Improvements in Syntonic Telegraphy.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Syntonic Telegraphy.
We, OLIVER JOSEPH LODGE, of 2, Grove Park, Liverpool, in the County of
Lancaster, D.Sc., F.R.S., Professor of Physics in University College, Liverpool,
aforesaid, and ALEXANDER MUIRHEAD, of Princes Street, in the City of West-
minster, D.Sc., Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
Our invention relates to improvements in the receiving circuit of a system of
syntonic telegraphy based on the employment of Hertzian waves, whereby the
coherer is rendered more sensitive to the influence of the Hertzian waves instead
of being shunted or otherwise interfered with by its battery and by the coils of
the receiving instrument in connection with it. Our invention further relatos
to improvements in connection with the protection of a coherer from impulses
not intended to reach it, and to the other improvements hereinafter indicated.
In carrying out the first part of uur invention a condenser of largo capacity is
interposed in the middle of a syutonic receiver, between one of the capacity areas and
In that position
the self inductance coil connected up to the other capacity area.
the condenser barely affects the period, and in no way injures the syntonic
accumulation of oscillations in the receiver. The coherer is connected to the
capacity areas as usual, so as to receive the full benefit of their accumulated
impulse. The circuit containing the battery and the receiving instrument is
joined to the two terminals of the condenser; in which position the battery is
incapable of producing any steady current, except through the usually high
resistance of the coherer, and its circuit does not effectively shunt the coherer,
since so far as oscillations are concerned it is itself short circuited by the condenser.
as if no battery circuit were there; the battery and telegraph instrument (as in
former arrangements) being nevertheless there all the time, ready to display
every fluctuation in the coherer's resistance.
Or, instead of a simple battery circuit, a Wheatstone bridge system of con-
nexions is equally feasible, the condenser (with coherer) constituting as it were
gne arm of the bridge, and the telegraphic instrument being in the bridge wire.
Another plan of connexions is one in which the condenser, instead of being
introduced in the syntonic region between the capacity areas, is placed in the coherer
circuit, and is itself shunted by the battery and the circuit of the receiving
instrument, or by a Wheatstone bridge system, whose resistances are in this case
preferably inductively wound.
This plan is almost as effective as the previous one because steady currents from
the battery must pass through the coherer, ignoring the condenser, while alterna-
tions from the receiver also act freely on the coherer, through the condenser,
ignoring the receiving instrument.
An alternative plan is to use the condenser to shunt the telegraphic receiving

page_text: instrument alone, so as to avoid the retarding effect of its self induction on feeble
oscillations proceeding towards the coherer.
Sometimes in arranging the coherer circuit so that the coherer shall receive
unshunted the whole of the impulse from a receiver or collector, we employ in
connection therewith a revolving switch designed to alternately connect the
coherer) with the capacity areas or syntonic receiver, so as to be cohered;
(b) with the battery and telegraph circuit, so as to display or record an effect due
to this coherence; (c) to break cohrrer connection and close a local circuit which
shall cause a mechanical tap or other suitable tremor, so as to produce deco-
herence or, (as an alternative to (c)) () instead of mechanical tapping-back,
it is possible to restore a coherer to sensitiveness in a very definite manner
if it be arranged to receive an impulse from an electric wave while it is connected
to a battery circuit. Hence instead of the process stated as (c) the commutator
may be arranged so as to momentarily connect the coherer with the receiver while
the coherer is still connected to the battery and telegraph circuit, or while con-
nected to a special or extra battery circuit without any receiving instrument in
it and in that case if the impulse is strong enough it will be knocked back, not
so completely as if tapped, but sufficiently, and always into a position of con-
siderable sensitiveness. (e) the last operation which the revolving commutator
has to perform is to restore the connexions as in (a) and so permit the cycle to
recur. The commutator may revolve quite rapidly, being only limited by the
quickness of response and recovery of the signalling instrument.
If the impulses coming from a distant station are not sufficient to effect the
decoherence by process () (for a coherer is by no micans as responsive when it
is joined up to a closed circuit as to an open one) then it is easy to make the
revolving commutator, while in position (d) also excite momentarily a local small
weak emitter, which shall have the desired restoring effect independently of the
distant signals; but we prefer the mechanical method of tapping-back of (c).
Thus (to summarise) in position (a) of the revolving commutator the coherer is
ready to receive all suitably syntonised arriving waves; in position (b) it enables
them to be recorded; in position (c) it will become partially decohered or restored
to its sensitive state, and then position (a) will recur.
