Improvements relating to Telephone, and to Circuit Arrangements and Relays therefor.
Year: 1898

page_text: Date of Application, 27th Apr., 1898
Complete Specification Left. 13th Dec., 1898-Accepted, 13th Jan.,
1899
PROVISIONAL SPECIFICATION.
Improvements relating to Telephone, and to Circuit Arrangements
and Relays therefor.
I. OLIVER JOSEPH LODGE, F.R.S.. D.Sc.. of 2. Grove Park, Liverpool. in the
County of Lancaster. Professor of Physics in University College, Liverpool, afore-
said. do hereby declare the nature of this invention to be as follows:-
The chief objects of my invention are to provide means for the audible detection
of extremely feeble fluctuating electric currents such, for instance, as may be
caused in a closed, or practically closed. circuit by another very distant circuit
supplied by alternating currents: to magnify the telephonic effect of feeble currents
by successive specially designed relays until the sound is sufficient to act as a "call "
Summoning the operator to attend to receive the message: to magnify the tele-
phonic effect of speech so that conversation transmitted round one circuit may be
heard inductively in a different circuit provided with proper instruments: and
generally to improve the conditions under which telephony is carried on so as to
magnify enormously every fluctuation of current and thus produce a loud sound
from a feeble stimulus for any useful purpose.
For the purpose of detecting or manifesting any feeble alternating or inter-
mittent current. whether excited microphonically or inductively or otherwise. I
construct a special kind of telephone or relay consisting of a fine wire coil sub-
ported elastically in a strong maometic field in such a war that it is thrown into
ribration as a whole when an alternating or intermittent current is sent round
it. This coil may be attached to a metal diaphragm held near the ear, or to a sound
board upon which the ear is laid, but I usually in the first instance attach it
mechanically to the diaphragm of granular microphone or to some other micro-
phonic arrangement fed by a local battery and having in its circuit (through a
transformer or otherwise) another telephone, which may be either of any usual
pattern or of the above described new pattern with vibrating coil. This second
movable or trembling coil may thus actuate by mechanical means another micro-
phone which, through the energy of its relay battery, may powerfully disturb a
third telephone, and this again if necessary a fourth and so on.
By this means any required degree of magnification can he attained. For I
find that a coil thus moving as a whole in a magnetic field (otherwise maintained)
is very suitable for communicating its tremors to a microphone-transmitter
whether of special or of any customary form: being much more effective for
this purpose than the ordinary iron diaphragm receiver which vibrates in narts
and is under considerable constraint. The final telephone of the series is usually a
loud sneaking iron disc or diaphragm telephone of some ordinary pattern svitable
or it may be an electro-
for imparting vibrations to the air and so to the ear:
dynamometric syphon-recorder, or a Langdon-Davies phonophoric receiver, or other
instrument whereby the vibrations are enabled to work Morse or other telegraph
instruments.
) I may use this plan of magnification as a call. or as a receiver in magnetic

page_text: at
therefor
telegraphy, but it is obviously applicable to other useful purposes. I call it
bellowing telephone because a gentle tone at one end of the series becomes a vit
Further I find that a microphone acts best when a certain strength of current
is passing through it; so whenever the receiving telephone is of too high resistans
to permit this strength of current to How in simple circuit with it I shunt the
telephone by means of a low resistance self-induction or choking coil, which co
ducts the main part of the steady current but diverts the variations of current
through the telephone. On a long line a transformer is the natural mode of
achieving this object but on a short or purely local line I find the choke hant
preferable.
Also I may interpose a condenser in series with the telephone so as in combina
tion with the above self-induction coil, or in any case in combination with the
rest of the circuit. to strengthen oscillations of some particular frequency in especiai,
and of all frequencies not too far removed from that.
I usually connect the vibrating coil of the receiving telephone relay direct in
the microphone of the next circuit by light solid rod connections, or by threads
by cement, but I may arrange to do it also acoustically through the air, or through
a liquid in which the microphonic contacts are immersed, or in any other effective
fashion.
The field magnet of the telephone relay is a special ironclad arrangement suit.
able for giving an annular field of great intensity in which the moving coil is
suspended or otherwise supported with sufficient freedom to experience tremor
but with sufficient elastic constraint to balance its inertia at a certain frequener
of vibration. The movable coil is not intended to magnetise any iron and is mainly
surrounded by fixed conducting masses in which Foucault or eddy currents are
freely permitted so as to keep down the impedance of the coil. The field magnet
is usually excited by a local battery, but it may be a permanent magnet in cases
when that is strong enough.
Whenever a temporarily inoperative microphone is in circuit with a
(as for instance the ordinary transmitter belonging to a local receiver during the
telephone s
reception of a distant message) and where its elimination by a transformer is not
convenient I shunt out it and its battery by means of a condenser. Also I may use
a choke coil as a shunt of the received current in such a war that for notes of
certain pitch the telephone shall respond freely to the desired disturbance. but to
disturbance from its own microphone it shall be comparatively deaf.
This and the other methods mentioned, though specially applicable to such pure
tone telephony as is appropriate for Morse signals, can also be used with speech
telephony under certain conditions.
As microphonic transmitter to be disturbed by the moving coil I may arrange
carbons supported directly on the coil, with microphone bridges in parallel across
them, using fibres or spheres or spindles or any other shaped bridges, and with
other special methods for securing suitable kinds of contact.
Further I may arrange a number of annular air gaps in the same field magnet.
each provided with its moving coil and microphone: and these connected up each
to its own battery may be the series of magnifying telephones hereinbefore referred
to.
