Let us suppose, then, that four systems of contacts of this nature are arranged at the four corners of an ebonite plate, C C , at A, A¹, B, B¹, and that they are connected with each other, as shown in the cuts—that is to say, the upper disks, e, f, g, h, parallel with the sides of the plate, and the lower disks, A, A¹, B, B¹, diagonally. Let us admit, further, that the plate pivots about an axis, R; that the disks are traversed by small pins fixed in the plate; and that small leaden disks rest upon the upper disks. Finally, let us imagine that the plate is connected at one end, through a rod T, with a telephone diaphragm. Now it will be readily understood that the vibrations produced by the diaphragm will cause the oscillation of the plate, C C, and that there will result therefrom, on the part of the disks, two effects that will succeed one another.

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