Improvements relating to Electric Telegraphy.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements relating to Electric Telegraphy.
We, OLIVER JOSEPH LODGE, of 2, Grove Park, Liverpool, in the County of
Lancaster, D.Sc., F.R.S., Professor of Physics in the University College, Liver-
pool aforesaid, and ALEXANDER MUIRHEAD, of Princes Street, in the City of
Westminster, D.Sc., Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
Our invention relates to systems of telegraphing by means of Hertzian waves
and has for its objects to provide means whereby greater certainty of action is
obtained and whereby the distance between the emitting and receiving apparatus
may be materially increased; to effect, as compared with the systems of telegraphy
at present in vogue, an economy in signalling between distant points, and generally
to effect the improvements hereinafter indicated.
In carrying out our invention we use in the receiving circuiti a recording
telegraph instrument of the Kelvin siphon recorder or other suitable type con-
nected in series with a battery and a coherer of novel construction.
The coherer may be constructed of two or more tubes containing iron or nickel
filings or the like, amalgamated or not, joined up in multiple arc and in conjunc-
tion with these tubes is a vibrating hammer which is kept in constant motion,
preferably by means of clockwork, and is so placed relatively to the tubes of filings
that it comes into contact with each tube successively during every period of
revolution.
The construction of the coherer may be such that decohesion or the restoration
to sensitiveness of the mass, which forms the active part of the coherer after every
passage of the Hertzian waves, takes place in the mass itself instantly after the
act of cohesion, without the aid of vibrating hammers or similar devices, that is to
say, in one form of coherer made according to this invention the filings form a
conducting mass spread out on a strip or otherwise supported in the magnetic⚫
field between the two poles of either a permanent magnet or an electromagnet so
that on the passage of Hertzian waves through the filings, when electrical cohesion
or more complete contact has taken place under the electrical stimulus of such
waves, a stronger current from the battery in connection with the coherer flows
through the strip or mass of filings, the result being a greater deflection of the
mass due to the action of the magnetic field. The bending or deflection in one
direction of the strip carrying the filings or the disturbance of the mass of filings
separates them and thus breaks down the cohesion between them.
For the transmitter we may employ an ordinary extra current spark such as
occurs when the current of a voltaic battery is broken or when a current round
a self-induction coil is varied, or started, or stopped, or when a condenser is charged
or discharged, or any other means of producing an electric jerk or discontinuous
or transient current such as are capable of exciting a coherer. And the effect of
these electric jerks may be conveyed to the distant coherer either through space
or along conductors of any kind, or along bare wires, or the outer sheathing of

page_text: cables, or any other conductor leading from the sending station to the receiving
station.
As an example of a complete telegraphic system according to this invention we may
specify the following: -At each end of an uninsulated metallic wire or conductor
between two stations there will be any form of coherer, such for example as those
above described, in circuit with a battery and a recording instrument, one terminal
of the coherer being connected to the telegraph wire, or conductor, and at the
same point is connected through a self-induction coil, a Morse key and battery,
one pole of the latter being to Earth. Sometimes we may connect a condenser
between the earth and the terminal of the coherer opposite to that which is con-
nected to the telegraph wire or conductor to increase the effect of the arriving
electrical impulse upon the coherer.
When we employ synchronous collectors or resonators in conjunction with our
system of telegraphy we in some cases connect the coherer to the extreme end of
the resonator when a single resonator is used, or when a pair of equal resonators
is used end to end, we place the coherer between the two inner knobs of the dis-
charger and between the coherer and battery and receiving instrument respectively
a pair of self-induction coils to isolate the coherer for oscillations.
Another arrangement is with a closed circuit similar to one of Hertz's arrange
ments in which little sparks occurred between the discharger knobs.
