Year: 1899

page_text: LESLIE BRADLEY MILLER, of 93, Hatton Garden, London, Manufacturing
Electrician, do hereby declare the nature of this invention to be as follows;-
-
My improvements relate to the receiving apparatus used in wireless tele-
graphy and my aim has been to obtain greater speed of signalling and increased
sensitiveness.
My coherer is attached to the light armature of a small and very quick
acting electro magnet either directly or by a piece of spring metal. The electro
magnet, which serves as a Morse sounder as well as for decohering, is thrown
into action by the relay and the sudden jerk forward of the armature serves to
effectually decohere the filings. I have however found that the speed of
decohering is greatly increased if the movement of the armature away from a
stop is made to break the coherer circuit. In addition the relay can be more
delicately adjusted when this is done, and when the shunt circuit through the
relay is open the received wave can only pass through the coherer.
Instead of an electro magnet a solenoid may be used to decohere.
piece of iron is attached to the coherer and the circuit through it is made and
broken by its own up and down movement.
A small
The coherer filings should be of a metal or alloy that cannot be magnetised
owing to proximity to the electro magnet and the coherer itself so constructed
that it can be exhausted and sealed with the least possible chance of its sensi-
tiveness being impaired by the hot blast of the glass blower. I attain this by
fusing into the bottom of a glass tube the two platinum wires attached to the
lower portion of two metal electrodes insulated from one another, then cleaning
the acting surface from the open end of the tube, inserting the filings, then
a plug or screw and finally exhausting and sealing up the open end.
An ordinary Morse local inker can be attached in parallel to the decohering
magnet, or an electro chemical recorder may be used in order to avoid self
induction.
171 J f 1900

page_text: the same is to be performed, to be particularly described and ascertained in
and by the following statement: —
My improvements relate to the receiving apparatus used in wireless telegraphy.
The coherer is fixed at the end of the armature of an electro magnet, placed
in the local circuit of the relay, and hereinafter called the decoherer.
An ordinary horse shoe electro magnet may be employed for vibrating the
coherer, with a make and break contact arranged at the back of the armature,
but this must not be in the circuit of the wire on the magnet but in the
coherer circuit..
The break may also be effected by another small armature worked by the
same magnet or by an entirely separate magnet in series or parallel with the
other. Instead of the break being complete, it may be shunted with a resis-
tance or self induction, wound on the relay or separately, and if a relay be
used in which a central tongue plays -between two contacts, one side may be
used for the local circuit, and the other for adding to the coherer circuit_a
resistance or self induction that is short circuited till the contacts open.. In
a relay used in this way the coherer contact should however preferably be
insulated from the tongue.
It is of importance that all harmful self inductive effects in the decoherer
or relay should be reduced as much as possible by the ordinary methods used
in telegraphic apparatus, and to prevent any excessive rebound or shock in
the case where the contact is on the armature, and the latter flies back to
complete the local circuit, the contact should preferably be fixed on a small
spring or a block of india rubber.
It is evident that many forms of electro magnet may be used for decohering,
or a solenoid may lift the coherer off a contact or contacts, and let it fall
again.
The coherer I prefer to employ in connection with the decoherer above
described is used in a vertical position and consists of two contacts, concentric,
or semi circular, of metal or carbon insulated from one another with glass or
mica. Platinum wires are attached to the bottom of these after which the
whole coherer is inserted into a glass tube and the glass at the bottom fused
round the platinum electrodes. The surface of the metal is then carefully
cleaned from the open end of the tube, a suitable quantity of metal or carbon
dust shaken in and the whole tube exhausted and sealed up. In order to prevent
any oxide or sulphide being formed on the acting surfaces during this operation,
I find it advisable to protect the filings from the heat by enclosing them in a
metal tube which may form one of the electrodes, or the surface may be protected
by a layer of sand while the glass is being drawn to a capillary tube, which
sand can afterwards be replaced by the proper metal dust or filings. In order
that the coherers may readily be changed they can be fitted with the Edison
screw cap or any other attachment used for incandescent lamps and their
holders.
It should be understood that although I prefer the type of coherer above
described any small, light coherer may be decohered by the same method, pro-
vided that if magnetic metals are employed they must not be placed too near
the magnet.
Referring to the drawings, in Fig. A, A, is the electro magnet, B the
armature carrying the colerer C. The contact at E is in the coherer circuit.
Fig. 6 is a diagram showing the usual mode of connecting the circuits in
the receiving apparatus the instruments shown in addition to those mentioned
being the relay R, and the Morse inker M with the winding on the two limbs
of each in parallel and in parallel with one another. It must be understood
that any make and break contact or electro magnet may be shunted and that
the coherer may be in the secondary circuit of a transformer.
Fig. 2 shows a vertical and horizontal section through the concentric form
of my coherer that I have found to give the best results. In this the filings

page_text: are enclosed within an outer metal tube which forms one electrode, and rest
on the surface of an inner electrode separated by a glass ring from the outer.
Figs. 3, 4, & 5 are sections through a form of coherer in which the contacts
are semi circular except for the narrow piece of insulation between them.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. In a receiver for wireless telegraphy the method of decohering substan-
tially as described, and shown in Figs. 1 & 6.
2. The combination of a decoherer substantially as described and shown in
the drawing Fig. 1 with a coherer substantially as described, and shown in
Figs. 3, 4 & 5.
3. The coherers substantially as described, and shown in Figs. 3, 4, & 5.
Dated this 13th day of February 1900
LESLIE B. MILLER.