A coherer is sensitive not only to the desired impulse arriving from a distance
and collected by the appropriate receiver, but it is also liable to respond to any
local sparks or electric surgings in its neighbourhood, especially to oscillations
in the adjacent sender; but it may be protected from all these by complete
enclosure in a flawless metallic box.
For the purpose of protecting the coherer from undesired disturbance, there-
fore, we enclose it, (sometimes together with all coils wires batteries &c.,
connected to it), in a metallic covering or case, leaving only round holes or short
tubes for the collector terminals to enter by, and for vision or any other needful
purpose requiring an aperture. For through round holes of moderate size larġo
electric waves do not readily pass, whereas through chinks or long slits, no
matter how infinitely narrow, they can pass with ease.
They likewise pass in by means of any insulated wire which enters the box, no
matter how short it may be, but through any wire which is thoroughly joined to
the metal wall of the box where it enters, the waves cannot pass.
Hence it is not absolutely necessary to remove the terminals from their aper-
tures, when they are not being used for the purpose of establishing communica-
tious and enabling waves from the receiver to enter the box aud reach the coherer:
for these samo terminals may, when they are raised, completely plug with metallic
continuity the small holes through which they can freely afterwards be lowered.
The only part of the coherer or detector portion that need be outside the box is
the index of the telegraph instrument employed, which can bo acted upon and
deflected by its coil inside acting magnetically through the metal wall.
When the plan of withdrawing the terminals of the box is adopted it is
sufficient to put the coherer alone in the box.

page_text: Anything protruding through an aperture in the box, except the wire leading
to receiver when joined for "receiving," must either be there joined metallically
up to the walls of the box, or it must be a non-conductor.
In order to use the same identical capacity areas and self inductance coil alter-
nately as emitter and as receiver, we have devised a switch which effects at one
motion the necessary connexions and alterations.
These are:-For preparing to receive waves, (1) close the spark gap between, tho
capacity areas, which can be done by a relay or local-magnet circuit operated by
the switch just mentioned, and (2) bring down the pair of terminals into contact
with the coherer-circuit inside its metal box.
For preparing to emit waves, (1) raise the pair of terminals just mentioned out
of contact with the coherer-circuit, and either plug them tight into holes in the
box-wall, or remove them completely from it: (2) unclose the spark-gap between
the capacity areas by means of the same local magnet circuit; and (3) close the
circuit which connects a Ruhmkorff coil with its battery and with the signalling
key; thus leaving to the latter the final closing and regulation or production of
intelligible signals, by means of sparks supplied to the capacity areas from the
Ruhmkorff.
One end of the switch whose function we have now described is depressed and
left down in its clamp so long as receiving is desired; the other end is depressed
and left down in its clamp so long as sending is desired, i.e. so long as the
separate transmitting key is being worked. The receiving end should be left
down whenever active transmission is not going on.
By the means now described the coherer may be completely isolated, and
will not feel the waves sent out from its own station, while yet, when properly
switched on, it is perfectly sensitive to waves of proper frequency arriving from a
distance.
The signalling key can only be used when the switch is "down" for sending.
At other times the switch is "up" for receiving, the coherer being got at inside
its case by two long pins.
A sensitive coherer should be protected from accidental mechanical shocks
while working. It may therefore be mounted on a mass of considerable inertia
supported in an elastic manner. For instance the metal box containing the
coherer and its circuit may have thick 'walls and be supported on springs inside
an outer metal case. The outer case may enclose the trembler or decoherer and
other accessory mechanism; and it too may be kept usually closed, so that any
holes left in the walls of the inner case are of still less consequence. The tapper
or trembler can be driven electrically if it be mounted outside the inner box, for
then its breaking spark has no deleterious influence.
This 9th day of December 1897
A. F. SPOONER,
323, High Holborn, London, Agent for the Applicants,
COMPLETE SPECIFICATION.
Improvements in Syntonic Telegraphy.
We, OLIVER JOSEPH LODGE, of 2, Grove Park, Liverpool, in the County of
Lancaster, D.Sc., F.R.S., Professor of Physics in University College, Liverpool,
aforesaid, and ALEXANDER MUIRHEAD, of Princes Street, in the City of West-
minster, D.Sc., Electrical Engineer, do hereby declare the nature of this invention

page_text: 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 improvements in the receiving circuit of a system of
ayntonic telegraphy based on the employment of Hertzian waves, whereby the
coherer is rendered more sensitive to the influence of the Hertzian waves, and is no
as hitherto, shunted or otherwise interfered with by its battery and by the coils of
the receiving instrument in connection with it. Our invention further relates
to improvements in connection with the protection of a colerer from impulses
not intended to reach it, and to the other improvements hereinafter indicated.
