IMPROVEMENTS IN TELEPHONIC APPARATUS
Year: 1882

page_text: LETTERS PATENT to John Munro 2 Somerset Villas, West Croydon, Surrey,
and Benjamin Warwick 13 Highbury Hill London N. for an Invention
of IMPROVEMENTS IN TELEPHONIC APPARATUS
PROVISIONAL SPECIFICATION left by the said John Munro and Benjamin
Warwick at the Office of the Commissioners of Patents on the 27th July
1882.
JOHN MUNRO of 2 Somerset Villas West Croydon Surrey and BENJAMIN
WARWICK, 134 Highbury Hill London N IMPROVEMENTS IN TELEPHONIC
APPARATUS
Part consists in forming telephonic transmitters out of light metal fabrics such
as wire gauze, preferably tarnished. Two pieces of tarnished iron wire gauze kept
in contact under pressure by means of adjustible screws, weights, or magnets serve
to transmit the voice when spoken to direct or when enclosed in a sonorous caso
or mounted on a stand capable of vibrating. It may be protected from the rudeness
of the breath by a separate grating diaphragm or mouthpiece in front.
enclosed in a case the latter may contain air or other gas, or a fluent liquid having
When
no cleansing action on the metal:
Gauze of other metals, or other arrangements of tarnished wires may be used:
also gauze or wires in contact with a continuous conducting surface, of any shape.
Two light metal surfaces tarnished, burred, rasped, or otherwise roughened to give
numerous contact points also serve instead of gauze, as do conductive plates with
metals preferably tarnishable, deposited by any means in fine division on their
surfaces. Small metal grains or pellets preferably with conductive tarnish kept in
a case or grating also answer; those of iron being very effective.
These transmitters can be used either with or without an induction coil. To
soften the quality of the sound an electromagnet or other inductive resistance may
be inserted between the transmitter and the line. The same effect is produced by
immersing the transmitter in liquids; a device applicable to other transmitters.
[Price 6.1

page_text: The wire transmitter may also be enclosed in a vaccuum and in this case it may
take the form of fine metal points close to each other but not necessarily
touching.
These transmitters, especially those of iron, can be used as telephonic relays by
attaching them to the diaphragm of the receiving telephone so that its vibrations
affect the sensitive part of the transmitter in circuit with a local battery and the
other line.
To annul the disturbances due to the induction of signal currents on neighbouring
telegraph lines a signal key with carbon points is employed. Induction apparatus
between the telephone line and instruments also helps, as does a delicate vaccuum
discharger connected between this line and earth.
Another part of the invention is the use of the above or other transmitters for
The trans-
the detection of torpedoes or submarine vessels moving under water.
mitter is lowered under water, say from a boat, and is enclosed in a watertight
vibratory case, or left bare as the case may be. At a still depth it will detect the
vibration of the propeller of the submerged missile and announce its presence in a
telephone to the watch. The telephone and transmitter are connected through a
battery by a cable, and to reduce the inductive retardation in this and other
telephone cables the latter is preferably made of low insulation, either by artificial
leaks or a dielectric of low resistance.
The torpedo detector may also be utilized at sea for telling the distance to a
coast, ship, iceberg, etc, by striking a bell or making other sound under water and
noting the time before the water echo from the obstruction reaches the transmitter.
A vibrating reed, going by electromagnetism may give the sound.
A third part of the invention is for a telephone receiver made by sending the vocal
currents through fine metal wires attached by one end to a diaphragm, preferably
of mica and under tension so that their electric dilatation shall set the diaphragm
vibrating If the wires are bent into spiral form the electrodynamic attraction
is superadded. By using a thin metal diaphragm the wire may be wound into a
bowl shape and its bottom caused to attract the diaphragm itself. Another form
of receiver consists in passing the current through a set of microphonic joints
which by expanding and contracting vibrate a diaphragm in connection with
them.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Munro and Benjamin Warwick in the Great Seal Patent
Office on the 27th January 1883.
JOHN MUNRO of 2 Somerset Villas West Croydon and BENJAMIN WARWICK of
134 Highbury Hill N. IMPROVEMENTS IN TELEPHONIC APPARATUS"
We will now describe several types of our transmitters; but it is to be understood
that we do not bind ourselves to the precise forms illustrated as there are other
ways of producing the same effects by varying the details of construction.
