Improvements in Electric Signalling.
Year: 1898

page_text: SILVANUS PHILLIPS THOMPSON, of Morland, Chislett Road, West Hampstead,
Doctor of Science, do hereby declare the nature of this invention to be as follows:-
My invention relates to electric signalling by periodic currents and periodic
magnetic fields and has for its object the improvement of the methods of receiving
and picking up such signals and of the instruments for effecting the same. For
receiving the signals I employ special forms of periodic galvanometer or electric
vibrator having a moving part mechanical, acoustical or optical the period of
which is itself adjusted or tuned to the frequency of the signal, or I employ an
adaptation of the said periodic instrument with contacts to act as a relay. This
instrument galvanometer vibrator or relay I insert either directly or inductively
in the receiving circuit which may be a simple wire circuit, or a line circuit with
earth return, or a cable circuit, or it may be a secondary circuit receiving signals
by induction, or it may be for wireless telegraphy a mere induction loop of appro-
priate form, or a suitable line earthed at both ends, or in some cases a tuned
circuit, that is to say one having both suitable self-induction and suitable capacity.
In some forms of my said instrument I employ an auxiliary periodic magnetic
field of equal or nearly equal period with that of the signals to act selectively and
with precision, or I make use of a rotatory field of equal period or some even sub-
multiple thereof, or I substitute a mechanical or electromagnetic vibrator of equal
period as an auxiliary in the receiving mechanism.
Dated this Seventh day of January 1898.
Improvements in Electric Signalling.
I, SILVANUS PHILLIPS THOMPSON, F.R.S., Doctor of Science, Morland, Chislett
Road, West Hampstead, London, 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 invention relates to electric signalling by periodic currents and periodic
magnetic fields and has for its object the improvement of the methods of receiving
and picking up such signals and of instruments for effecting the same.
It is known that periodic, that is to say, alternating or oscillating electric currents
can be produced in several ways: as by the use of revolving magnets or revolving
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page_text: coils as in alternate-current generators for electric light, or by the production of
a sudden disturbance such as an electric discharge or spark in an electric circuit
possessing both capacity and self-induction, or by means of induction coils with
vibrating breaks. It is also known that signals can be sent by the use of alternat-
ing or periodic electric currents. It is further known that alternating or periodic
electric currents flowing round a circuit set up alternating or periodic magnetic
fields transversely through the space surrounded by such circuits. It is known
that by such periodic magnetic fields spreading into adjacent space signals
can be transmitted from a primary circuit to a totally disconnected secondary
circuit laid down, for example upon the ground, at some distance from the place
where the primary circuit is laid out. It is known that if a circuit is tuned so
as to have a definite period of its own it will more readily respond to the inductive
effect of periodic magnetic fields if its own period of tuning be equal to that of
the impressed field. It is also known that the period of any circuit can be increased
by increasing its capacity, or its self-induction, or both. Finally it is known that
instruments such as relays can be constructed, and have been used by Elisha
Gray, Langdon Davies, Lodge and others, in which the moving part, consisting of
a tuned reed or a tuned stretched ribbon, is sensitive to impulses that arrive with
the corresponding frequency.
According to my improvements in electric signalling, the tuning is carried
right throughout the signalling system from beginning to end.
With this intent a periodic source of electric impulses, including any one of
those enumerated above, is employed, together with some suitable key or interrupter
for breaking up the vibrations into groups or into series of greater or less number
to represent dots or dashes, as a tuned transmitter. The said transmitter is caused
to impart its signals, whether directly or by spark-disturbances, to a tuned primary
circuit laid out upon the ground so as to enclose a considerable area.
This primary
circuit sets up a periodic magnetic field of equal frequency to that to which it is
itself tuned. At the distant spot where the signal is to be received there is laid out
a similarly tuned secondary circuit to receive the inductive action of the magnetic
field, and this circuit is in turn connected to a similarly tuned receiving instru-
ment.
Having now generally set forth the methods I turn to the instruments for effect-
ing the receiving and picking up of such signals. The receiver which I prefer
consists of a tuned mechanism of which there may be many varieties. In one form
a small bar-magnet or bar of iron is rigidly attached to a torsion wire near its
middle; is placed between the poles of a magnet; is surrounded longitudinally by
a coil or coils that are included in the receiving circuit. By tightening or slack-
ening the tension on the torsion wire, or by changing its length it is brought to
the requisite frequency. In another form an arm attached to a tuned torsion wire
or rod carries an iron armature placed close to the pole or poles of a telephonic
receiver. In a third form a suspended or pivotted coil which is included in the
receiving circuit is placed within a fixed coil through which auxiliary periodic
currents are passed of a frequency identical with that of the currents which are to
be used in signalling. In a fourth form the suspended or pivotted coil is placed
within a revolving magnetic field of equal frequency. In all cases the moving
part whether magnet, armature, or coil can be either fitted with a mirror (like a
galvanometer) for optical observation, or can be fitted with contact points to serve
as a relay, these being well known devices.
In the accompanying drawings:
Figure 1 represents the transmitting part of the apparatus. G is an alternate-
current generator say of 200 periods per second. Its currents are led through a
suitable manipulating key diagrammatically represented at H either directly to
the primary circuit, or preferably as shown, to a transformer T which transforms
these periodic currents to a higher voltage. In some cases a pair of polished metal
balls B B are added to constitute a spark gap so as to make the periodic disturbances

