The fact should also be recalled that Dr. Herz had, from his first
experiments, recognized the efficiency of those microphonic contacts
that are obtained by the superposition of carbon disks or other
semi-conducting substances. He has employed these under different
arrangements and with very diverse groupings, but, as a general thing,
it has been the horizontal arrangement which has given him the best
effects.
Let us suppose, then, that four systems of contacts of this nature are
arranged at the four corners of an ebonite plate, C C (Figs. 1 and 2),
at A, A?, B, B?, 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, A?, B,
B?, 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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