Moreover I may immerse the carbons or other microphonic materials in water.
or oil, or other liquid, and communicate the tremor of the coil to the liquid in any
mechanical way; either by direct immersion of the end of a rod or a plate or by a
flexible diaphragm, such as the bottom of the vessel which holds both liquid and
compound microphone. The specific gravity of the liquid may be adjusted to
secure the most suitable light pressure.
Instead of carbon I may use metallic or other contacts, and they may be
immersed in a liquid or in a vacuum. Or I may use two surfaces not quite in con-
tact in a well-conducting vacuum, and with a difference of temperature or of
electric potential maintained between them.

page_text: so I may use differentially-wound or other transformers for the purpose of
communicating electrically between each microphone and the receiving or vibrat-
iur
oil of the next in the series. The vibrating coils may be wound of fine wire
compacted together with cement has shellar, or they may be of metallic ribbon
when extra low resistance is desite.
turk or
Furthermore for the purpose of a "cail."-telephone such as a tuning
other persistent vibrator mounted on a sound board may be employed as the
last of the series of telephone relays, so as to respond powerfully when alternating
curients of its own frequency are excited at the distant station.
For the purpose of discriminating between a number of call stations a combina-
tion of differently attuned forks or tone-telephones may be arranged instead of
que, so that each shall respond strongly only to its own note and thus indicate the
particular station which is desiring to signal. The receiving or collecting circuit
may likewise in some cases be attuned to definite note At the sending end a
battery connected to an acoustic arrangement, such as a reed, or a string or other
rapid intermitter or reverser of current. may be used to stimulate a circuit contain-
ing both capacity and self induction, so that it shall be thrown into strong electro-
magnetic vibration.
A. E. SPOONER.
828, High Holborn, London, Agent for the Applicant.
Improvements relating to Telephones, and to Circuit Arrangements
and Relays therefor.
I. OLIVER JOSEPH LODGE. F.R.S.. D.Sc.. of 2. Grove Park. Liverpool. in the
County of Lancaster. Professor of Physics in University College. Liverpool. afore-
said, 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:-
"
The chief objects of my invention are to provide means for the audible detection
of extremely feeble fluctuating electric currents. s for instance as may be caused
in a closed, or practically closed, circuit, by a her very fit circuit supplied
with alternating currents: to maguity the telepenie turrents by
call"
successive specially-designed relays until the son is same ent an art as a
summoning the operator to attend to receive the message; a magnify the telephonic
effect of speech so that conversation transmitted and it may be heard
inductively in a different circuit provided with per instruments: and generally
to improve the conditions under which telephony is in so as to magnity
every Huctuation of current and thus produce a lui sa sem a teeble stimulus
for any useful purpose.
For the purpose of detecting or manifesting any weble iternating or inter-
mittent current. whether excited microphonically or inductively or otherwise. I
construct a special kind of telephone or relay, the main features of which are
depicted in the annexed drawings. It consists of a coil of insulated wire or metal
ribbon a supported freely by an elastic spring (Figure 35 or by one prong of a
tuning fork (Figure 1 in a strong magnetic field produced by an electromagnet
or permanent magnet e on which one pole is inside the coil while the other pole
or keeper is outside and surrounding it. The coil is constructed of light
materials well cemented or fixed together so as to move as a rigid body. and when-
ever an alternating current passes round it, it is thrown into bodily vibration, and

page_text: Therefor.
coil may be attached in any light and rigid manner to a sound board d (Figure 1,
viorations mechanically to whatever is connected to it. The said
a piece of graphite, carbon, or other suitable substance (Figures 2 and 3
that the sound board, the diaphragm, or the carbon, receive the mechanics
The object of transmitting the vibrations to the sound board d is to make them
directly audible. The object of transmitting them to the microphonic carbo
granules or pellet is to actuate a kind of microphonic relay which by throwing in
intermittent action the current from a local battery shall greatly magnify the 1
vibrations.
intensity of the originally received disturbance.
The sound-board receiver is depicted in Figure 1, where e is a thin aluminium
or other light cone or tripod connecting the vibrating roil a rigidly to the on
to it in various parts. For instance it might form the ceiling or wall of a publie
board d, which may be of large size and may have a number of similar coils attached
that case be caused by the voice of a speaker directed towards any form of micro-
hall; and the alternating current originally received by the several coils would is
phonic transmitter capable of distinct articulation.
In the case of Figure 1 the sound board d, or in the case of Figure; the
diaphragm A, itself constitutes the elastic support of the coil a and dispenses with
the necessity of the separate spring such as that showu at 6 in Figure 3. One
one end of the keeper is shown in Figures 1 and 2: the side of it is indicated
in Figure 3, and it continues to the other pole of the magnet which it similarly
surrounds as shown in Figures 5 and 5º. In all these figures, the keeper is sup
ported rigidly from the pole by means of a brass collar and plate f.
A form of magnet is shown in Figure + (which represents a plan and elevation
respectively) where the keeper c is a round plate of soft iron pierced with holes
for the reception of four poles like c and where co is a bundle of hard steel magneta
joined to the four rods c by an irou base plate 3.
arrangement, the whole is of soft iron and the space surrounding the central
Or else, as an alternative
shaft is fined with wire, constituting it an electromagnet.
four pole pieces like c' and four annular air gaps or inter pole spaces a³ to receive
Thus a magnet with
four vibrating coils such as u shown in the other figures is produced.
