represent the short dashes, and those at the other side the long dashes, their order remaining the same as in the existing system.
The second apparatus is the transmitter, the object of which is to receive the slips of paper prepared by the previously described instrument, or perforator, and to transmit the currents produced by a voltaic battery or other rheomotor, in the order and direction corresponding to the holes perforated in the slip. This it effects by mechanism somewhat similar to that by which the perforator performs its functions.
An eccentric produces and regulates the occurrence of three distinct movements:
1st. The to and fro motion of a small frame which contains a groove fitted to receive the slip of paper, and to carry it forward by its advancing motion.
2nd. The elevation and depression of a spring-clip, which holds the slip of paper firmly during the receding motion, but allows it to move freely during the advancing motion.
3d. The simultaneous elevation of three wires placed parallel to each other, resting at one of their ends, over the axis of the eccentric, and their free ends entering corresponding holes in the grooved frame.
These three wires are not fixed to the axis of the eccentric, but each of them rest against it by the upward pressure of a spring, so that when a light pressure is exerted on the free ends of either of them, it is capable of being separately depressed. When the slip of paper is not inserted, and the eccentric is in action, a pin attached to each of the external wires touches, during the advancing and receding motions of the frame, a different spring, and an arrangement is adopted by means of insulation and contacts properly applied, by which, while one of the wires is elevated and the other remains depressed, the current passes from the voltaic battery to the telegraphic circuit in one direction, and passes in the other direction when the wire before elevated is depressed, and vice versa;but while both wires are simultaneously elevated or depressed, the passing of the current is interrupted. When the prepared slip of paper is inserted in the groove and moved forward, whenever the end of one of the wires enters an aperture in its corresponding row, the current passes in one direction, and when the end of the other wire enters an aperture of the other row, it passes in the other direction. By this means the currents are made to succeed each other automatically, in their proper order and direction, to give the requisite variety of signals. The middle wire only acts as a guide during the operation of the current.
The wheel which drives the eccentric may be moved by the hand or by the application of any motive power.* Were the movement of the transmitters effected by machinery, any number may be attended to by one or two assistants.
This transmitter requires only a single telegraphic wire. If desired, the despatch may have only a single row of apertures; in this case the perforator must have only two keys, and the transmitter two pens instead of three.
The third apparatus is the recording or printing apparatus, which prints or impresses legible marks on a strip of paper corresponding in their arrangement with the apertures in the perforated paper.
The pens or styles are elevated and depressed by their connection with the moving parts of the electro-magnets. The pens are entirely independent of each other in their action, and are so arranged that when the current passes through the coils of the electro-magnet in one direction one of the pens is depressed, and when it passes in the contrary direction the other is depressed; when the currents cease light springs restore the pens to their elevated point.
The mode of supplying the pens with ink is as follows:—A reservoir about an eighth of an inch deep, and of any convenient length and breadth, is made in a piece of metal, the interior of which may be gilt, in order to avoid the corrosive action of the ink placed in it; at the bottom of this reservoir are two holes, sufficiently small to prevent by capillary attraction the ink from flowing through them; the ends of the pens are placed immediately above these small apertures, which they enter, when the electro-magnets act upon them, carrying with them a sufficient charge of ink to make a legible mark on a ribbon of paper passing beneath them. The motion of the paper ribbon is produced and regulated by apparatus similar to those employed in other register or printing telegraphs.
The fourth improvement is an instrument which I call a translator. Its object is to translate the telegraphic signs, consisting of successions of points or marks, adopted in this system, into the ordinary alphabetic characters. In the system I have adopted, limiting the number of points in succession to four, 30 distinct characters are represented. The instrument presents externally nine finger stops, eight of which are arranged in two parallel rows, four in each, and the remaining one is placed separately. The principal part of the mechanism within is a wheel, on the circumference of which 30 types are placed at equal distances, representing the letters of the alphabet and other characters; other mechanism is so disposed and connected thereto, that when the keys of the upper row are respectively depressed, the wheel is caused to advance 1, 2, 4, or 8 steps or letters, and when those of the lower row are, in like manner, depressed, the wheel advances respectively 2, 4, 8, or 16 steps. By this disposition, when the stops are touched successively in the order in which the points are printed on the paper, touching the first stop for one point, the first and second for two points, &c., and selecting the stops of the upper or lower row, according as the point is in the upper or lower row of the printed ribbon, the type wheel will be brought into the proper position for placing the letter corresponding to the succession of points over a ribbon of paper. The ninth stop, when it is pressed down, acts to impress the type on the paper, to cause the advance of the paper, in order to bring a fresh place beneath the type wheel, and subsequently to restore the type wheel to its initial position.
