The telephone test indicates whether the circuit closer is in position or not, the shot, &c., within the telephone being shaken about by the movement of the buoyant circuit closer, the noise so created is readily distinguished by the receiving telephone at the station. Another form of submarine mine is that known as the "Electro Mechanical" mine. The difference between this form and an ordinary mechanical mine is, that the exploding agent is electricity, and that it may be converted into an electro contact mine if desirable. _Description of a Russian Electro._--The electro mechanical mine, used by the Russians during the late Turco-Russian war, is shown in elevation and section at Figs. 62 and 63. _Mechanical Submarine Mine, used by them during the late Turco-Russian War._--_A_ is the conical shaped case; _B_ the loading hole; _C_ the base plug; _D_, _D_, &c., are five horns, screwed into the head of the case _A_; these are composed of a glass tube _A_, containing a chlorate of potash mixture, enclosed in a lead tube _B_, over which is screwed a brass safety cylinder _C_; when ready for action this latter tube _C_ is removed; directly beneath each of the horns _A_, on the inside of the case, as at _E_, is a thin brass cylinder, closed at one end by a piece of wood _d_, and containing several pieces of zinc and carbon, arranged in the form of a battery, the zinc and carbon wires _z_ and _x_ being led through the piece of wood _d_; _F_ is a copper cylinder containing the priming charge of gun-cotton _g_, and detonating fuse _f_; the terminals of the fuze are connected to two insulated wires, _w_ and _w__{1}, the former of which is led direct to the loading hole _B_, and attached on the inside to the five zinc connecting wires _z_, &c.; the latter is attached to one end of a safety arrangement _S_, the other end of which is connected to the wire _w__{2}, which is attached on the inside to the carbon wires _x_, &c.; the safety arrangement _S_ consists of an ebonite cylinder, containing a brass spiral spring fixed to one end of it, and pressing against a brass plate at the other, thus preserving a metallic connection between the wires _w__{1}, and _w__{2}; the mine is rendered inactive by pressing the spring down, and inserting a piece of ebonite between it and the plate. _Its Action._--The action of this form of electro mechanical submarine mine is very simple; the brass safety cylinders _c_, _c_, &c., being removed on a vessel striking either of the horns, _D_, _D_, &c., the lead tube _b_ is bent, causing the glass tube _a_ to be broken, and the mixture contained therein to flow into the cylinder _E_, instantly generating a current of electricity in the zinc carbon battery, and exploding the mine.