What has just been said with regard to the C circuit also applies to the circuit of B when the pen is removed from right to left, the pole changer, D, being then operated by the lower pulley and arm, B, so as to change the polarity of the current, according as the motion is from left to right, or vice versa.
We now come to the operation of the receiving instrument, which is shown in Fig. 21. This consists of a pen, connected by means of a tube with a supply of ink, shown at the right, adjoining the upper receiving magnets. The pen is connected to two rods, which are placed at right angles to each other, similar to the cords in the transmitter, and are jointed, SO as to have a free movement sidewise. One of these rods passes through the frame carry ing the magnets, II II, which are included in the circuit of the interrupter, C, of the trans matter, and are provided with armatures, which act upon the rod in such a manner as to impart a step by-step movement to it in opposite directions, according as one or the other of the magnets is energized. The rod and the magnets, I/ , and then armatures, are so ar ranged that the rod passes between the adjacent ends of the two parts of each armature in such a manner that, when the two parts of either armature are moved toward each other, they will act first to grip the rod between them, and being then moved toward the magnet, they will carry the rod with them, and impart a corresponding movement to the pen, C.
In connection with the magnets, II II, there is a polarized relay, I, which is so arranged that when its armature is on one contact, due to a current coining over the line in a certain direction, it sends that current into the lower magnets, 1I11; but when a current of opposite polarity comes over the line, it is carried to Lhe other stop, and the current is sent into the upper magnets, Lhe lower magnets being then short-circuited.
Now, it will be readily seen that when the pen, _A, at the transmitting station is moved upward, it sends current pulsations of one direction over the line. These axe received by the relay, I, and sent into the lower magnets, IIII, which act, as described above, to grip and raise the rod to correspond exactly with the number of pulsations, which, of course, are deter mined by the amount of movement given to the transmitting pen, A. When the latter is
moved downward, the current impulses are sent in similar way into theupper magnets, which grip and lower the rod in an analogous manner at each pulsation. Time identical action also takes place with the current transmitted over the main line, connected to the inter rupter, II, the current passing into the relay, I, and magnets, /17.1i, which act upon the rod at angles to the first to move the pen sidewise in either direction.
From this it follows that any movement of the transmitting pen in any direction oblique to the line, or intermediate between these two directions, will cause the receiving pen to move in a corresponding direction, but with a compound movement made up of a number of steps taken at right angles to or crosswise of each other, the relative number of steps in each direc tion depending upon the obliquity of the direction in which the transmitting pen is moved. By this means the receiving pen is caused to substantially follow any movement of the trans mitting pen, and thus reproduce a facsimile of whatever is written or traced by the latter.
Tke Writing Telegroph.—This is the latest and most perfect form of the Cowper telegraph, and is being used in this country by the Writing Telegraph Co. with many radical improvements. The system consisted in the use of a transmitter, which served to vary, the current on two lines connected to the receiver. The latter consisted of a pair of electromagnets placed at right angles to each other, and acted upon an armature which followed exactly the movements of a stylus in the transmitter ; this stylus served to VII y the currents on z,he connecting lines by cutting in or out a set of resistances.
The transmitter, which fully meets all the requirements for electric writing, is the invention of Mr. Harry Etheridge. This part of the apparatus, which is shown in perspective in Fig. 22. consists of a top plate, which rests on the top of the case. A rod depends from this plate and supports the base. Scented to this base, and arranged at right angles to each other, arc two receptacles, in which two series of steel spring tongues, S are separately held in a vertical position by an insulating cement.