Fig 1 is a section through one form of our wire transmitter, and fig: 2 is a plan
drawn on the line X Y. In fig 1 A is a case having a mouth piece M with a grating
across its lower end to prevent tampering g and glare two pieces of wire fabric or
grating such as iron gauze; g has a hole cut in it to allow a spring S from g¹ to pass
through and connect with an adjusting screw above. Wires W W connect the two
gauzes in circuit with the battery and line or with the primary of an induction coil I
whose secondary is connected to the line, in the usual way.
mouthpiece the air-waves pass through the gauze and agitate them so as to
On speaking into the
transmit the voice. Instead of a grating across the mouthpiece a sheet of match
board, or other vibratory substance may be used, and the mouthpiece prolonged
into a tube giving the best distance to speak from, as shewn in figure 3°. As it is
the Air waves themselves which agitate the sensitive part of the transmitter a
reflecting board may be employed to throw them down upon the gauze. Sounding
posts can also be used to improve the sonorous qualities of the Case. Fig: 4 is a
simpler form of this transmitter, the sound chamber being sinall, and the mouth-
piece horizontal. Thin metal plates with corrugated or roughened surfaces may
also be employed in place of the wire gauze.
Instead of a spring adjustment, a magnetic one may be applied, especially if the
metal used is iron. The pole of a bar magnet or an electro magnet brought to bear
on the sensitive contacts holds them together with a force corresponding to the
nearness of the pole which is adjustible by a screw. When an electro-magnet is
used, as shewn in figure 11° where m is the magnet B the battery and g g' the
metals the increase of current due to the
of the voice waves, causes the
magnet to increase its action in a corresponding degree, and enhance the effect.
The electromagnet may obviously be the primary and core of the induction coil
used. The pressure between the metals may also be regulated by gravity in an
obvious manner.
Fig 5 is a section of our bar type of transmitter and Fig: 6 is a plan of the metal
contacts Here A is a box with suitable mouthpiece as before, and B is a board
placed across the latter; b and b' are two blocks of metal, preferably of cast iron
either clean or tarnished and fastened to the board A third piece or bar bl
figure 6 of the same material is inserted into holes bored in the blocks and works
oosely on these. Wires W W' run from the blocks as shewn and connect in
circuit with a battery and the line or the primary of an induction coil I, The
microphonic contact between 6" and the two blocks b b¹ carrying it, is adjusted by
he spring
and regulating screw S.
Other adjustments may be applied to this form of transmitter; and instead of
aving two sensitive contacts, a number of these may be provided by multiplying
he blocks and bars. A matchboard or other diaphragm may be placed across the
uouth to ward off the rudeness of the voice, as in the wire transmitter, for it is
esirable to let the air-waves act as purely as possible on the delicate contacts.
The addition of suitable liquids, such as fine clock oil, to the joints is sometimes an
dvantage.

page_text: A thermo-electric microphone transmitter is made by adjusting two dissimilar
metals together for example two pieces of gauze, and heating the joint; while the
telephone is connected between the cold ends of the metals, in a manner readily
understood. These elements may be combined in series after the manner of a
thermo-pile; and the heat may be produced by the application of a flame, or the
electric current, or by radiant energy reflected from a mirror. Instead of applying
the sound waves direct to the microphonic contact we may also cause them to
vibrate the reflector, or the flame itself; as in the "radiophone."
:
Figs 7 and 8 are two forms of our grain or pellet transmitter in which metal
grains, either tarnished or untarnished are enclosed in a case between two metal
plate electrodes and agitates by the voice, while the current traverses them. In
fig: 7 A is a base board with an aperture in it which is lined on opposite sides with
metal electrodes bb' connected to Wires W W' as before. The back and front of
the aperture are armed with wire gauze or other metal fabric and the aperture is
filled with small grains, flakes, filings or pellets of metal, preferably of brass and
iron. The air-waves agitating these, cause the mass to transmit the voice. Fig 8°
is another form with a mouthpiece M, and an induction coil added in the usual
way. Matchboard may also be used with this transmitter, and the electrodes
may be plates or sheets of metal placed back and front, instead of the wire guaze
as above When the transmitter is closed in this way the grains may be immersed
in a suitable liquid to take the place of air. A liquid which is elastic, non-
conducting, non-viscous, and does not corrode the metal is the best. The action of
the liquid is chiefly to reduce the sensitiveness of the metal and prevent "buzzing,"
but it may also have a preserving effect on the metals. It is applicable to all
microphone transmitters. The liquid modifies the vibrations, and for this purpose
it may also be enclosed by itself in a case, B as shewn in figure 14 where M is the
microphone fixed behind. On speaking to the case, which may have thin metal
sides the vibrations are communicated in a modified form to the transmitter
behind.