At that same
place we put the coherer together with its battery and receiving instrument, but
to avoid the disturbance of time period caused by the arrangement, we introduce
a condenser across the poles of the coherer of sufficient capacity to act as a virtual
short-circuit for oscillatory currents. The addition of a condenser to any simple
coherer circuit across the poles of the coherer eliminates battery and receiving
instrument so far as oscillations are concerned and at the same time it gives a
static charge ready to strengthen the surgings through the coherer. This use of a
condenser in coherer circuits such as will enable them to have a definite time
period in spite of their containing also a battery and recorder or galvanometer or
other complications of coils, and the like, forms a distinct part of our invention.
A convenient arrangement of adjusting the sensibility of the coherer circuit is to
place the colerer in one arm of a Wheatstone bridge arrangement so that the
receiving instrument responds whenever the coherer changes in resistance. An
electromagnet may be placed in another arm of the Wheatstone bridge arrange-
ment so that whenever the coherer diminishes in resistance through the influence
of electric waves the electromagnet loses much of its force and so can drop a keeper
on to the coherer to tap it back. The electromagnet holds the keeper on until the
change in coherer resistance drops it off without any tendency to "tremble." The
electromotive force applied to the coherer can in the above arrangement be adjusted
to any fraction of the battery employed.
With coherers constructed as above described we sometimes arrange the receiving
circuit as follows:-In three parallel circuits we join up (1) a battery and
adjustable resistance (2) a condenser and recorder and (3) the coherer of variable
resistance. Or we substitute an induction coil for the condenser joining the
coherer, the battery and the primary of the induction coil in series and inserting
the receiving instrument in the secondary. By the above arrangements of
apparatus in the receiving or colerer circuit fluctuations of current are detected
in the receiving instrument rather than the current itself.
A. F. SPOONER,
323, High Holborn, London,
Agent for the Applicants.

page_text: We, OLIVER JOSEPH LODGE, of 2, Grove Park, Liverpool, in the County of
Lancaster, D.Sc., F.R.S., Professor of l'hysics in University College Liver-
pool aforesaid, and ALEXANDER MUIRHEAD, of Princes Street, in the City of
Westminster, D.Sc., 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:—
Our invention relates to systems of telegraphing by means of Hertzian waves and
has for its objects to provide means whereby greater certainty of action is obtained
and whereby the distance between the emitting and receiving apparatus may be
materially increased; to effect, as compared with the systems of telegraphy at
present in vogue, an economy in signalling between distance points, and generally
to effect the improvements hereinafter indicated.
In carrying out our invention we use in the receiving circuit a recording or
receiving instrument as indicated at a in the accompanying drawings connected in
series with a battery band a coherer c of the construction hereinafter described or
other suitable form. The receiving instrument a shown in the diagrams is a
Kelvin siphon recorder but it may be a telephone or other instrument able to
respond to slight fluctuations of current.
The coherer, which may be of any suitable construction, is indicated diagram-
matically in most of the accompanying drawings as being of that form now known
as a single-point coherer. According to our present invention, however, two or
more coherers are employed (the diagram Figure 1 shows three) joined up in mul-
tiple are and in conjunction with them is a rotating or vibrating tapper or cam d
which is kept in constant motion, preferably by means of clockwork, and is so placed
relatively to the said coherers that it comes into contact with each one successively
during every period or revolution. The object of this arrangement is to ensure
that at least one coherer shall be in its receptive condition.
The construction of the coherer may be such that decohesion or the restoration
to sensitiveness of its active part after every passage of the Hertzian waves takes
place in the sensitive part itself instantly after the act of cohesion, without the aid
of vibrating hammers or similar devices. Figure 2 illustrates this form of coherer.
Suitable filings e forming a conducting mass are spread out on a flexible light
strip f. This strip is suitably supported in the magnetic field between the two
poles NS of either a permanent magnet or an electromagnet. When the strip
is made of aluminium or other suitable metal there is placed between it and the
filings an insulating film fl of varnish or other material. It will be seen that at
one end of the strip f the filings extend beyond the insulating film f¹ whilst at the
other end the latter effectually separates the filings from such strip. A second
smaller light metallic strip g is maintained by light springs g upon the filings e.