In carrying out the first part of our invention, and referring first to the
diagram Figure 1, a condenser a of large capacity (that is much larger than that
of the exposed areas or plates b and c) is interposed in the radiating or absorbing
portion of the system that is between the two insulated sheets, cones, or surfaces
of metal b and c constituting the capacity arens, and the self inductance coil d
(preferably adjustable) which together form a syntonic receiver. In that position,
that is to say where the electric energy is kinetic, or let us say in the "
region, the condenser a barely affects the period, and in no way injures the
syntonic accumulation of oscillations in the receiver. The coherer e is con-
nected to the capacity areas as usual, so as to receive the 'full benefit of their
acoumulated impulse. The circuit containing the battery f and the telegraphic or
telephonic receiving instrument g is joined to the two terminals of the con-
denser; in which position the battery is incapable of producing any steady current,
except through the usually high resistance of the coherer, and its circuit does not
effectively shunt the colerer since so far as oscillations are concerned it is itself
short-circuited by the condenser.
current
"
The condenser may be compactly stowed away as if part of one of the capacity
Brens. The coherere may be of any known or convenient form; either single-
point or multiple-point, or filings-tube, or any other form of metallic microphone,
adapted, by the varying resistance of its contacts, to act as detector of electric
oscillations which are excited in the syntonic receiver by the arrival of Hertz
waves of appropriate frequency.
A modification is shown in Figure 2, wherein is a syntonic receiver with one of
its capacity areas uninsulated, that is to say consisting of the earth. The capacity
area is an elevated metal area communicating with the coil d by a metal ribbon
or rod h after the manner of a lightning conductor, but of the highest con
ductivity copper. Similarly the conductor h' leading down to the earth is of
high conductance and preferably of ribbon so as to offer considerable surface to the
current. Substantial earth connexion may be made in any of the well known
ways; or the conductor may actually lead all or part of the way underground
to the distant station.
By the insertion of a condenser as thus shown the coherer can pick up dis-
turbances from a syntonic receiver as if no battery circuit were there; the battery
and telegraph instrument (as in former arrangements) being nevertheless there all
the time, ready to display every fluctuation in the coherer's resistance.
Or, instead of a simple battery circuit, a Wheatstone bridge system of connexions
is equally feasible, the condenser (with coherer) constituting as it were one armi
of the bridge, and the telegraphic or like receiving instrument being in the bridge
wire. Such a device is illustrated in Figure 3 wherein the simple battery circuit
of Figures 1 and 2 is replaced by the Wheatstone bridge connexions with the
coherer e as the fourth resistance whose fluctuations enable the battery f to act on
the signalling instrument g. A siphon recorder in the position shown in the
figure will now give positive or negative deflections according as the resistance
of the coherer e increases or decreases with successive stimuli; whereas with the
simple circuit the deflections are all on one side of zero.
Another plan of connexions applicable to any form of syntonic receiver is one 5
in which the condenser, instead of being introduced in the ayntonic region between

page_text: the capacity areas, is placed in the coherer circuit, and is itself shunted by the
battery and the circuit of the receiving instrument, or by a Wheatstone bridge
system, whose resistances are in this case preferably anti-inductively wound.
Figure 4 shows the connexions for this arrangement of the condenser a, all the
letters of reference depicting the same parts as in the previous figures, and the
simple battery connexion of Figures 1 and 2 being shown. For the Wheatstone-
bridge plan the connections off aud 9 in Figure 4 are to be as shown in the ar-
rangement of Figure 3 but no other change need be made. This plan is almost as
affective as the previous one because steady currents from the battery must pass
through the coherer, ignoring the condenser, while alternations from the receiver
also act freely on the coherer, through the condenser, ignoring the receiving
instrument.
It is desirable to be able to arrange a coherer so that it shall receive unshunted
the whole of the impulse from a receiver or collector of any kind; and to that end
we employ in connection therewith a revolving switch or commutator designed to
successively connect the coherer:-(1) with the collector, or with the capacity
areas of a gyntonic receiver, so as to be cohered; (2) with the battery and tele-
graphic circuit so as to detect, display or record an effect due to this coherence;
(3) to break coherer connection and close a local circuit which shall cause a
incchanical tap or other suitable tremor so as to produce decoherence; or (as an
alternative to (3)) (4) instead of mechanical tapping-back, it is possible to
restore a coherer to sensitiveness in a very definite manner if it be arranged to
receive an impulse from an electric wave while it is connected to a closed circuit.