I will conclude by offering a few remarks on the advantages possessed by this system.
Whatever practical dexterity may be acquired by a voluntary operator, the result arrived at will be far inferior to that obtained by the automatic process, which is only limited by the rapidity with which the recurring motions of the transmitter can be effected. By the present construction of the instrument, five times the quantity of signs at present used can be transmitted to moderate distances; though for very considerable distances this rapidity may be limited in conductors subjected to inductive influences, by the tendency which rapidly recurring short currents have to coalesce.
But even if there were no advantage in point of rapidity possessed by the automatic over the voluntary process of transmission, its other advantages would be incontestable. For the profitable working of a telegraphic line, it is necessary that the operator should manipulate as rapidly as is consistent with a correct transmission of the message; it requires great skill to become proficient in such manipulations, even when the language in which the despatch is sent is quite familiar to the operator; but if he would send a despatch in a language unknown to him, or in cipher, he is obliged to proceed with caution and slowness. In my new system, the prepared messages are transmitted with equal rapidity in whatever language or cipher they may be; and as the perforated bands may be prepared at leisure, and be subjected even to the revision of a corrector, guarantees of accuracy are obtained which cannot be afforded by the system of immediate voluntary transmission. Several clerks will be required to prepare messages for a single telegraphic line in constant activity; but in an economical point of view their time is of far less importance than the time occupied by the transmission of a message.
Another advantage this new system possesses is, that the same prepared message may be transmitted through any number of distinct lines, if not simultaneously, at least in such rapid succession as to be equivalent thereto; and besides, without any fresh labour, the same message may be retransmitted if thought necessary; and service messages in constant use may be preserved for transmission whenever they may be required. _
Were this automatic system generally adopted it might, in many instances, be more convenient to prepare the messages at the offices from which they are sent, the instrument for effecting this purpose being very portable and of small cost. The operations at the telegraph office would, in these cases, be limited to passing the perforated band through the transmitter at one station and receiving the printed message at the other, the translation as well as the preparation of the message devolving on the department of the administration to which it relates.
In the present case it is not the question to substitute one kind of acquired skill for another kind equally difficult to attain, which would entail great labour on all the employees. The great practical dexterity at present required being dispensed with, and the principal and most laborious operation being entirely automatic, there is little to learn though there may be something to forget.
Scientific & technical papers of Werner von Siemens, Vol. I, 1892, p.136.
REMARKS ON WHEATSTONE'S AUTOMATIC WRITING TELEGRAPH*
At the meeting of the 24th January, Mr. Wheatstone submitted to the Academy an automatic writing telegraph, with reference to which I propose to make the following remarks :—
The idea of transmitting telegraphic messages by means of a perforated strip of paper is in the first place very old and due to Mr. Bain. I remember that when I was in Paris, in the spring of 1850, Mr. Bain set an electro-chemical telegraph at work by means of a strip of perforated paper, at a meeting of the Academy at which I had the honour to be present.
Since that time, Mr. Halske and I have been much engaged with the application of the same method to Mr. Morse's telegraphs. Since the year 1855 we have supplied apparatus of this kind, called tachygraphs, on the line we have constructed from Warsaw to St. Petersburg. In the same year one of our tachygraphs was working at the great exhibition in the Champs Elysees, alongside of our apparatus intended for the simultaneous transmission of messages in opposite directions. The perforating apparatus with which our tachygraph was provided, used for perforating the strip of paper, only differed from that of Mr. Wheatstone just described by its greater simplicity. Long before Mr. Wheatstone's last communication to the Academy, we like him had used currents directed alternately in opposite directions for working our tachygraph, instead of currents and periods of rest alternately, and used strips of perforated paper to allow these currents to pass at the desired intervals. Lately, however, we have given up the use of these strips, having replaced them by movable type similar to printing type, and representing the different characters of the Morse alphabet. The operator prepares the message by arranging the type one after the other in the grooves, passed through the apparatus by clockwork. These types bring a commutator into play, which causes the current to pass in one direction or the other, according as the position of its reciprocating motion is determined by the passage of the types.
* Comptes Rendus, 1859, Vol. XLVIII. p. 468.
Last revised: 11 September, 2011