IMPROVEMENTS IN CYMAPHENS OR APPARATUS FOR TRANSMITTING SOUND BY ELECTRICITY
Year: 1881

page_text: LETTERS PATENT to Cromwell Fleetwood Varley of Bexley Heath in the
County of Kent and Frederick Henry Varley of Mildmay Grove, in the
County of Middlesex for an Invention of IMPROVEMENTS IN CYMAPHENS
OR APPARATUS FOR TRANSMITTING SOUND BY ELECTRICITY
PROVISIONAL SPECIFICATION left by the said Cromwell Fleetwood Varley
and Frederick Henry Varley at the Office of the Commissioners of Patents
on the 27th December 1881.
CROMWELL FLEETWOOD VARLEY of Bexley Heath in the County of Kent,
and FREDERICK HENRY VARLEY of Mildmay Grove in the County of Middlesex,
"IMPROVEMENTS IN CYMAPHENS OR APPARATUS FOR TRANSMITTING SOUND BY
ELECTRICITY."
The first part of the Invention may be described as a diaphragm microphone.
From the diaphragni proceeds axially a light rod or style. This style projects
through a carbon or other suitable rod-On the end of the style there is a spring,
preferably adjustible, which presses a cross bar or bars against a contact piece or
pieces. To the cross bar or bars, a piece or pieces of iron or suitable magnetic
inetal is or are attached.-The latter acted upon by an adjustible magnet or
magnets or other suitable means to regulate the pressure of contact between the
cross bar or bars and the contact piece or pieces. The cross bar or bars is or are
sometimes made in the form of a V or a crescent.-In some cases the cross bar or
bars or contact piece or pieces is or are attached to the style. One or more
suspended contact pieces are attracted by means of a magnet or pulled by a spring
or springs, so as to hang freely.-By moving the magnet or spring, the contact
piece or pieces is or are moved forward so as to touch the cross bar or bars.-These
arrangements permit of the use of very light microphone or contact bars which
move with great rapidity, and in consequence increase the amplitude and control of
the electric waves. In some cases the cross bar or bars to which the piece or

page_text: pieces of iron is or are attached is or are suspended inside a hollow helix without
touching it. This helix forms part of the microphone circuit, and variations in
the resistance at the point of contact vary the strength of the current in the
helix, and this acting upon the piece or pieces of iron which is or are placed
near armatures or magnets alter the variation of the resistance at the point of
contact, and so augments the amplitude of the electric waves.-Instead of
employing the helix, an electro-magnet may be included in the microphone
circuit. In front of each electro magnet, an armature is suspended.-The armaturo
carries a carbon or other suitable contact piece or pieces, pressing upon a small
fixed but adjustible contact piece or pieces. The armature and contact pieces also
form part of the circuit.-Any augmentation of the amplitude of the electric waves
due to the first described cross bar or bars produces a corresponding variation of
contact pressure due to the electro-magnet, which in turn, further augments the
variation of the resistance of the circuit, and so augments the amplitude of the
electric waves. In the local circuit is included the primary wire of an induction
coil.
The currents induced in the secondary wire are transmitted through the line
wire or wires to the receiving instrument. Another plan of effecting this purpose
which need only have one contact to produce the augmentation of the variation of
wave-amplitude is constructed as follows:-
The style upon the diaphragm passes through a hollow electro magnet or helix
forming part of a local circuit.-This style presses against an armature which latter
carries the contact piece of variable resistance.--Any variation of the force of the
electric-current varies the power of the electro magnet, and its attraction-upon-the¯|
armature. This latter_adds-to-or-takes from the pressure of the contact pieces,
producing a still further augmentation of the wave amplitude.-To obtain complete
control over the amount of augmentation of the wave amplitude, the electro-
magnet should be powerful in the first instance,-a series of shunts or sections of
the coil are attached to the electro magnet and by means of a rotatory or sliding
contact spring, these are included in or excluded from the magnetic circuit.
