Edison, His Life and Inventions [324]
surface and the ground a diaphragm sounder, which is preferably one of my electromotograph telephone receivers. The key normally short-circuiting the revolving circuit-breaker, no impulses are produced in the induction coil until the key is depressed, when a large number of impulses are produced in the primary, and by means of the secondary corresponding impulses or variations in tension are produced at the elevated condensing surface, producing thereat electrostatic impulses. These electrostatic impulses are transmitted inductively to the elevated condensing surface at the distant point, and are made audible by the electromotograph connected in the ground circuit with such distant condensing surface."
The accompanying illustrations are reduced facsimiles of the drawings attached to the above patent, No. 465,971.
V
THE ELECTROMOTOGRAPH
IN solving a problem that at the time was thought to be insurmountable, and in the adaptability of its principles to the successful overcoming of apparently insuperable difficulties subsequently arising in other lines of work, this invention is one of the most remarkable of the many that Edison has made in his long career as an inventor.
The object primarily sought to be accomplished was the repeating of telegraphic signals from a distance without the aid of a galvanometer or an electromagnetic relay, to overcome the claims of the Page patent referred to in the preceding narrative. This object was achieved in the device described in Edison's basic patent No. 158,787, issued January 19, 1875, by the substitution of friction and anti- friction for the presence and absence of magnetism in a regulation relay.
It may be observed, parenthetically, for the benefit of the lay reader, that in telegraphy the device known as the relay is a receiving instrument containing an electromagnet adapted to respond to the weak line-current. Its armature moves in accordance with electrical impulses, or signals, transmitted from a distance, and, in so responding, operates mechanically to alternately close and open a separate local circuit in which there is a sounder and a powerful battery. When used for true relaying purposes the signals received from a distance are in turn repeated over the next section of the line, the powerful local battery furnishing current for this purpose. As this causes a loud repetition of the original signals, it will be seen that relaying is an economic method of extending a telegraph circuit beyond the natural limits of its battery power.
At the time of Edison's invention, as related in Chapter IX of the preceding narrative, there existed no other known method than the one just described for the repetition of transmitted signals, thus limiting the application of telegraphy to the pleasure of those who might own any patent controlling the relay, except on simple circuits where a single battery was sufficient. Edison's previous discovery of differential friction of surfaces through electrochemical decomposition was now adapted by him to produce motion at the end of a circuit without the intervention of an electromagnet. In other words, he invented a telegraph instrument having a vibrator controlled by electrochemical decomposition, to take the place of a vibrating armature operated by an electromagnet, and thus opened an entirely new and unsuspected avenue in the art.
Edison's electromotograph comprised an ingeniously arranged apparatus in which two surfaces, normally in contact with each other, were caused to alternately adhere by friction or slip by reason of electrochemical decomposition. One of these surfaces consisted of a small drum or cylinder of chalk, which was kept in a moistened condition with a suitable chemical solution, and adapted to revolve continuously by clockwork. The other surface consisted of a small pad which rested with frictional pressure on the periphery of the drum. This pad was carried on the end of a vibrating arm whose lateral movement was limited between two adjustable points. Normally, the frictional pressure between the drum
The accompanying illustrations are reduced facsimiles of the drawings attached to the above patent, No. 465,971.
V
THE ELECTROMOTOGRAPH
IN solving a problem that at the time was thought to be insurmountable, and in the adaptability of its principles to the successful overcoming of apparently insuperable difficulties subsequently arising in other lines of work, this invention is one of the most remarkable of the many that Edison has made in his long career as an inventor.
The object primarily sought to be accomplished was the repeating of telegraphic signals from a distance without the aid of a galvanometer or an electromagnetic relay, to overcome the claims of the Page patent referred to in the preceding narrative. This object was achieved in the device described in Edison's basic patent No. 158,787, issued January 19, 1875, by the substitution of friction and anti- friction for the presence and absence of magnetism in a regulation relay.
It may be observed, parenthetically, for the benefit of the lay reader, that in telegraphy the device known as the relay is a receiving instrument containing an electromagnet adapted to respond to the weak line-current. Its armature moves in accordance with electrical impulses, or signals, transmitted from a distance, and, in so responding, operates mechanically to alternately close and open a separate local circuit in which there is a sounder and a powerful battery. When used for true relaying purposes the signals received from a distance are in turn repeated over the next section of the line, the powerful local battery furnishing current for this purpose. As this causes a loud repetition of the original signals, it will be seen that relaying is an economic method of extending a telegraph circuit beyond the natural limits of its battery power.
At the time of Edison's invention, as related in Chapter IX of the preceding narrative, there existed no other known method than the one just described for the repetition of transmitted signals, thus limiting the application of telegraphy to the pleasure of those who might own any patent controlling the relay, except on simple circuits where a single battery was sufficient. Edison's previous discovery of differential friction of surfaces through electrochemical decomposition was now adapted by him to produce motion at the end of a circuit without the intervention of an electromagnet. In other words, he invented a telegraph instrument having a vibrator controlled by electrochemical decomposition, to take the place of a vibrating armature operated by an electromagnet, and thus opened an entirely new and unsuspected avenue in the art.
Edison's electromotograph comprised an ingeniously arranged apparatus in which two surfaces, normally in contact with each other, were caused to alternately adhere by friction or slip by reason of electrochemical decomposition. One of these surfaces consisted of a small drum or cylinder of chalk, which was kept in a moistened condition with a suitable chemical solution, and adapted to revolve continuously by clockwork. The other surface consisted of a small pad which rested with frictional pressure on the periphery of the drum. This pad was carried on the end of a vibrating arm whose lateral movement was limited between two adjustable points. Normally, the frictional pressure between the drum