Hence instead of the process stated as No. (3) the commutator may be arranged so
as to momentarily connect the coherer with the receiver while the coherer is still
connected to the battery and telegraph circuit, or while connected to a special or
extra circuit without any receiving instrument in it; and in that case, if the
impulse is strong enough, it will be knocked back, not so completely as if tapped,
but sufficiently, and always into a position of considerable sensitiveness. (5) the
last operation which the revolving commutator has to perform is to restore the
connexions as in (1) and so permit the cycle to recur. The commutator may
revolve quite rapidly, being only limited by the quickness of response and recovery
of the signalling instrument. If the impulses coming from a distant station are
not sufficient to effect the decoherence by process (4) (for a coherer is by no means
as responsive when it is joined up to a closed circuit as it is when joined to an
open one), then it is easy to make the revolving commutator while in position (4)
also excite momentarily a local small weak emitter, which shall have the desired
restoring effect independently of the distant signals; but we prefer the mechanical
method of tapping-back hereinbefore referred to as No. 3.
Thus (to summarise), in position (1) of the revolving commutator the coherer is
ready to receive all arriving waves; in position (2) it enables them to be recorded;
en position (3) the coherer will become partially decohered or restored to its sensi-
tive state, and then position (1) will recur.
Figure 5 shows in skeleton this commutator in elevation and end view respec-
tively and Figure 7 illustrates diagrammatically the complete arrangement and
connections adapted to a syntonic station, & is a driving pulley through which
an electric or other motor can revolve the commutator at a suitable speed.
1, 2 and 3 are brass contact pieces, let into the cylinder of insulating material of
which the commutator is composed, for the purpose of connecting certain spring
brushes or contact-makers for definite fractions of a revolution. Of these brushes
and are connected to the capacity areas b and c. c and are connected
together and go to one terminal of the coherer e. ³ and are likewise connected
together and to the other terminal of the coherer. f and are connected to the
terminals of the battery f and telegraphic instrument 9 respectively, or to the
Wheatstone bridge when that is used. The remaining pair of brushes are
connected to the lapping back circuit which may consist for instance of a battery t

page_text: and a simple make and break or single stroke electric bell arrangement (which
mechanically shakes or jogs the coherer whenever the appropriate electric contact
is made. This in the arrangement shown is done twice at each revolution of the
commutator, because the brass pieces 3, 3 ure permanently joined to each other as
shown in a left hand section of Figure 5, and these bridge across the interval
1etween the brushes whenever they come round.
A coherer i sensitive not only to the desired impulse arriving from a distance
and collected by the appropriate receiver, but it is also liable to respond to any
local sparks or electric surgings in its neighbourhood, specially to oscillatious
in the adjacent sender; but it may be protected from all these by thorough short-
circuiting or by complete enclosure in a flawless metallic box.
For the purpose of protecting the coherer from undesired disturbance, therefore,
we enclose it as indicated in Figure 7, (sometimes together with all coils wires
batteries etc., connected to it) in a metallic covering or case, leaving only round
holes or short tubes for the collector terminals to enter by, and for vision or any
other needful purpose requiring an aperture. For through round holes of
moderate size large electric waves do not readily pass, whereas through chinks or
long slits, no matter how infinitely narrow, they can pass with ease. They like-
wise pass in by means of any insulated wire which enters the box, no matter how
short it may be, but through any wire which is thoroughly joined to the metal
wall of the box where it enters, the waves cannot pass. Hence it is not absolutely
necessary to remove the terminals from their apertures when they are not being
used for the purpose of establishing communications and enabling waves from the
receiver to enter the box and reach the coherer; for these same terminals m and n
may, when they are raised, completely plug with metallic continuity the small holes
through which they can freely afterwards be lowered. The holes may be protected
by a sheet of insulating material perforated to act as guides to the rods. The
only part of the coherer or detector portion that need be outside the box is the
index of the telegraph instrument employed (for convenience it is shown in quite
another part of the circuit in Figure 7) which can be acted upon, and deflected
by its coil inside acting magnetically through the metal wall. When the plan
of withdrawing the terminals of the box is adopted it is sufficient to put the
coherer alone in the box as shown in Figure 7. Anything protruding through an
aperture into the box, except the wire leading to the receiver when joined for
receiving," must either be there joined metallically up to the walls of the box,
or must be a non-conductor.