Another mode of augmenting the variation of the amplitude of the electric waves
consists of passing the current from the battery through a Christie balance or
electric parallelogram; one or more of the four arms consists of an electro magnet
with armatures and carbon contacts.-Suppose two of the arms to have such
contacts, then the one is made to increase the resistauce while the other decreases
it. This is effected by placing the relative variable contacts on opposite sides of the
respective armatures; this produces in the bridge powerful variations of current.―
The bridge is the primary of an induction coil. Another method of effecting this
augmentation of the variation of the wave amplitude is to hang a piece of carbon
or other suitable conductor from a spring or pivots.-This conducting piece rests
against the style projecting from the diaphragm, and also against a contact piece
mounted on a spring. When the style contact pressure increases, the spring
contact pressure decreases;-the hanging contact piece is attached to one pole
of the battery, the other pole being connected through two poles forming a
Christie balance.-This we call the "balance method;" or the two coils may formi
two primary wires around one iron core, the currents being made to flow in
opposite directions; this latter we call the "differential method." The receiving
instrument consists of a diaphragm.-The diaphragm has a coil of insulated
wire placed near to it.-There is a core, preferably adjustible inside it.-
Around this coil are placed several other coils the cores of which are in contact
or nearly in contact with the diaphragm.-The cores of the surrounding coils like
the centro coil may be magnetized, either by permanent magnets or by an electric
current. In this arrangement the diaphragm is highly magnetized from the margin
towards its centre.-In another form some or all of the coils are wound with two
separate wires the primary wire is connected with a local battery, to magnetize the
whole, the secondary wire is made part of the line circuit.-Instead of the
surrounding coils, a ring of iron may be placed near the disc or touching it, instead

page_text: of the surrounding magnets.-This ring is magnetized by a coil or coils of wire, or
by permanent magnets. Another improvement consists in cutting the ring
partially through axially so as to form a number of springs.-These are sprung
inwardly until the diaphragm is attached to them, they are afterwards liberated
and stretch the diaphragm. The diaphragms are generally first planished and then
electro plated, or coated with nickel.-In another form, a disc of iron or suitable
metal is attached to the ring.-In this disc there is a hole.-Behind this disc and
before the iron core of the central coil is placed a diaphragm of glass or other
suitable material which carries a piece of iron or other suitable material or a coil
of insulated wire which forms part of the line circuit or secondary circuit.-If no
surrounding ring or permanent magnets be used, a flat coil of insulated wire is
placed against or near to this perforated iron disc to magnetize it by an electric
current. Instead of the perforated disc a funnel shaped mouth piece of iron or
magnetized steel, is used, a disc is attached to the small end of the iron funnel and
the intermediate space is wrapped with insulated wire and magnetized by a
current. Diaphragms made of pith, German tinder or the fleshy substance of a
fungus dried or of vulcanite sponge are in some cases employed-Between the
secondary wire and the line wire we prefer to insert a condenser or condensers.―
To equalize the signals, we place a condenser between the ends of the secondary or.
on each side of the variable contact pieces.-In another form of receiver, we employ
a bell chamber or cylinder made of resonating materials, such as glass, metal, wood,
cork, pith, German tinder or similar substances upon this chamber when the same
is a non conductor of magnetism we attach magnetic armatures, and by using
polarized or magnetic cores surrounded by wire, to react upon the armatures, sound
is produced. We also use a similar resonating chamber for actuating the microphone
or microphones.
We also construct the current regulator by attaching an iron or magnetisable
crook to a diaphragm carrying a piece of suitable metal or carbon. Against this
presses an adjustable contact. An electro magnet is placed behind the crook The
current from a battery passes from the crook through the contact piece then around
the electro magnet and either through the line circuit direct or through a primary
coil, the secondary of which is connected between the earth and the line.
Another method consists in placing the contact piece in front of the mouth.
piece between the speaker and the diaphragm,-in this case we place an electro
magnet or the prolongation of a permanent magnet-behind the diaphragm. This
magnet has a cup or curved cross bar of iron on its pole near its end and its edge
is in close proximity with or united to the edge of the diaphragm. A coil of wire
is placed around the prolonged end of the magnet. Where a permanent magnet is
used it is made by preference to repel the diaphragm but the electric current
through the coil which forms part of the circuit reduces this repulsion and makes
the instrument very sensitive.
Where the line is joined direct to the current regulator the bell is connected at
one end between the battery and the line, at the other end between the line and
the earth or return wire. By this means the battery is only required to be at one
station. A key to break the bell circuit enables eather station to call the other.
We sometimes insert a condenser between the line and the current regulator at one
or both stations. A film of skin, prepared paper, caoutchouc or other suitable
material may be placed over the mouth piece to prevent the condensation of,
moisture upon the contact piece or diaphragm. This film takes off the roughness.
of the sounds transmitted and improves the clearness of the articulation
J

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Cromwell Fleetwood Varley and Frederick Henry Varley in the
Great Seal Patent Office on the 27th June 1882.
