Year: 1897

page_text: LESLIE BRADLEY MILLER, of 2, Grays Inn Road, London, Electrical Engineer, do
hereby declare the nature of this invention to be as follows:-
My improvements relate to instruments known as coherers, and the methods of
decohering the same.
I stretch or suspend the coherer on a strained wire or string and cause the
armature of an electro magnet acting against a spring to pull a piece of metal
having a serrated edge across the wire like the bow of a fiddle over the strings.
This effectually shakes up the filings. The wire should preferably form part of
the circuit through the coherer and a suitable form of coherer I have devised con-
sists of an ebonite cup with four small holes in the side. A piece of wire is passed
through the two holes and a knot made, then a similar wire is passed through the
other two holes from the other side. Looking into the cup from above there are
two parallel wires lying close to the bottom, and one wire coming from each side to
posts made so that the wire can be strained a little. A pinch of filings is thrown
on the wires. Instead of one wire several stretched wires may be used. The
advantage of the fiddle bow method compared with tapping, is that the whole
motion to and fro tends to decohere, but the strained wire suspension is advan-
tageous also in the case of tapping. Another suitable form of coherer consists of
a strained wire passing through a tube lengthwise the wire being one electrode
and the tube the other.
Referring to the cup form of coherer, in order to decohere, the filings may be
lifted bodily if they are of magnetic material such as nickel or iron by the pole
of a magnet, dipping into the cup or they may rest on a sort of turn table made
to revolve by an electro magnet when the relay comes into action.
Instead of using the armature of an electro magnet to work the fiddle bow
decoherer, or to give small blows, the expansion and contraction of a wire carrying
a current sufficient to heat it may be utilized.
LESLIE BRADLEY MILLER, of 2, Grays Inn Road, London, Electrical Engineer, do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
My improvements relate to the receiving instruments used, in Hertzian wave
telegraphy, known as coherers, and especially to methods of decohering the same.

page_text: In one form of receiver, the coherer, which may be of any suitable form, is
carried on a wire stretched between two posts. Resting on the wire there is a
small brass rod which has a screw thread cut on its surface, or it is otherwise
roughened. This rod is pivotted at its further end to an insulated prolongation of
the armature of an electro magnet. The coherer is in circuit with one cell and the
winding of a sensitive relay, with the bell winding in the local circuit. When
the bell armature is attracted the milled rod is drawn over the taut wire like the
bow of a fiddle over the strings till the resulting agitation of the filings decoheres
them, the decohering action being augmented by the knock which the wire re-
ceives from the stop on the rebound of the armature, or if the scratcher fails to act,
by the further stop.
Referring to the drawing in Fig. 1, A, A, is the taut wire, B, the coherer, C,
the milled rod. This rod is pivotted at its further end, and gives signals on a
suitably placed gong. D, D, are two milled nuts holding between them a horse
shoe shaped piece of brass E, which slides on the milled rod and serves the purpose
of keeping the nuts from becoming loose as well as holding in the wire A. Fig. 2
is a side view of the decoherer. It will be seen that in this method of decohering
the whole to and fro motion of the armature is utilized.
The coherer I prefer is that shown in Fig. 1, in which two wires are taken
parallel across the bottom of a small ebonite or glass cup suitably sealed up, the
filings being preferably confined to the space between, the wires by placing the
latter at the bottom of a wedge shaped cutting. Instead of connecting the two
sides of the coherer to wings, or to a vertical wire and earth, a third wire lying
between the two shown in the drawing of the coherer and not forming part of
the circuit may be employed. This can be connected to earth, the other two sides
of the coherer being connected to separate horizontal or vertical collecting wires
or wings, or these connections may be reversed.
Fig. 3, shows another form of coherer in which a central wire, with or without
a disc attached, forms one electrode, and the metal containing tube the other. If
the central wire be cut the outside tube can be used as the idle pole to connect
to earth or otherwise as described in the case of the parallel wire coherer.
Instead of decohering by shaking or knocking the filings they may be caused
to revolve relatively to one or both electrodes.
Fig. 4, shows a cup shaped decoherer A made of metal and forming one electrode.
This contains filings into which the other electrode B projects, being attached to
the point of an insulated screw B. The coherer can revolve on the two screws
and this can be conveniently effected by such an electro magnet as the one shown
in Fig. 5, which is thrown into action by the relay. The coherer can be fitted with
teeth and a click if it be desirable that At should revolve always in one direction.or
it may be made of magnetic metal so that the armature holds on to it when
magnetised but not otherwise. It is evident that the coherer can revolve vertically
or horizontally and that the same method of decohering can be applied to Fig. 3,
or any similar shaped coherer by making sliding contacts on to the two electrodes.
In order to avoid the sparking due to self induction the expansion of a hot wire
may be employed to effect decolering, as shown in Fig. 6. When this is thrown
into action by the relay it expands and this can be used to cause a coherer to
revolve by means of the friction of an, attached wire on the surface of a coherer as
shown in the drawing, or to shake up the filings in the same way as an electro
magnet would do.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is: :-
1. In a receiver for Hertzian waves the method of sustaining the coherer on a
stretched wire and decohering by setting the wire in vibration substantially in
the manner described, and shown in Figs. 1. 2 & 3.

page_text: 2. In a receiver for Hertzian waves the method of decohering by causing the
powder, or one or both of the electrodes in the coherer to revolve, substantially as
described, and shown in Figs. 4 & 5.
3. In a receiver for Hertzian waves the method of making use of the expansion
of a wire heated by an electric current to effect the decohering substantially as
described, and shown in Fig. 6.
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