Figures 5 and 5 illustrate in plan: Figure 3 in side elevation: and Figure
in vertical section, an alternative form of steel magnet and its keeper. The magnets
is one of ordinary horseshoe shape with two poles and soft iron pole pieces d
surrounded by a soft iron keeper el attached rigidly by the brass collar-plate f
to the pole pieces.
The coil a instead of being attached to a metal diaphragm held near the ear.
or to a sound board as described, may in the first instance be mechanically attached
to the diaphragm of a granular microphone as shown in Figure 7 or to some other
microphonic arrangement fed by a local battery and having in its circuit (through
a transformer or otherwise) another telephone as shown in Figure 6, which may be
either of any usual pattern or of the above described new pattern with vibrating
coil. This second movable or trembling coil may thus actuate by mechanical
means another microphone which, through the energy of its relay battery, mar
powerfully disturb a third telephone, and this again if necessary a fourth and so
on. The whole arrangement is depicted in Figure : where the concluding tele
phone of the series is indicated in two alternative forms either of which may be
switched on by the switch m.
can be obtained. for I find that a coil thus moving as a whole in a magnetic field
By this means any required degree of magnification S
(otherwise maintained) is very suitable for communicating its tremors to a micro-
phone-transmitter whether of special or of any customary form: being much more
effective for this purpose than the ordinary iron diaphragm receiver which vibrates
in parts and is under considerable constraint. The final instrument of the series 5
s usually a loud speaking iron disc or diaphragm telephone of some ordinary
pattern suitable for imparting vibrations to the air and so on to the ear; or it may.

page_text: THT
be an
electro-dynamometer or a Langdon-Davies phonophoric receiver, or other
ustrument, for example, that shown in Figure S, whereby the vibrations are
enabled through a relay to work Morse or other telegraph instruments.
I may use this plan of magnification as a call, or as a receiver in magnetic
telegraphy, but it is obviously applicable to other useful purposes such as magnify-
ing a speaker's voice by distributing it to various parts of a large hall.
The main features of the microphonic relay or magnifying telephone are shewn
in detail in Figures 2 and 3, where the vibrating carbon is in light contact (it
shown separated in the figures for clearness) with another piece of carbon or
other electric conductor which is firmly held and adjusted by a thumb screw i
working in a suitable support j. It is to be understood that the support and the
or the prong of the tuning tork are to be connected to a local battery
ping
circuit which shall also be connected either directly or through a traustormer with
the coil of another second receiving telephone. This second telephone thus sup-
pied with intermittent or alternating currents of magnified intensity may be a
telephone of ordinary pattern, or it may be a vibratory coil telephone like Figure 1.
ur it may be another relay telephone like Figures 2 and 3 or like Figure which
then in turn magnifies further and operates another telephone, and so on.
Figure 6 serves to show the connexions for such a series of magnifying tele-
phones, or telephone relays. In that figure the coil and condenser indicated at A B
represents subject matter described in the Specification of another Application for
Letters Patent filed by me and numbered 29.505 dated 13 December 1897, though
it may be replaced by any other transmitting or collecting apparatus: for instance
this original current Huctuator might be an ordinary microphonic transmitter
operated by the voice. The Roman numerals I. II, III and IV represent a possible
arrangement of the receiving and magnifying apparatus. No. I is a relay telephone
like Figure 2 or Figure 3 with a vibratory coil varying the microphonic contact
of the carbons and h. one of them being supported by the spring b. No. II is
another relay telephone like Figure 7 adapted to stronger currents, with its
vibratory coil varying the microphonic contacts in a granular transmitter with its
thin carbon diaphragm and carbon base . No. III is a loud-speaking tele-
phone consisting of a vibratory coil and sound board. like Figure
represents another form of loud-speaking telephone, alternative to the last, where a
vibratory diaphragm disturbs the outer air through a concentrating tunnel. The
magnet in Nos. I II and III is supposed to be an electromagnet shaped like
Figure 4. but with ouly a single air gap surrounding the central shaft (, which
is wound with a magnetizing helix and surrounded by an outer iron cylinder
instead of the four rods c of that figure. The magnet of No. IV is supposed to
be more like the horseshoe pattern of Figures to 5 or it may be any known
form of loud-speaking telephone. Electrical connection between I and II and
between II and III is effected by means of the transformers k₁ and kand
are the local batteries, of which is permissibly stronger than . because of the
many contacts in the granular microphone. Instead however of the speaking
cail telephone may be employed. The
telephone No. III a modification calleil a
5 design of this is depicted in Figure 8 where the coil. suspended as before in a held
due to the magnet e by the rigid light connector e, operates the limb of a spring
or of a tuning fork 6 clamped to the pillar and carrying an adjustable counter-
poise for the purpose of equalizing the load on both prongs, and also permitting
The studs and
L' qare platinum. lightly in contact, the
a slight range of tuning.
0 upper one being held by the tuin spring - and adjusted by the thumb screw i
The pillar supporting this spring is insulated. as for instance by the ebonite
and thus and can be connected to a local battery circuit containing an ordinary
relay the tongue of which is just held over by the current across the junction p
so long as that junction is undisturbed. But directly the fork trembles. the
55 contact between p and q is practically broken or greatly enfeebled, by the dancing
of the light spring r on the heavier spring 64, and accordingly the tougue of the
No. IV

page_text: relay in circuit with (that is with . j) moves over and completes the circuit
of an ordinary electric bell or it may work a Morse instrument.