CROMWELL FLEETWOOD VARLEY of Bexley Heath in the County of Kent
and FREDERICK HENRY VARLEY of Mildmay Grove in the County of Middlesex
"IMPROVEMENTS IN CYMAPHENS OR APPARATUS FOR TRANSMITTING SOUND BY
ELECTRICITY
"
Fig. 1 represents one mode of affixing the style E to a diaphragm d. This style
projects through a carbon or other suitable rod a. On the end of the style thero
is an adjusting nut for regulating the pressure spring b which is made to press the
cross bar a against the contact pieces c. c'. To cross bar a an armature f, made of
iron or other suitable magnetic metal is attached. Near to this armature the poles
N and S of an adjustible magnet are placed; these poles attract the armature and
counteract the force of the spring b. It is obvious that if the magnet is of sufficient
force, it would overcome the pressure of the spring b, and open the circuit between
c and c¹-If the space between armature f and the poles N and S be increased the
magnetic force is weakened, and the spring b forces the cross bar a into contact
with c and c-thus by regulating the distance of the magnet n. 8. and the force of
the spring b, any degree of contact pressure can be produced, and the most sensitivo
condition for transmitting sound by means of electric waves obtained.
Fig. 2, shows the cross bar made in the form of a.crescent.
Fig. 3, shows the cross-bar or contact piece a attached to the style E.
Fig. 4. shows one method by which a singlo contact diaphragm microphone is
constructed N is the pole of a magnet, to which is attached a movable arm n
which carries the contact piece a. This arm is a movable prolongation of the
magnetic pole N. It is obvious therefore that if the diaphragm d made of iron,
steel, or nickel is moved toward n the attraction between the diaphragm and the
magnetized arm is more powerful, increasing the pressure between a and c, whilst
if the diaphragmn is caused to recede, the pressure decreases-Thus the vibration.
of the diaphragm d is made to convey by means of magnetism the corresponding
variation of pressure contact.
Figs. 5 and 6 show a microphone transmitter in which the cross bar a is fixed to
the diaphragm by a stile E as in Fig. 3. The contact pieces c, and c¹ are free to
move, being supported by a light movable swing piece g. g. to which is attached an
armature By adjusting the distance of the horse shoe magnet n. s the contact
pressuro is regulated to the required degree of sensitiveness to respond to the
vibration of diaphragm. In order that the pressure between a and c c¹ may be
equal, the swing piece g, g is mounted on a swivel pin passing through the
plate i, M is an adjusting screw for regulating the distance between the magnet
N. S. and the armature f
Fig. 5. shows the apparatus connected with an induction coil-A current from a
battery entering at K passes along the wire k to the contact c¹ thence across the
bar a to c¹, from thence through k to the primary of the induction coil o and out
at . On vibrating the diaphragm d electric waves pass through the primary
circuit and induce corresponding currents in the secondary wire the ends of which
are connected to the line terminals L and L' for completing the cymaphen
circuit.
Fig. 7. shows the cross bar a surrounded with an armaturef suspended inside
two coils on helices the circuit from the battery is made to pass through the
primary of the induction coil o through the helices p and q through c on to cross
bar a out at c¹ to the battery at .-The current flowing through the helices p. g
magnetize the armature fin the same direction as the poles of the magnet N. S. if
then the amount of current is reduced by lessening the contact pressure between a c
and c¹ by an inward movement of the diaphragm the magnet N. S exerts more

page_text: attractive force for the armature adding thereby to the movement set up in the
diaphragm d by increasing the pressure by an outward movement of the diaphragın
more current flows through the helices increasing the repulsion between the
armature and the magnet N. S. adding to the contact pressure and thereby
increasing the amplitude of the electric waves flowing through the cymaphen
circuit. Fig. 8. shows a form of electro magnet which we sometimes employ in tho
microphone circuit in place of the last described arrangement the current entering
at a passes around the core of the electro maguct and entering the terminal b
passes through the armature and contact piece o to the adjustable contact c¹ and
out at d-When therefore the contact pressure in the microphone increases tho
electro magnet becomes more powerful and in a like manner increases the pressure
between c and c' the reverse action taking place upon the lessening of current from
the microphone, thus any variation of the amplitude of the electric waves due to
the variation of contact pressure between a, the cross bar and contacts c and ci of the
microphone Figures 5 and 6 produces a corresponding variation of contact pressure
due to the electro magnet which in turn further augments the variation of the
resistance of the circuit and so augments the amplitude of the electric waves.
