Figure 80 represents a side elevation of the dial and clock work of the _receiving station_. A represents an edge view of the electro magnet, from which proceed the two wires, _v_ and _i_, which connect with the wires, _n_ and _p_, of figure 79. J and J is the brass frame containing the wheel work, C and E; the pin wheel, D; the dial plate, I; and the barrel, B, which is driven by a weight and cord. In the side of the wheel, D, are pins projecting from the rim, parallel with the axis, and are equal in number to the divisions, or letters, upon the dial, I. They are, however, placed alternately on each side of the rim. F is the armature of the magnet, fastened upon a horizontal rod, sliding freely through the standards, 1 and 2. G represents a spring, fastened to the frame, J, and which carries back the armature, F, when the magnet has ceased to attract it. From the armature there extends downward an arm, K, which, as it approaches the pin wheel, D, presents two arms, or pallets, one on each side of the wheel. These pallets are so arranged with regard to the pins, that if one pallet releases a pin on one side of the wheel, the same movement will cause the other pallet on the other side, to arrest the motion of the wheel by its striking against the next alternate pin. H and I is an edge view of the circular dial, enclosed in a case, with a single opening at O, so that only one letter at a time can be seen. This dial, I, is in every respect marked as the disc in figure 79. Figure 81 represents the two instruments. O the _transmitting_ instrument, and the right hand figure the _receiving_ instrument. The wires, _v_ and _i_, are respectively connected with _p_ and _n_. It will be observed, that the armature, F, is not attracted, and that the right hand pallet is checking the pin wheel, so that the dial is stationary. If, however, the disc, _t_, is turned so that the circuit is completed, by the contact of the spring, _e_, with one of the ribs, instantly the armature is attracted by the electro magnet, which will carry the right hand pallet away from the pin wheel, and which will then move by the action of the weight upon the barrel, B, until it is checked by the left hand pallet, which had advanced to the wheel at the same time the other receded. This single operation has moved the disc one division and the armature is still attracted. Now let the disc, _o_, be turned until the spring, _e_, has been passed by the rib, and is in contact with the ivory only, instantly the current ceases; the armature, F, recedes from the magnet by the action of the spring, G; this has taken the left hand pallet from the pin wheel, which is permitted to move until the next pin strikes against the right hand pallet. This has now brought another letter in front of the aperture at H. Thus it will be seen, that the design of this instrument is to bring into view, at the aperture such letters as are required in transmitting a message. [Illustration: FIG. 81.]