When, under the stimulus of Hertzian waves, electrical cohesion or more complete
contact takes place, a stronger current from the battery b flows through the whole
length of the strip f to the mass of filings and thence through the upper strip g
to complete the electrical circuit; the result being a greater deflection of the strip
due to the action of the magnetic field. The bending or deflection in one direc-
tion of the strip f disturbs the mass of filings and separates them thus breaking
down the cohesion previously existing between them. The coherer may be con-
fined within any suitable casing.
As transmitter we may employ (as shown in Figure 3) an ordinary extra
current spark such as occurs when the current of a voltaic battery 61 is broken or
when a current round a self-induction coil his varied, or started, or stopped, or any

page_text: other means of producing an electric jerk or discontinuous or transient current
such as are capable of exciting a coherer but we prefer to use, as illustrated in
Figure 4, an induction coil i with one or more spark gaps j joined up as shown.
And the effect of these electric jerks may be conveyed to the distant coherer either
through space or along conductors of any kind, or along bare wires such as k or
the outer sheathing of cables, or any other good bare conductor leading from the
sending station to the receiving station.
As an example of a complete telegraphic system according to this invention we
may specify the following -At each end of a bare or uninsulated metallic wire
or conductor k, extending between any two stations, is one or more coherers c in
circuit with a battery band a receiving or recording instrument a, one terminal of
the coherer being connected to the telegraph wire or conductor k, and at the same
point connected through a switch is a self-induction coil or its equivalent, a
Morse key m and battery 61; one pole of which latter may go to Earth as indicated
in Figure 3 or else to some lofty capacity like a lead roof.
Sometimes we may connect a condenser n between the earth and the terminal
of the coherer opposite to that which is connected to the telegraph wire or con-
ductor to increase the effect of the arriving electrical impulse upon the coherer also
as shown in Figure 3.
When we employ synchronous collectors or resonators in conjunction with our
system of telegraphy we in some cases connect the coherer to the extreme end of the
resonator, when a single resonator is used, as illustrated in Figure 5; or when a
pair of equal resonators is used end to end, we place the coherer between the inner
ends of the resonators as shown in Figure 6. In this arrangement the battery and
receiving instrument connexions if made to the resonator at all are made at the
middle of the resonators otherwise they would disturb the oscillation period. The
coherer being a non-conductor normally does not disturb the resonators.
Another arrangement, as shown in Figure 7, is with a large closed circuit
similar to one of Hertz's arrangements in which little sparks occurred between the
discharger knobs. At that same place we put the coherer c and in another part of
the circuit we place the battery band receiving instrument a but to avoid the dis-
turbance of time period caused by their introduction we shunt them by means of
a condenser n of sufficient capacity to act as a virtual short-circuit for oscillatorý
currents.
The addition of a condenser as a shunt to any simple coherer circuit in this
manur eliminates battery and receiving instrument so far as oscillations are
concerned. This use of a condenser in coherer circuits such as will enable them
to have a definite time period in spite of their containing also a battery and
recorder or telephone or other complications of coils and the like forms a distinct
part of our invention.
A convenient arrangement of adjusting the sensibility of the coherer circuit is
to place the coherer c, as shown in Figure 8, in one arm of a Wheatstone bridge
arrangement so that the receiving instrument a responds whenever the coherer
changes in resistance. An electromagnet p may be placed in another arm of the
Wheatstone bridge arrangement so that whenever the coherer diminishes in
resistance through the influence of electric stimulus the electromagnet loses much
of its force and so can drop a keeper pon to the coherer to tap it back. The
electromagnet p holds the keeper on until the change in coherer resistance causes it
to drop off without any tendency to "tremble." The electro-motive force applied
to the coherer can, in the above arrangement, be adjusted to any fraction of the
battery employed. The coherer shown in Figure 8 is a known kind consisting of a
tube of metallic or other filings or powder but obviously any other form may be
employed.