For the purpose of discriminating between a number of "call" stations a com-
bination of differently attuned forks or tone telephones may be arranged, instead
of one, so that each shall respond Strongly only to its own note and thus indic
or collecting
the particular station which is desiring to signal. The receiving
circuit may likewise be attuned to a definite note, as detailed in the specification
of my said prior application.
Whether the spring 6 or the tuning fork b₁ is employed as the elastic support
for the coil in any case is optional. but whenever precision of tuning is desir
so that the receiver shall respond to one particular frequency of distant impuis
and not to others. I prefer the tuning fork: and in that case it would be preferable
to make Nos. I. II and III of Figure 6 all tuning-fork telephones. But where
many notes, or where speech is desired to be received and magnified, then either
a spring or a diaphragm or some other elastic support can be used. Further I find t
that a microphone acts best when a certain strength of current is passing through
it so whenever the receiving telephone is of too high resistance to permit this
strength of current to How in simple circuit with it I shunt the telephone by means
of a low resistance self-induction or choking coil which conducts the main part
of the steady current but diverts the variations of current through the telephone.
On a long line a transformer is the natural mode of achieving this object but on
a short or purely local line I find the choke shunt preferable.
To enable a fairly strong current to be sent through a microphonic transmitter
without over-disturbing a telephonic receiver, I shunt the latter out by a self-
induction or choke coil t. as indicated in Figure 9, where the transmitter A¹ is
shown operated by one of the vibrating coils a as in Figure but its telephonic
receiver is shunted by the coil t, whereby the steady current is mostly conveyed,
while its rapid Huctuations mostly go through the telephone. To assist the
Huctuation to go through the telephone. I place a condenser u in series with it as
shown in Figure 10. This has the effect of strengthening oscillations of some
particular frequency in especial, and of all frequencies not too far removed from that.
It is to be understood that the microphone transmitter may be worked by the
voice or by any other usual arrangement, and is not limited to the disturbance
by attached coils.
Whenever a temporarily inoperative microphone is in circuit with a telephone
(as for instance the ordinary transmitter belonging to a local receiver during the
reception of a distant message), an accidental noise, a grating or hissing, is usually
going on in the telephone. This can be diminished by shunting the telephone with
a condenser v, as indicated in Figure 11. an arrangement which is advantageons
in some forms of ordinary voice telephones, as it diminishes the disturbing nois
trom the local transmitter while the desired message from a distant transmitte
is being listened to.
This and the other methods mentioned, though specially applicable to suc
pure-tone-telephony as is appropriate for Morse siguals, can also be used with
speech-telephony under certain conditions.
Having now particularly described and ascertained the nature of my sai
invention and in what manner the same is to be performed, I declare that wh
I claim is:-
1. A telephone having a coil freely supported in a magnetic field upon an elasti
spring or its equivalent substantially as and for the purposes set forth.
2. In a telephone, the combination of a coil freely supported upon an elast
spring or its equivalent with a magnet one pole of which is inside the coil whi
the other pole is outside and surrounding it substantially as and for the purpos
⚫ set forth.
3. The method, substantially as set forth, of attaining forcible mechanical
acoustic vibrations from fluctuating electric currents by a telephone consistir

page_text: of an
elastically suspended movable coil, suspended in an annular or other suit-
able magnetic field, and connected with a sound board, or its equivalent.
The method, substantially as set forth, of magnifying feeble mechanical
operate a
sibrations electrically received by means of a vibrating coil so arranged as to
microphone or microphonic transmitter whose current serves to work
another telephone.
3. The combination of a series of telephones and microphones connected alter-
nately electrically and mechanically. so that each telephone receives a disturbance
electrically from the preceding microphone and passes it on mechanically in
magnified intensity to the next microphone, while each microphone receives a dis-
turbance mechanically from the preceding telephone (or in the case of the first of
the series possibly from the voice direct) and passes it on electrically to the next
telephone of the series.
The microphonic relay or magnifying telephone constructed substantially as
described with reference to Figures 2 and 3 of the accompanying drawings.
A magnet with one or more inter pole spaces each containing' a suspende
coil of wire arranged to receive Huctuating currents and thereby to be thrown into
Vibration substantially as described with reference to Figure 4. or to Figures 5,
3.5%, and 5 of the accompanying drawings.
As a telephonic call," a light metallic contact in a local relay circuit
anged so that it dances on an elastic vibrator and thereby changes in electrical
resistance when the vibrator is excited by means of fluctuating currents sent round
an attached coil suspended in a magnetic field substantially as described with
reference to Figure of the accompanying drawings.
9. In a telephonic arrangement, the combination of a magnet, a mechanically
vibrating coil surrounding one of its poles, a microphone, and a telephone or its
equivalent substantially as and for the purposes set forth.
10. In combination, a tuning-fork or reed and a vibrating coil substantially as
and for the purposes set forth.
11. In combination, a tuning fork or reed. a vibrating coil and a loose contact
attached to the tuning fork for the purpose of operating a relay and so furnishing
a "call substantially as set forth.
12. In a telephonic circuit the choke coil & substantially as and for the purpose
set forth.
13. In a telephonic circuit the condenser & substantially as and for the purpose
set forth.
14. The combination. in a telephonic circuit. of the choke coil and the con-
denser substantially as and for the purpose set forth.
Dated this 13th day of December 1898.
A. F. SPOONER.
323, High Holborn. London. Agent for the Applicant.