Figure 9 shews a similar arrangement but with the contact points reversed so
that an increase in the inagnetic effect shall reduce the pressure and not augment
it as described in reference to Figure 8. In the local circuit is generally included the
primary wire of an induction coil: the currents induced in the secondary wire are
generally transmitted through the line wire to the receiving instrument
Figure 10 shows another plan of effecting this purpose, requiring only one contact
to produce the augmentation of the variation of wave amplitude. The style E
upon the diaphragm d passes through the core of the electro-magnet p forming part
of a local circuit K and Ki. The style E. presses against the armature which latter
carries the adjustable contact piece c, of variable resistance any variation of the
force of the electric current varies the power of the electro magnet and its
attraction upon the armature f. This latter adds to the effect produced by the
movement of the diaphragm and adds to or takes from the pressure of the
contacts c. c. and in a like manner augments the wave amplitude to obtain complete
control over the amount of augmentation of the wave amplitude-The electro
magnet should be powerful in the first instance, a series of shunts or sections of
the coil are attached to the electro magnet p. and by means of the rotatory or
sliding contact spring these are included in or excluded from the magnetic
circuit
Figure 11 shews a simple method of producing the augmentation of the variation
of the current.
To the diaphragm D, is attached an iron crook C, making contact with Ci, which
latter is adjustible-The current from the battery passes through C to C, thence
through the coil K around the polo of the permanent magnet N. S. When the
diaphragm is pressed towards N. the contact pressure between C and Ci is
diminished The current which passes around K reduces its magnetic power.
When the pressure between C and Ci diminished, the current in K is diminished
and therefore the magnetism of N is increased and thus the amplitude of the
variation of the electric wave is augmented It is obvious that if the current
passing round K is too strong it will form a vibratory make and break.-Figure 11,
modified form of Figure 11 in which the contact is placed in front of diaphragm d.
the action being substantially the same as in Figure 11.
Figure 12 represents a form of cymaphen with electric wave augmenter which
possesses several advantages The battery + has one pole connected to the
earth or a return wire The other pole is connected to the iron hook i against
which presses the adjustible spring S. carrying contact pieces c. From 8, the
current passes around the coil K, on to the line wire through R. The current from
the battery bifurcates to the key or push p.-R. is an adjustible resistance coil
Y. a condenser is a bell constructed to ring when the circuit is broken-X is
an echo-cyme-vide C F Varleys Patent No. 1044 April 8th 1870 p G. line 28.

page_text: N. S. is a magnet preferably having a hollow pole-d is a vibrating plate. The
current on arriving at the distant station bifurcates part of it going through X. T.
to p, and thence to the return wire-The other portion goes through R around the
coil K to Si. through C and to pi and thence to return wire. The arrows show
the course of the current. In this arrangement the current around K weakens the
action of the magnet N. S. When the plate d is moved towards N the pressure
upon the contact pieces c is reduced consequently the current around K is reduced
and therefore the action of the magnetic pole N is increased, and so the electric
wave is augmented in strength by varying the resistance R. the right amount of
current around K is caused to flow-The condenser Y permits of the passage of
no continuous current, but it offers little or no obstruction to small rapid
undulations or variations of electro-motive force-The echo-cyme X. while allowing
a continuous current freely to pass is almost opaque to rapid undulations
consequently when the cymaphen plate d is caused to vibrate the undulations pass
with but very little more obstruction than that caused by the passage through the
coils K.-On pressing down the key or push p, the only current passing is that
through K and R the resistance of which latter is great and the bells T. Ti
immediately ring If the distant station presses down the key or push pi the
circuit is broken and the bells ring.
In this Figure a straight magnet is shown, but it is obvious that any other form
of magnet may be used.-In between K and Y a primary coil may be inserted
the secondary coil of which is connected to any form of telephone, such as Aders or
cymaphen
Figure 13. shows another form of carrying out-the-same principle-j is an iron
cylinder or an iron rod-or-there may be two or more,-The coil K² in this case is
-connected or wound in the opposite direction to that in Figure 12-so that the
current passing round the coil K" augments the strength of the pole N of the
magnet.
