_M. de Weinhold’s System._--M. Zetzche speaks highly of an alarum devised by Professor A. de Weinhold, which resembles that by M. Lorenz, represented in fig. 56. Its organ of sound consists of a steel bell T, from 13 to 14 centimètres in diameter, and toned to give about 420 double vibrations in a second. ‘Its diameter and tone,’ he says, ‘are important, and any great departure from the rule laid down diminishes the effect. The opening of the bell is below, and it is fixed on a stand by its centre. A slightly curved bar magnet, provided at its two ends with iron appendices enclosed in a coil, traverses the stand. The bar magnet of the telephone also terminates in an iron appendix enclosed in a coil. In both cases the changes produced in the magnetic condition appear to be more intense than they are in magnets without appendices. The bar magnet is placed within the bell in the direction of one of its diameters, so that the appendices almost touch its sides. ‘When the bell is struck on a spot about 90° from this diameter with a wooden clapper M, which acts with a spring, and is withdrawn by stretching the spring and then letting it go, as in a bell for the dinner-table, the vibrations imparted to it send currents into the coils, and these currents produce identical vibrations on the iron disk of the telephone, which are intensified by a conical resonator fitted to the telephone, so as to be easily heard some paces off. For ordinary use, the bell coil is broken into a short circuit by means of a metallic spring R, and consequently, when the bell is struck, the spring must be opened so as not to break the circuit. An instrument of the same kind has also been devised by Herr W. E. Fein at Stuttgardt.’ [Illustration: FIG. 57.] [Illustration: FIG. 58.] _MM. Dutertre and Gouault’s System._--One of the most ingenious solutions of the problem of making the telephone call has recently been proposed by MM. Dutertre and Gouault. Figs. 57 and 58 represent the opposite faces of the instrument. It consists of a kind of snuff-box telephone, like the one shown in fig. 26, and it is so arranged as to send or receive the call, according to the way in which it is placed on its stand, which is only an ordinary bracket fastened to the wall. When it is placed on the bracket so as to have the telephone mouthpiece on the outside, it is adapted for receiving, and can then give the call. When, on the other hand, its position on the bracket is reversed, it permits the other station to make the call, by producing vibrations on a vibrator under the influence of a battery, and these vibrations reverberate in the corresponding instrument with sufficient force to produce the call. If the instrument is taken up, and the finger is placed on a small spring button, it may then be used as an ordinary telephone.