page_text: Date of Application, 27th Apr.,
1000
1050
Complete Specification Left, 13th Dec., 1898-Accepted, 13th Jan.,
1899
Date of Application, ar Apr. 100
Complete Specification Left, 13th Dec., 1898-Accepted, 13th Jan.,
1899
PROVISIONAL SPECIFICATION.
Improvements relating to Telephones, and to Circuit Arrangements
and Relays therefor.
1
I, OLIVER JOSEPHI LODGE, F.R.S., D.Sc., of 2, Grove Park, Liverpool, in the
County of Lancaster, Professor of Physics in University College, Liverpool, afore-
said, do hereby declare the nature of this invention to be as follows:-
The chief objects of my invention are to provide means for the audible detection
of extremely feeble fluctuating electric currents such, for instance, as may be
caused in a closed, or practically closed, circuit by another very distant circuit
supplied by alternating currents; to magnify the telephonic effect of feeble currents
by successive specially designed relavs until the sound is sufficient to act as a "call"
summoning the operator to attend to receive the message; to magnify the tele-
phonic effect of speech so that conversation transmitted round one circuit may be
heard inductively in a different circuit provided with proper instruments; and
generally to improve the conditions under which telephony is carried on so as to
magnify enormously every fluctuation of current and thus produce a loud sound
from a feeble stimulus for any useful purpose.
For the purpose of detecting or manifesting any feeble alternating or inter-
mittent current. whether excited microphonically or inductively or otherwise, I
construct a special kind of telephone or relay consisting of a fine wire coil sup-
ported elastically in a strong magnetic field in such a way that it is thrown into
vibration as a whole when an alternating or intermittent current is sent round
it. This coil may be attached to a metal diaphragm held near the ear, or to a sound
board upon which the ear is. laid, but I usually in the first instance attach it
mechanically to the diaphragm of a granular microphone or to some other micro-
phonic arrangement fed by a local battery and having in its circuit (through a
transformer or otherwise) another telephone, which may be either of any usual
pattern or of the above described new pattern with vibrating coil. This second
movable or trembling coil may thus actuate by mechanical means another micro-
phone which, through the energy of its relay battery, may powerfully disturb a
third telephone, and this again if necessary a fourth and so on.
By this means any required degree of magnification can be attained. For I
find that a coil thus moving as a whole in a magnetic field (otherwise maintained)
is very suitable for communicating its tremors to a microphone-transmitter
whether of special or of any customary form; being much more effective for
this purpose than the ordinary iron diaphragm receiver which vibrates in parts
and is under considerable constraint. The final telephone of the series is usually a
loud speaking iron disc or diaphragm telephone of some ordinary pattern suitable
or it may be an electro-
for imparting vibrations to the air and so to the ear:
dynamometric syphon-recorder, or a Langdon-Davies phonophoric receiver, or other
instrument whereby the vibrations are enabled to work Morse or other telegraph
instruments.
I may use this plan of magnification as a call, or as a receiver in magnetic

page_text: telegraphy, but it is obviously applicable to other useful purposes. I call it a
bellowing telephone because a gentle tone at one end of the series becomes a shout
at the other end.
Further I find that a microphone, acts; best,, when a certain strength of current
is passing through it; so whenever the receiving telephone is of too high resistance
to permit this strength of current..to flow in simple circuit with it I shunt the
telephone by means of a low resistance self-induction or choking coil, which con-
ducts the main part of the steady current but diverts the variations of current
through the telephone. On a long line a transformer, is the natural mode of
achieving this object but on a short or purely local line I find the choke shunt
preferable.
Also I may interpose a condenser in series with the telephone so as in combina-
tion with the above self-induction, coil,, or in any case in combination with the
rest of the circuit, to strengthen oscillations of some particular frequency in especial,
and of all frequencies not too far removed from that.
I usually connect the vibrating coil of the receiving telephone relay direct to
the microphone of the next circuit by light solid rod connections, or by threads or
by cement, but I may arrange to do it also acoustically through the air, or through
a liquid in which the microphonic contacts are immersed, or in any other effective
fashion.
The field magnet of the telephone relay is a special ironclad arrangement suit-
able for giving an annular field of great intensity, in which the moving coil is
suspended or otherwise supported with sufficient freedom to experience tremor
but with sufficient elastic constraint. to balance its inertia, at a certain. frequency
of vibration. The movable coil is not intended to magnetise any iron. and is mainly
surrounded by fixed conducting masses in which Foucault or eddy currents are
freely permitted so as to keep down the impedance of the coil. The field magnet
is usually excited by a local battery, but it may be a permanent magnet in cases
when that is strong enough.
Whenever a temporarily inoperative microphone is in circuit with a telephone
(as for instance the ordinary transmitter belonging to a local receiver during the
reception of a distant message) and where its elimination by a transformer is not
convenient I shunt out it and its battery by means of a condenser. Also I may use
a choke.coil as a shunt of the received current, in. such a way that for notes of
certain pitch the telephone, shall respond freely to the desired disturbance, but, to
disturbance from its own microphone it shall be comparatively deaf.
This and the other methods mentioned, though specially applicable to such pure
tone telephony as is appropriate for Morse signals, can also be used with speech
telephony under certain conditions.
As microphonic transmitter to be disturbed by the moving coil I may arrange
carbons, supported directly on the coil, with. microphone bridges in parallel, across
them, using fibres or spheres or spindles or any other shaped bridges, and with
other special, methods for securing suitable kinds of contact.
Further I may arrange a number of annular,air gaps. in the same, field magnet,
each provided with its moving, coil and microphone; and these connected up each
to its own battery may be the series of magnifying telephones herein before referred
.to.