An important feature in this arrangement is that both the iron cylinder, and the
pole or poles of the permanent magnet are within the same coil and each is acted:
upon simultaneously-It it obvious to any experienced person that these forms
will work (though not so powerfully) without any permanent magnet at all.
Figure 14 shows a combination of these two plans by which a microphone de
works by production of pressure and yet the iron i. and the pole of the magnet N.
are within the same coil. In this Figure the coil K is not shown.
Figure 15. Another mode of augmenting the variation of the amplitude of the
electric waves consists in passing the current from the battery through Christie
balance or electric parallelogram. One or more of the four arms consists of an
electro-magnet with armatures and carbon contacts Suppose two of the arms to
have such contacts then the one as described in Figure 8 is made to increase the
resistance while the other (Figure 9) decreases it.-This is effected by placing the
relative variable contacts on opposite sides of the respective armatures. This
produces in the bridge powerful variations of current-The bridge forins the
primary of an induction coil O.-As the contact pressure of these variable
resistance A. and B. are under the control of the current from the microphone.
When the current from the microphone increases the resistance A. decreases whilst B.
increases This causes a change of potential which establishes a current through
K to K. The direction of current being dependent upon the relative resistances
A and B thus setting up a current in the secondary coil which flows through to
line at L and L'.-Another method of effecting this augmentation of the variation
of the wave amplitude is to hang a piece of carbou or other suitable conductor
from a spring or pivots.-(Figure 16). This conducting piece rests against the
style C projecting from the diaphragm and also against a contact piece mounted
on a spring C. When the style contact pressure increases the spring contact pressure
decreases.
The hanging contact piece is attached to one pole of the battery the other pole
being connected through two coils R R¹ forming a Christie balance-These latter

page_text: we call the balance method, or the two coils may form two primary wires around.
one iron core (Fig. 17) the currents being made to flow in opposite directions, this
latter we call the differential method; or two separate induction coils may be
employed The receiving instrument (Figs: 18 and 19) consists of a diaphragm d.
The diaphragm has a coil K of insulated wire placed near it. There is a core N
preferably adjustable inside it. Around this coil are placed several other coils K'
the cores of which are in contact or nearly in contact with the diaphragm d. The
cores of the surrounding coils like the centre coil may be magnetized either by
permanent magnets or by an electric current-In this arrangement the diaphragm
is highly magnetised from the margin towards its centre. In another form some
or all of the coils are wound with two separate wires; the primary wire is con-.
nected with a local battery to magnetize the whole-the secondary wire is made
part of the line circuit.
Figs. 20 and 21.
Instead of the surrounding coils a ring of wire may be placed near the disc or
touching it instead of the surrounding magnets as in Figs 18 and 19. This ring is
magnetised by a coil or coils of wire K or by permanent magnets. Another improve-
ment consists in cutting the ring partially through axially (Figs. 22 and 23) so
as to form a number of springs-These are spring inwardly until the diaphragm
is attached to them, they are afterwards liberated, and stretch the diaphragm-The
diaphragms are generally first planished and then electro plated or coated with nickel.
In another form partially shown as added to Fig: 20 at a disc of iron or.
suitable metal is attached to the ring . In this disc there is a hole or mouth piece-
behind this disc and before the iron core of the centre coil is placed a diaphragm of
glass or other suitable material which carries a piece of iron or other suitable
material, or a coil of insulated wire which forms part of the line circuit or secondary
circuit This application is shown more fully in Fig: 24 wherein two coils K K'
surround two magnetized hollow cores c¹. c.-These cores and coils carry the
diaphragm d, which may be of glass, to which is attached the small magnetized
disc d'. In front of or between dd the coil " is placed-Magnetic induction in
the core of the coil is effected by means of the vibratory discs dd which may be
regarded as movable prolongations of the poles N. S. The hollow cores admit of
hearing tubes H. H. being fitted therein as shewn-Cymaphen currents flowing
from . to k. produce sound equally from both, diaphragms which are conveyed
through the tubes H.
