We borrow from the Elektrotechnische Zeitung the following details in regard to the telephonic installations made by the Brothers Naglo at Berlin. Fig. 1 gives the general arrangement of a station, where J is an inductor set in motion through a winch, K, and a pair of friction rollers; W, a polarized call; U, an ordinary two-direction commutator; B, a lightning protector; and L and T, the two terminals of the apparatus, one of them connecting with the line and the other with the earth. The interesting point of this system is the automatic communication which occurs when the inductor, J, is moved. At the same moment that the winch, K, is being moved, the disk, P, is carried from right to left and brought into contact with the spring, f. As soon as the winch is left to itself a counter-spring forces the disk, P, to return to a contact with the spring, f. Figs. 2 and 3 show the details of such communication. The winch, K, is keyed to one of the extremities of a sleeve that carries the disk, P, at its other extremity. This sleeve is fixed upon the axle of the first friction roller, that is to say, upon the axle that controls the motion of the inductor, and is provided at the center with two helicoidal grooves, e, at right angles with one another.
In these grooves slides a tappet, n, connected with the axle.
Under the influence of the counter-spring at the left of the disk, P, the latter constantly tends to occupy the position shown in Fig. 2, which is that of rest. As soon as the winch, K, is revolved, whatever be the direction of the motion, the axle can only be carried along when the tappet, n, has come to occupy the position shown in Fig. 3, that is to say, when the disk has moved from right to left a distance corresponding to the fraction of the helix formed in the sleeve.
This stated, it is easy to understand the travel of the currents. Fig. 1 shows the station at rest. The current that arrives through L passes through the lightning protector, the body of the commutator, U, the terminal, v, and the call, W, bifurcates at P, and is closed by the earth. The inductor is in circuit, but, as it is in derivation, upon a very feeble resistance, v, nearly the whole of the current passes through the latter. When it is the station that is calling, the call, W, is put in derivation upon the circuit, f p, h, so that the portion of the circuit that passes through q W v is exceedingly feeble, and incapable of operating the bell of the post that is calling.
FIGS. 2 AND 3.
Finally, when the telephone is unhooked, the inductor, J, and the bell, W, are thrown out of circuit, and the telephone is interposed between d and i, that is, between L and T. - La Lumiere Electrique.