Moreover I may immerse the carbons .or, other microphonic materials in water.
or oil, or other, liquid, and communicate the tremor of the coil to the liquid in any
mechanical way; either by direct immersion of the end of a rod or a plate or by a
flexible diaphragm, such as the bottom of, the vessel which holds both liquid and
compound microphone. The specific gravity of the liquid may be adjusted to
secure the most suitable light pressure.
Instead of carbon I may use metallic or other contacts, and they may be
immersed in a liquid or in a vacuum. Or I may use two surfaces not quite in con-
tact in a well-conducting vacuum, and with a difference, of, temperature or of
electric potential maintained between them,

page_text: Also I may use differentially-wound or other transformers for the purpose o
communicating electrically between each microphone and the receiving or vibrat-
ing coil of the next in the series. The vibrating coils may be wound of fine wire
compacted together with cement such as shellac, or they may be of metallic ribbon
when extra low resistance is desired.
Furthermore for the purpose of a call," a tone-telephone such as a tuning
fork or other persistent vibrator mounted on a sound board may be employed as the
last of the series of telephone relays, so as to respond powerfully when alternating
currents of its own frequency are excited at the distant station.
For the purpose of discriminating between a number of call stations a combina-
tion of differently attuned forks or tone-telephones may be arranged instead of
one, so that each shall respond strongly only to its own note and thus indicate the
particular station which is desiring to signal. The receiving or collecting circuit
At the sending end a..
may likewise in some cases be attuned to a definite note.
battery connected to an acoustic arrangement, such as a reed, or a string or other
rapid intermitter or reverser of current, may be used to stimulate a circuit contain-
ing both capacity and self induction, so that it shall be thrown into strong electro-
magnetic vibration.
1000
A. F. SPOONER,
323, High Holborn, London, Agent for the Applicant.
Improvements relating to Telephones, and to Circuit Arrangements
and Relays therefor.
I, OLIVER JOSEPH LODGE, F.R.S., D.Sc., of 2, Grove Park, Liverpool, in the
County of Lancaster, Professor of Physics in University College, Liverpool, afore-
said, 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:-
"
"
call
The chief objects of my invention are to provide means for the audible detection
of extremely feeble fluctuating electric currents, such for instance as may be caused
in a closed, or practically closed, circuit, by another very distant circuit supplied
with alternating currents; to magnify the telephonic effect of feeble currents by
successive specially-designed relays until the sound is sufficient to act as a
summoning the operator to attend to receive the message; to magnify the telephonic
effect of speech so that conversation transmitted round one circuit may be heard
inductively in a different circuit provided with proper instruments; and generally
to improve the conditions under which telephony is carried on so as to magnify
every fluctuation of current and thus produce a loud sound from a feeble stimulus
for any useful purpose.
For the purpose of detecting or manifesting any feeble alternating or inter-
mittent current, whether excited microphonically or inductively or otherwise, I
construct a special kind of telephone or relay, the main features of which are
depicted in the annexed drawings. It consists of a coil of insulated wire or metal
ribbon a supported freely by an elastic spring b (Figure 3) or by one prong of a
tuning fork (Figure 2) in a strong magnetic field produced by an electromagnet
or permanent magnet e of which one pole c is inside the coil while the other pole
or keeper c is outside and surrounding it. The coil is constructed of light
materials well cemented or fixed together so as to move as a rigid body, and when-
0 ever an alternating current passes round it, it is thrown into bodily vibration, and

page_text: transmits these vibrations mechanically to whatever is connected to it. The said
coil may be attached in. any light and rigid manner to. a sound boarded (Figure 1)
or, to the diaphragm (Figure 7) of a microphonic transmitter, or it may carry-
a. piece of graphite, carbon, or other suitable substance (Figures 2 and 3), so
that the sound board, the diaphragm, or the carbon, receive the mechanical
vibrations.
The object of transmitting. the vibrations to the soundboard d. is to make them
directly audible. The object of transmitting them to the microphonic carbon
granules or pellet is to, actuate a kind of microphonic relay which. by throwing into
intermittent action the current from a local battery shall greatly, magnify, the
intensity of the originally received disturbance.
The sound-board. receiver is depicted in Figure 1, where e is a thin aluminium
or other light cone or tripod connecting the vibrating roil a rigidly to the sound
board d, which may be of large size and may have a number of similar coils attached
to it in various parts. For instance it might form the ceiling or wall of a public
hall; and the alternating current originally received by the several coils would in
that case be caused by the voice of a speaker directed towards any form of micro-
phonic transmitter capable of distinct articulation.
In the case of Figure 1 the sound board d, or in the case of Figure 7 the
diaphragm, itself constitutes the elastic support of the coil and dispenses with
the necessity of the separate spring such as that shown at 6 in Figure 3. Only
one end of the keeper c¹¹ is shown in Figures 1 and 2; the side of it is indicated
in Figure 3, and it continues to the other pole of the magnet which it similarly
surrounds as shown in Figures 5* and 5°. In all these figures, the keeper is sup-
ported rigidly from the pole by means of a brass collar and plate f.
