The connections of the wires are made as follows:—
The line wire w is led through the base of the apparatus and connected to a piece of brass under the ebonite support l, in connection with one of the wires of the bobbin m, the other wire of which is attached to the metal strip s; the wires of the bobbin m1 are connected, the one to the metal strip s1, the other to a piece of brass under the ebonite support l; from this latter piece of brass a wire w1 is led to the brass screw x. The wires w2, w3, from the fuzes are led, the one to the brass screw x, the other to a screw y, which forms through the metal of the apparatus the earth plate. One of the wires of the telephone t is connected to the brass screw x, the other w4 is connected to the piece of brass to which the line wire w is also attached. While the circuit closer remains in a state of rest, the current from the signalling battery flows along the line wire w, up the telephone wire w4, through the telephone which has a high resistance, then by the wire w2 through the fuzes, and to earth by the wire w3.
On the circuit closer being struck, by which cause the armature n is brought up to the cores of the bobbins m, m1, and the piece of brass r in contact with the metal strips s, s1, the signalling current, instead of circulating through the high resistance of the telephone t, passes round the bobbin m, down the metal strip s, across the brass piece r, up the metal strip s1, round the bobbin m1 (thus forming an electro magnet of m, m1), and by the wire w, direct through the fuzes to earth, and so explodes the torpedo. The effect of the telephone resistance being cut out, is to strengthen the signalling current, and enable it to work the shutter apparatus and so throw the firing battery in circuit and explode the mine.
The advantages of this circuit closing apparatus are:—
1.—Simplicity.
2.—Compactness.
3.—Increased certainty of action, due to the sustained contact of the armature n, on the apparatus being struck.
4.—Additional means of testing a system of electrical submarine mines, which is afforded by the telephone:—