Fig. 25. shows the arrangement by which moving coils of wire are employed in
the place of discs aforesaid (Fig. 24). It consists of two central cores N and S.
passing through a non magnetic metal or stand N¹, and resting upon the magnet
n. 8. Around the central cores N and S. is an iron frame (see plan Fig. 26) which
is preferably constructed in the form of a spectacle frame the openings forming an
annular space between which the coils K. K work freely. The coils are supported
by balanced lever b to the extremities of which are attached arms bb, to carry
the diaphragms & which are weighted by the rings d' d. Currents flowing through
either of the coils K and K' cause the arm to oscillate, thereby communicating
motion to the centre of the suspended diaphragms d. d. Sonorous vibrations being
very rapid the diaphragm attached to each ring only responding to the sonorous
impulse, the inertia of the ring maintains the diaphragm in constant or uniform
tension. If no surrounding magnetising ring or permanent magnets be used a flat
coil of insulated wire is placed against or near to this perforated iron disc, to
magnetise it by an electric current. Instead of the perforated disc a funnel shaped
mouth piece of iron or magnetized steel is used. A disc is attached to the small
end of the iron funnel, and the intermediate space is wrapped with insulated wire,
and magnetized by a current as partly shown and described by reference to
Fig. 20. Diaphragms made of pith, German tinder or the fleshy substance of a
fungus dried or of vulcanite sponge in some cases employed. Between the
secondary wire and the line wires, we prefer it to insert a condenser or condensers.
To equalize the signals, we place a condenser between the ends of the secondary

page_text: or on each side of the variable contact pieces-Fig. 27. In another form of receiver
we employ a bell chamber 63 or cylinder made of resonating materials, such as
glass, metal, wood cork, pith, German tinder or similar substances-Upon this
chamber when same is a non-conductor of magnetism we attach magnetic
armatures ff, and by using polarised or magnetic cores N S. surrounded by wire
K' K to react upon the armatures, sound is produced. We also use a resonating
chamber for actuating the microphone or microphones. A film or skin, prepared paper,
caoutchouc or other suitable material, may be placed over the mouth piece to prevent
the condensation of moisture upon the contact piece or diaphragm. This film takes
off the roughness of the sounds transmitted and improves the clearness of the
articulation. Figs. 28 and 29, side and front elevation of variable resistance with
polarised cores- Figs. 30 and 31 front and side elevation of another form. Figs. 32,
33 and 34 side front and back elevations of a modified form, each with polarized
cores. Each of these Figs. show modifications of the variable resistances or
augmenters for increasing wave amplitudes as herein before described with reference
to Figs. 8 and 9-and their application as shown in Fig. 15.
1
Fig. 35 shows the circuit joined up with receiving cymaphen of same form as
shown in Fig. 2+. A represents the microphone and the receiving instrument.
A is usually made to contain the microphone induction coil and apparatus for
augmenting the wave amplitudes + and represent battery terminals L L', the
line circuit. When the arrangement shown and described in Figs. 12, 13 and 14
are not used, we arrange that a vibratory tongue in front of or near the end of core
of induction coil shall be set in action as a sonorous inake and break; and use the_
cymaphen receiving instrument A for the call instrument-instead of a bell, any of
the above described transmitting wave augmenting and receiving instruments may
-be combined for the purpose of our Invention. When the balance method before
described is employed they are similar connections. The local circuit flowing
through the microphone the arms and the variable resistance through the primary
circuit of the induction coil-The secondary being connected to the line or
cymaphen circuit by suitable connections.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed or carried out in
practice, We hereby declare that we claim
(1) The construction of microphones for sending cymaphen currents, substantially
as described and illustrated by Figs. 1, 2, 3, 4, 5 and 6.
(2) The use and application of variable resistances controlled by the microphone
currents for augmenting the amplitude of the electric waves, in the manner set
forth and described and illustrated by Figs. 7, 8, 9, 10, 15, 16 and 17.
(3) The combination as shown in Fig. 12 as and for the purposes described and
the modifications thereof in Figs. 13 and 14.
(4) The construction of receiving instruments substantially as shown and
described, with reference to Figs. 18, 19, 20, 21, 22, 23, 24, 25, 26 and 27.
(5) The combination in one instrument of microphone and variable resistance,
as shown in Figs, 7, 10, 11, 11ª, 12, 13, 14.
(G) The use of electro magnetic or polarised variable resistances as shown in
Figs. 8 and 9. and modifications thereof shown in Figs. 28 to 34.
In witness whereof I the said Frederick Henry Varley have hereunto set my
hand and seal this Twenty seventh day of June One thousand eight
hundred and eighty two.
FREDERICK H. VARLEY. (L.S.)