A form of magnet is shown in Figure 4 (which represents a plan and elevation
respectively) where the keeper c is a round plate of soft iron pierced with holes
for the reception of four poles like c¹ and where co is a bundle of hard steel magnets,
joined to the four rods c¹ by an iron base plate c. Or else, as an alternative
arrangement, the whole is of soft iron and the space g surrounding the central
shaft is filled with wire, constituting it an electromagnet. Thus a magnet with
four pole pieces like c¹ and four annular air gaps or inter pole spaces a* to receive
four vibrating coils such as a shown in the other figures. is produced.,
Figures 5 and 5* illustrate in plan; Figure 5" in side elevation; and Figure 5°
in vertical section, an alternative form of steel magnet and its keeper. The magnet
is one of ordinary horseshoe shape with two poles c and soft iron pole pieces c¹
surrounded by a soft iron keeper c" attached rigidly by the brass. collar-plate f
to the pole pieces.
The coil a instead of being attached to a metal diaphragm held near the ear,
or to a sound board as described, may in the first instance be mechanically attached
to the diaphragm of a granular microphone as shown in Figure 7 or to some other
microphonic arrangement fed by a local battery and having in its circuit (through
a transformer or otherwise) another telephone as shown in Figure 6, which may be
either of any usual pattern or of the above described new pattern with vibrating
coil. This second movable or trembling coil may thus actuate by mechanical
means another microphone which, through the energy of its relay battery, may
powerfully disturb a third telephone, and this again if necessary a fourth and so
on.
The whole arrangement is depicted in Figure 6; where the concluding tele-
phone of the series is indicated in two alternative forms either of which may be
switched on by the switch m. By this means any required degree of magnification
can be obtained, for I find that a coil thus moving as a whole in a magnetic field
(otherwise maintained) is very suitable for communicating its tremors to a micro-
phone-transmitter whether of special or of any customary form; being much more
effective for this purpose than the ordinary iron diaphragm receiver which vibrates
in. parts and is under considerable constraint. The final instrument of the series
is usually, a loud speaking iron disc or diaphragm telephone of some ordinary
pattern suitable for imparting vibrations to the air and so on to the ear; or it may

page_text: be an electro-dynamometer or a Langdon-Davies phonophoric receiver, or other
instrument, for example, that shown in Figure 8, whereby the vibrations are
enabled through a relay to work Morse or other telegraph instruments.
I may use this plan of magnification as a call, or as a receiver in magnetic
telegraphy, but it is obviously applicable to other useful purposes such as magnify-
ing a speaker's voice by distributing it to various parts of a large hall.
The main features of the microphonic relay or magnifying telephone are shewn
in detail in Figures 2 and 3, where the vibrating carbon is in light contact (it
is shown separated in the figures for clearness) with another piece of carbon or
other electric conductor h which is firmly held and adjusted by a thumb screw i
working in a suitable support j. It is to be understood that the support j and the
spring or the prong of the tuning fork bare to be connected to a local battery
circuit which shall also be connected either directly or through a transformer with
the coil of another second receiving telephone. This second telephone thus sup-
plied with intermittent or alternating currents of magnified intensity may be a
telephone of ordinary pattern, or it may be a vibratory coil telephone like Figure 1,
or it may be another relay telephone like Figures 2 and 3 or like Figure 7 which
then in turn magnifies further and operates another telephone, and so on.
Figure 6 serves to show the connexions for such a series of magnifying tele-
phones, or telephone relays. In that figure the coil and condenser indicated at A B
represents subject matter described in the Specification of another Application for
Letters Patent filed by me and numbered 29,505 dated 13 December 1897, though
it may be replaced by any other transmitting or collecting apparatus: for instance
this original current fluctuator might be an ordinary microphonic transmitter
operated by the voice. The Roman numerals I, II, III and IV represent a possible
arrangement of the receiving and magnifying apparatus. No. I is a relay telephone
like, Figure 2 or Figure 3 with a vibratory coil varying the microphonic contact
of. the carbons d¹¹ and h, one of them being supported by the spring b. No. II is
another relay telephone like Figure 7 adapted to stronger currents, with its
vibratory coil varying the microphonic contacts in a granular transmitter with its
thin carbon diaphragm d'and carbon base . No. III is a loud-speaking.tele-
phone consisting of a vibratory coil and sound board, like Figure 1. No. IV
represents another form of loud-speaking telephone, alternative to the last, where a
vibratory diaphragm disturbs the outer air through a concentrating funnel. The
magnet in Nos. I II and III is supposed to be an electromagnet shaped like
Figure 4, but with only a single air gap surrounding the central shaft Co which
is wound with a magnetizing helix and surrounded by an outer iron cylinder
instead of the four rods c¹ of that figure. The magnet of No. IV is supposed to
be more like the horseshoe pattern of Figures 5 to 5º; or it may be any known
form of loud-speaking telephone. Electrical connection between I and II and
between II and III is effected by means of the transformers k, and k₁; and
are the local batteries, of which 7, is permissibly stronger than 1, because of the
many contacts in the granular microphone d¹¹. Instead however of the speaking
telephone No. III a modification called a "call telephone" may be employed. The
design of this is depicted in Figure 8 where the coil, suspended as before in a field
due to the magnet c by the rigid light connector e, operates the limb of a spring
or of a tuning fork 61 clamped to the pillar n and carrying an adjustable counter-
poise o for the purpose of equalizing the load on both prongs, and also permitting
a slight range of tuning. The studs p and q are platinum, lightly in contact, the
upper one being held by the thin spring and adjusted by the thumb screw i.
The pillar supporting this spring is insulated, as for instance by the ebonite s,
and thus and can be connected to a local battery circuit containing an ordinary
relay, the tongue of which is just held over by the current across the junction p, q
so long as that junction is undisturbed. But directly the fork trembles, the
contact between p and q is practically broken or greatly enfeebled, by the dancing
of the light spring on the heavier spring 6', and accordingly the tongue of the

page_text: relay in circuit with p, q (that is with a, j) moves over and completes the circuit
of an ordinary electric, bell or it may work a Morse instrument.