In order to use the same identical capacity areas and self inductance coil alter-
nately as emitter and as receiver, we have devised a switch which effects at one
motion the necessary connexions and alterations. Figure 6 shows the switch in
plan and elevation, and Figure 7 shows diagrammatically all the connexions of a
complete station on this plan. Referring first to Figure 6 the knob 7 of the
switch is to be depressed for sending and raised for receiving. m, n are the contact
pins which when lowered dip into mercury cups m³, n' or otherwise thereby making
contact between the coherer e and any desired apparatus connected to them, and
when raised have their conical ends forcibly plugged into the holes of the box
through which they pass to reach the coherer. o, o are simple spring contacts
for conveniently making or breaking the colerer circuit connexion with the
capacity areas. pand pure similar contacts for making or breaking the battery
and signalling key connexions with the sending Ruhmkorff coil u, and at the same
time (if necessary) of unclosing a latch y which otherwise short circuits the spark
gap between the capacity areas, which as shown in Figure 7 are supplied with their
opposite charges by the knobs r and s connected to the secondary terminals of the
Ruhukor (as previously described in the Specification of prior Letters
Patent No. 11576 dated May 10, 1897). is the battery for the tapper back '.
Bis the battery for the Ruhmkorff coil . The key for sending the message is a
simple arrangement as shown in Figure 7 for starting the Rulimkorff coil u into

page_text: its ordinary action and keeping it in action with a torrent of sparks at r and s as
long as the key w is depressed. is a sending relay and its battery.
The operations required are:-For preparing to receive signals, (1) close the
park gap between the capacity areas b and c, which can be done by the latch
which falls into its place except when raised by a relay or local magnet circuit
operated by the switch just mentioned; (Il bring down the pair of terminals m
and n into contact with the coherer-circuit inside its metal box ; and (III) com-
plete the connexion between the capacity areas and coherer circuit (through the
appropriate commutator brushes) by means of the contacts, o, o'. All this is done
at one operation by raising the end of the switch shown in Figures 6 and 7.
For preparing to transmit signals (I) raise the pair of terminals m and in out of
contact with the coherer-circuit, and either plug them tight into holes in the box-
wall or remove them completely from it; (II) break contact at the springs o, of
so as to detach the capacity areas electrically from the coherer circuit; (III) unclose
the spark gap between the capacity areas by means of the local magnet circuit
operated from the sending battery B and the contacts p, p; and (IV) close the
main gap in the circuit, likewise at p, p, which connects the Ruhmkorff coil u
with its battery B and with the sending relay which is worked by the signalling
key ; thus leaving to the latter the final closing and regulation or production of
intelligible signals, by means of sparks supplied at the knobs r, s to the capacity
areas b, c from the Ruhmkorff secondary. All this is done at one operation of the
switch, by depressing its knob Z.
One end of the switch whose function we have now described is depressed and
left down in its clamp so long as receiving is desired, the other end is depressed
and left down in its clamp so long as sending is desired, that is to say so long
as the separate transmitting key to, with its relay (which may be an automatic
transmitter) is being worked. The receiving end should be left down whenever
active transmission is not going on.
By the means now described the coherer may be completely isolated and will not
feel the waves sent out from its own station, while yet, when properly switched
on, it is perfectly sensitive to waves of proper frequency arriving from a distance.
We find that instead of keeping the coherer in a box it is often sufficient to very
thoroughly short-circuit it when not desired to receive; and this can be readily
done by a slight modification of the above described switch.
The signalling key can only be used when the switch is "down" for sending.
At other times, when the switch is "up" for receivjug, the signalling key is
iuoperative.
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 the radiating or absorbing portion of a system of syntonic Hertzian wave
telegraphy, the combination, with a pair of capacity areas and a self-inductanco
coil, of a condenser inserted in the current region between the two areas substan-
tially as and for the purpose set forth.
2. In a system of syntonic Hertzian wave telegraphy, a receiving circuit
arranged substantially as set forth with reference to Figure 4 of the acompanying
drawings.
3. In a system of Hertzian wave telegraphy, means whereby the coherer is
alternately connected (1) to a collector, (2) to a detector or recorder, and
(3) subjected to a decohering arrangement.
4. In a system of Hertzian wave telegraphy, means, substantially as set forth,
for protecting the colerer from the impulses from its own station, and for exposing
it to the impulses from a distant station, at pleasure.
5. In a system of Hertzian wave telegraphy, a switch adapted to change all tho
connexions over from "sending" to "receiving" at one operation constructed and
arranged substantially as set forth.

page_text: 6. The construction arrangement and combination of parts constituting our
system of syntonic Hertzian wave telography substantially as set forth with refer-
ice to Figure 7 of the accompanying drawings.
Dated this 7th day of September 1898.
A. F. SPOONER,
323, High Holborn, London, Agent for the Applicant.