:
39
Fig 9 represents our chain type and transmitter wherein A is a case with mouth-
piece M and a diaphragm to the centre of which is attached a metal chain, c,
ending in an adjustable spring S by which the tension of the chain can be regulated
in the ordinary manner. The chain is in circuit with a battery and the line, or
the induction coil I as before; and on speaking into the mouthpiece the vibrations
of the diaphragm modify the tension of the chain and transmit the voice.
Fig: 10 is an adaptation of our transmitters a telephone relay. Here E is the
electro magnet of the telephone receiver, g, is the iron diaphragm carrying a metal
transmitter (preferably of wire) in circuit with a local battery B and telephone T.
The vibration of the diaphragm are in this way transmitted to the local telephone.
Fig: 12 is a device for detecting torpedoes; A being a box with mouthpieces.M, M
on each side, each closed by an elastic diaphragm carrying behind it a microphone
transmitter T. These transmitters are connected through a cable c, with batteries,
telephones, and induction coils on board the vessel from which the detector is
lowered; and when the water waves due to the passage of a fish torpedo or sub-
marine boat strike the diaphragmus at M M the microphones announce the fact.
The microphones need not be placed on every side of the box and the box may
be filled with a suitable liquid such as Glycerine and water, to resist collapse, and
prevent "buzzing."
The cable usually employed by submarine messages has a high inductive
capacity which retards the transmitter currents, and we employ a special cable
consisting of two very fine metal wires, far finer than usually employed, and
separate then by a layer of good insulator. They may be side by side, or be
wound round each other, or one wire may be used and a fine tape of metal wound
round it after it receives its coat of insulator; but in every case our object is to use
wire of very small mass, so as to give small inductive surfaces. They must also be
very near each other compared to the other inetal near, such as the sheathing of the
cable This sheathing may be iron wires, or tape, or lead piping after the usual

page_text: manner; but the conductors it protects are to be separated from it by a considerable
thickness of insulator
Our receiving telephone is shewn in figure 13, where A is a case with mouth-
piece M and diaphragm c¹. A fine spiral of wire is attached to the diaphragm and
placed opposite a coil of wire c of equal diameter mounted on a screw S for
adjusting its distance from the diaphragm.
The
The line current may pass by wires W W, WI W¹, through both coil or spiral or
one may be excited by a local battery and the other by the line current.
Electro dynamic attraction between these sets the diaphragm in vibration.
Another form of Receiver shewn in figure 15° consists of an iron core C connected
to a diaphragm D in such a manner that the electrical torsion of the core due to
the current traversing it or a coil B surrounding it will cause the diaphragm to
vibrate, by means of a radial spine, p, rigidly fixed to one end of the core and
connected with the middle of the diaphragm by a thread t.
Having now described the nature of the said Invention, we claim
Firstly The combination of a current regulator formed of light conductors in
delicate contact and a sound chamber where the sound waves act either directly or
through the case on the regulator and vary the strength of current passing
through it.
Secondly The combination of light metal fabrics having conducting surfaces in
contact under pressure, and tarnished or untarnished, with spring, gravity, or
magnetic adjustments, and with a sound chamber and mouthpiece so arranged that
the air waves of sound can act directly or through the case on the contact without
the use of a pressure tympan or diaphragm.
Thirdly The several general forms of metal transmitters, either tarnished or
untarnished, and with or without liquids as setforth.
Fourthly The current regulators of wire gauze gratings, or rough metal surfaces
and of cast iron, for telephonic purposes substantially as described
Fifthly The use of liquids surrounding microphonic contacts for adjusting and
preserving purposes, substantially as described.
Sixthly The liquid vibrator to modify the sound waves, as setforth.
Seventhly The microphonic arrangement for detecting sub-marine noises and
disturbances substantially as described.
Eighthly The thermo-electric combinations as setforth.
Ninthly The receiving telephones substantially as described.
Tenthly The telephonic conductor of low inductive capacity substantially as
lescribed.
In witness whereof I the said John Munro on behalf of myself and the said
Benjamin Warwick have hereunto set my hand and seal this twenty seventh
day of January in the year of our Lord One thousand eight hundred and
eighty three.
JOHN MUNRO. (L.S.)