For the purpose of discriminating between a number of "call" stations a com
bination of differently attuned forks or tone telephones may be arranged, instead
of one, so that each shall respond strongly only to its own note and thus indicate
the particular station which is desiring to signal. The receiving or collecting
circuit may likewise be attuned to a definite note, as detailed in the specification
of my said prior application.
Whether the spring 6 or the tuning fork is employed as the elastic support
for the coil in any case is optional, but whenever precision of tuning is desired,
so that the receiver shall respond to one particular frequency of distant impulses
and not to others, I prefer the tuning fork; and in that case it would be preferable
to make Nos. I, II and III of Figure 6 all tuning-fork telephones. But where
many notes, or where speech is desired to be received and magnified, then either
a spring or a diaphragm or some other elastic support can be used. Further I find
that a microphone acts best when a certain strength of current is passing through
it; so whenever the receiving telephone is of too high resistance to permit this
strength of current to flow in simple circuit with it I shunt the telephone by means
of a low resistance self-induction or choking coil which conducts the main part
of the steady current but diverts the variations of current through the telephone.
On a long line a transformer is the natural mode of achieving this object but on
a short or purely local line I find the choke shunt preferable.
To enable a fairly strong current to be sent through a microphonic transmitter
without over-disturbing a 'telephonic receiver, I shunt the latter out by a self-
induction or choke coil t, as indicated in Figure 9, where the transmitter h¹ is
shown operated by one of the vibrating coils a as in Figure 7 but its telephonic
receiver is shunted by the coil t, whereby the steady current is mostly conveyed,
while its rapid fluctuations mostly go through the telephone. To assist the
fluctuation to go through the telephone, I place a condenser u in series with it as
shown in Figure 10. This has the effect of strengthening oscillations of some
particular frequency in especial, and of all frequencies not too far removed from that.
It is to be understood that the microphone transmitter may be worked by the
voice or by any other usual arrangement, and is not limited to the disturbance
by attached coils.
Whenever a temporarily inoperative microphone is in circuit with a telephone
(as for instance the ordinary transmitter belonging to a local receiver during the
reception of a distant message), an accidental noise, a grating or hissing; is usually
going on in the telephone. This can be diminished by shunting the telephone with
a condenser v, as indicated in Figure 11, an arrangement which is advantageous
in some forms of ordinary voice telephones, as it diminishes the disturbing noise
from the local transmitter while the desired message from a distant transmitter
is being listened to.
This and the other methods mentioned, though specially applicable to such
pure-tone-telephony as is appropriate for Morse signals, can also be used with
speech-telephony under certain conditions.
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. A telephone having a coil freely supported in a magnetic field upon an elastic
spring or its equivalent substantially as and for the purposes set forth.
2. In a telephone, the combination of a coil freely supported upon an elastic
spring or its equivalent with a magnet one pole of which is inside the coil while
the other pole is outside and surrounding it substantially as and for the purposes
set forth.
3. The method, substantially as set forth, of attaining forcible mechanical or
acoustic vibrations from fluctuating electric currents by a telephone consisting

page_text: 30
35
an elastically suspended movable coil, suspended in an annular
le magnetic field, and connected with a sound board, or its equivalent.
4. The method, substantially as set forth, of magnifying feeble mechanical
brations electrically received by means of a vibrating coil so arranged as to
perate a microphone or microphonic transmitter whose current serves to work
nother telephone.
5. The combination of a series of telephones and microphones connected alter-
ately electrically and mechanically, so that each telephone receives a disturbance
lectrically from the preceding microphone and passes it on mechanically in
magnified intensity to the next microphone, while each microphone receives a dis-
turbance mechanically from the preceding telephone (or in the case of the first of
the series possibly from the voice direct) and passes it on electrically to the next
telephone of the series.
6. The microphonic relay or magnifying telephone constructed substantially as
described with reference to Figures 2 and 3 of the accompanying drawings.
7. A magnet with one or more inter pole spaces each containing a suspende.l
coil of wire arranged to receive fluctuating currents and thereby to be thrown into
vibration substantially as described with reference to Figure 4, or to Figures 5,
5, 5", and 5 of the accompanying drawings.
call," a light metallic contact in a local relay circuit
8. As a telephonic
arranged so that it dances on an elastic vibrator and thereby changes in electrical
resistance when the vibrator is excited by means of fluctuating currents sent round
an attached coil suspended in a magnetic field substantially as described with
reference to Figure 8 of the accompanying drawings.
9. In a telephonic arrangement, the combination of a magnet, a mechanically
vibrating coil surrounding one of its poles, a microphone, and a telephone or its
equivalent substantially as and for the purposes set forth.
10. In combination, a tuning-fork or reed and a vibrating coil substantially as
and for the purposes set forth.
11. In combination, a tuning fork or reed, a vibrating coil and a loose contact
attached to the tuning fork for the purpose of operating a relay and so furnishing
a "call" substantially as set forth.
12. In a telephonic circuit the choke coil t substantially as and for the purpose
set forth.
13. In a telephonic circuit the condenser substantially as and for the purpose
set forth.
14. The combination, in a telephonic circuit, of the choke coil and the con
denser substantially as and for the purpose set forth.
Domber 1898.
Dated this 15th day
A. F. SPOONER,
323, High Holborn, London, Agent for the Applicant.