page_text: more abrupt. The transmitting primary circuit P consists of a wire or wires laid
out around a large area, and it must be tuned to the like frequency of 200 periods
per second by adding sufficient capacity and self-induction (either or both) as
represented diagrammatically at K K and L¹ L².
Figure 2 represents the distant receiving part of the system. The secondary
circuit S consisting of a wire or wires laid out around an area is in like manner
tuned by the insertion of capacity and self-induction as represented at K³, K' and
LL. In this secondary circuit is inserted the tuned receiving instrument, relay,
or galvanometer. The particular form indicated in Figure 2 consists of a coil C
surrounding a short magnet or piece of iron N S which is fixed upon a suitable
torsion wire or rod W, which must be tuned to the frequency of the system. The
suspended magnet is placed between the poles of a controlling magnet M. The
induced currents picked up by the tuned secondary circuit S tend to set the short
magnet N S into synchronous vibration. In the figures no attempt has been made
to show how the vibrating movements of the receiver (in this case the short mag-
net NS) can actuate a light mirror or operate the contacts of a relay as these are
matters perfectly known in the art.
Figure 3 shows how the primary and secondary parts of the system act inductively
upon one another.
EE represents a portion of the earth's surface, over which each
of the circuits P and S is laid. The periodic currents in P set up a periodic
magnetic field the lines of which M M are indicated. Some of these act inductively
through the circuit S, setting up periodic currents therein.
Figure 4 shows another form of receiving instrument in which an iron armature
A secured on arm A¹ is suspended by a tuned torsion wire or rod W secured be-
tween clamps W₁ the secondary circuit is connected to the coil C of an ordinary
telephone receiver the magnet of which is shown at N S. Any suitable description
of magneto-telephone receiver may be utilised in this manner. The secondary
currents passing round the coil act on the iron armature A and set it into
synchronous vibration.
Figure 5 represents another form of receiving instrument consisting of a coil C
which receives the currents from the secondary circuit, suspended within a larger
coil XX through which are passed auxiliary periodic currents of the same fre-
quency as those in the transmitting system. The coil C tends then to turn, and
by turning may operate a relay or galvanometer.
Figure 6 represents another form of receiving instrument. A coil Cincluded
in the secondary circuit is suspended within a revolving magnetic field. This is
diagrammatically represented by a gramme ring overwound with wire to form a
closed circuit. At three equidistant points on the winding are connected three
wires 1, 2, 3 which bring an auxiliary three-phase current of the same frequency
as the system. These generate a rotatory magnetic field within the ring. The
coil C, if it receives from the secondary, periodic currents of equal frequency, will
tend to turn and so operate a relay or move a galvanometer mirror.
Figure 7 illustrates a device which is convenient to employ at the transmitting
end when the last-named form of receiving instrument is used. The alternator G
is one which generates currents in two different phases in two different circuits,
as well-known in the art. The ends of these circuits are so grouped that a two-way
key K may throw them alternating into the primary circuit, or into the trans-
former T which leads to the primary. By thus varying the phase of the transmitted
impulses the coil C in the receiving instrument may be acted upon so as to produce
deflexions in one sense or the other according to which of the two circuits of the
alternator is employed.
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 system for electric signalling by periodic electric currents, the com-

page_text: bination of a tuned receiver, relay or instrument with similarly tuned secondary
and primary circuits, and means for transmitting into the primary circuit periodic
impulses of similar period grouped as signals.
2. In a system for electric signalling by periodic electric currents, a receiving
instrument consisting of a moveable part of a circuit combined with an auxiliary
circuit into which are introduced alternating currents of equal frequency with
those employed in the transmitted signals.
3. An electric signal receiving apparatus consisting of a coil which can move or
vibrate combined with a rotatory magnetic field produced by auxiliary alternating
currents of equal frequency with those employed in the transmitted signals.
4. In the transmission of electric signals by periodic currents, the employment
alternately of two periodic currents of equal frequency but differing in phase,
substantially as described.
1000
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C. Patent Agents for the Applicant.