As shown in Figure 4 the receiving devices may be arranged in three parallel
circuits that is to say (1) a battery b and adjustable resistance g (2) a condenser n
and recorder or other receiving instrument a and (3) the coherer_c.
Or we may,
as shown in Figure 9, substitute an induction coil P.S. for the condenser n, joining

page_text: the coherer c, the battery b, and the primary P of the induction coil in series
and inserting the receiving instrument a in the secondary S. By the above
arrangements of apparatus in the receiving or coherer circuit fluctuations of current
are detected in the receiving instrument rather than the mere presence itself of
a current.
Of the various alternatives herein before mentioned the method we at present
prefer is a spark gap at the sending end of the system excited by a Ruhmkorff coil
with a bare wire or mere earth connection leading to a coherer at the receiving end,
the other terminal of the spark gap and of the coherer respectively being each
connected to one of a pair of elevated conductors or "sky-plates" such, for instance,
as a pair of insulated roofs. The diagram Figure 10 illustrates this arrangement.
r, depict respectively the sending and receiving sky-plates. j is the spark gap
and c is the coherer. The dotted connections s,. s lead to the Ruhmkorff coil,
transmitting key and battery, whilst the similar connections s¹, s¹ lead. to the
remaining elements of the coherer circuit. k represents a bare wire, conducting
pipes, or the like. Or instead of sky plates as shewn in Figure 10 other earth
plates may be employed or there may be two bare wires instead of one between
the two stations as hereinafter described. If the bare wire has to stop anywhere
each end should be terminated by a large flat area.
A complete station would as before explained also contain a switch for changing
it over from sending to receiving. The function of the switch in the arrangements
is explained by reference to the diagram Figure 11. is the sky plate and E the
earth or bare wire connection. For sending, 1 and 6 and 5 and 4 are connected
and 2 and 3 for safety to the coherer thereby short-circuiting it. For receiving,
1 and 2 and 3 and 4 are connected and optionally 5 and 6.
The sky-plate instead of being a mere emitter or collector may be a syntonic
radiator or resonator as shown in Figure 12 everything else remaining the same
as in Figure 11. In Figure 12 the oscillations sympathetically set up in the
resonator overflow into the coherer as soon as they have become strong enough, by
reason of sympathetic tuning or resonance.
Sometimes we employ two earthed connections or partially insulated wires and
in that case, as shown in Figure 13, we connect the transmitting coil to two spark
gaps j, j (either of which may be closed at pleasure) leading to the two wires, k, k,
and the coherer circuit at the distant end, either in series or in shunt with its
battery and detector to the other ends of the two wires. When battery and detector
are joined in series with the coherer a condenser shunting them is useful as in
former diagrams.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
1. In combination, in the receiving circuit of a system of Hertzian wave tele-
graphy, two or more coherers joined up in multiple arc and means whereby such
coherers are successively decohered substantially as set forth.
2. The coherer constructed substantially as described with reference to Figure 2
of the accompanying drawings.
3. A telegraphic system comprising one or more bare or uninsulated metallic
wires or conductors between the stations, means for transmitting electric jerks or
discontinuous or transient currents such as are capable of exciting a coherer into
the conductor, and a coherer circuit substantially as set forth.
4. In a coherer circuit the condenser n or its equivalent located substantially
as and for the purpose set forth.
5. Coherer circuits constructed as described with reference to Figures 5, 6 and 7
of the accompanying drawings.
6. A coherer circuit comprising a Wheatstone bridge arrangement in one arm
of which is the coherer and in another arm of which is an electromagnet which
latter effects the decohesion of the coherer substantially as set forth.

page_text: 7. At the receiving end of a telegraphic system three parallel circuits consisting
respectively of a battery and adjustable resistance, a receiving instrument and a
condenser or its equivalent, and a coherer.
8. In a coherer circuit, means, substantially as set forth, whereby fluctuations of
current therein are detected and recorded.
Dated this 10th day of June 180Q