IMPROVEMENTS IN TELEPHONE TRANSMITTERS
Year: 1882

page_text: LETTERS PATENT to Richard Theiler and Meinrad Theiler, both of
86, Canonbury Road Islington, in the county of Middlesex for an invention
of IMPROVEMENTS IN TELEPHONE TRANSMITTERS
PROVISIONAL SPECIFICATION left by the said Richard Theiler and
Meinrad Theiler at the Office of the Commissioners of Patents on the
4th March 1882.
RICHARD THEILER and MEINRAD THEILER, both of 86, Canonbury Road,
Islington, in the county of Middlesex IMPROVEMENTS IN TELEPHONE
TRANSMITTERS
This invention relates to the construction of apparatus used for the electrical
transmission of articulate speech and known by the name of microphone. Such
apparatus invariably consists of two or more conductors of electricity in contact
with one another and to which vibratory motion is imparted by the voice or
other source of sound. This vibratory motion of the conductors produces a
vibratory current in the circuit connected thereto and thus the waves of sound are
converted into waves of electricity.
The novelty of our invention chiefly consists in the means used for communi-
cating the sound vibrations to the conductors and in the substitution of metallic
conductors for the carbon hitherto solely used in apparatus of this kind.
We use no tympanum or diaphragm to receive the sound vibrations and
communicate thein to the conductors, but cause the said vibrations to impinge
upon some fibrous or cellular substance such as cane, whalebone, pith, pinewood or
other material capable of readily transmitting sound. The shape of this substance
is immaterial; we prefer to make it cylindrical or cubical and to fix it in such
a way that the vibrations impinge upon one end or cross cut of the substance
while the microphone is attached to the other end or cross cut. By thus sub-
stituting a solid block or a bundle of either of the substances named for the tympan
or diaphragm used in other transmitters, we attain greater distinctness in the
articulation transmitted and by making use of the longitudinal vibrations of a

page_text: sound conductor instead of the lateral vibrations of a tympan or diaphragm, we
prevent a too violent agitation of the contacts and the breaking of the circuit
resulting therefrom. It is not necessary that the said sound conductor be a fixture;
it may be merely suspended.
Hitherto only carbon contacts were known to possess the property of varying
their conductivity in exact proportion to the amplitude of the vibrations imparted
to them and carbon was therefore necessarily used in all successful telephone
transmitters. After prolonged researches and experiments we have discovered that
metallic contacts made of Tellurium, Molybdenum or Manganese either pure or
alloyed with other metals possess the same property as carbon and we therefore
use any of the named metals or their alloys in the place of carbon for transmitting
speech electrically.
We also convert a contact of any metal instantly into a microphone by painting
it with an emulsion made of oil or other non evaporating fluid and finely powdered
coke dust, tellurium, molybdenum or manganese.
By connecting the conductors in the following manner we are enabled to make
a microphone that will transmit articulate speech almost of any metal or conducting
substance, the best conductors being the most suitable.
We cause one of the conductors, or two of them, to form part of a permanent
and unalterable electric circuit and then cause the free or suspended conductor in
contact with the fixed conductor or conductors to form a short circuit to the
battery. The action of this microphone consists therefore in the varying abstraction
of current from a closed circuit of unvarying conductivity while all other micro-
phones and so called tension regulators vary the resistance or conductivity of the
closed circuit and are capable of interrupting that circuit.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Richard Theiler and Meinrad Theiler in the Great Seal Patent
Office on the 2nd September 1882.
RICHARD THEILER and MEINRAD THEILER both of 86 Canonbury Road
Islington in the County of Middlesex "IMPROVEMENTS IN TELEPHONE
TRANSMITTERS"
This Invention relates to the construction of apparatus used for the electrical
transmission of articulate speech and known by the name of microphone. Such
apparatus invariably consists of two or more conductors of electricity in contact
with one another and to which vibratory motion is imparted by the voice or other
source of sound. This vibratory motion of the conductors produces a vibratory
current in the circuit connected thereto and thus the waves of sound are converted
into waves of electricity.
The novelty of our invention chiefly consists in the means used for communi-
cating the sound vibrations to the conductors and in the substitution of metallic
conductors for the carbon hitherto solely used in apparatus of this kind.
We use no tympanum or diaphragm to receive the sound vibrations and
communicate them to the conductors, but cause the said vibrations to
ange
upon some fibrous or cellular substance, such as cane, whalebone pith pine wor
other material capable of readily transmitting sound. The shape of this substance
is immaterial, we prefer to make it cylindrical or cubical and to fix it in such a way
that the vibrations impinge upon one end or cross cut of the substance while the
microphone is attached to the other end or cross cut.
By thus substituting a solid block or a bundle of either of the substances named
for the tympan or diaphragm used in other transmitters, we attain greater dis-
tinctness in the articulation transmitted and by making use of the longitudinal
vibrations of a sound conductor instead of the lateral vibrations of a tympan or
diaphragm we prevent too violent agitation of the contacts and the breaking of the
circuit resulting therefrom. It is not necessary that the said sound-conductor be
a fixture, it may be merely suspended.
Hitherto only carbon contacts were known to possess the property of varying
their conductivity in exact proportion to the amplitude of the vibrations imparted
to them and carbon was therefor necessarily used in all successful telephone
transmitters.
After prolonged researches and experiments we have discovered that metallic
contacts made of tellurium, molybdenum or manganese either pure or alloyed
with other metals possess the same property as carbon and we therefore use any
of the named metals or their alloys in the place of carbon for transmitting speech
electrically.
We also convert a contact of any metal instantly into a microphone by painting
it with an emulsion made of oil or other non-evaporating fluid and finely powdered
coke dust, tellurium molybdenum or manganese.
By connecting the conductors in the following manner we are enabled to make a
microphone that will transinit articulate speech almost of any metal or conducting
substance, the best conductors being the most suitable.
We cause one of the conductors or two of them to form part of a permanent
and unalterable electric circuit and then cause the free or suspended conductor
in contact with the fixed conductor or conductors to form a short circuit to the
battery

page_text: The action of this microphone consists therefore in the varying abstraction of
current from a closed circuit of unvarying conductivity, while all other microphones
and so called tension regulators vary the resistance or conductivity of the closed
circuit and are capable of interrupting that circuit.
In the drawings annexed Figures 1. 2. 3, 4. 5 and 6 shew the essential parts of
various forms of our telephone transmitter and the manner in which solid blocks
and bars of cane pith whalebone or pine wood are substituted for the tympans or
diaphragms of other telephone transmitters.
The instruments may be constructed in the dimensions of the drawings.
In Figure 1 A represents a cubical or cylindrical block of any of the substances
just now named, fixed to the case B of the transmitter in such a manner that one
end or cross-cut thereof faces the aperture C while the other end or cross cut carries
the microphone S.
The fine parallel lines represent the fibre or grain of the substance.
In order to prevent any but those vibrations which impinge directly upon the
said block through the aperture C from being communicated to the microphone S,
we insulate the block A accoustically from the case B by inserting some sheet
india rubber E, or other suitable material between A and B as shewn. The
india rubber is attached by means of cement to the surfaces with which it is
in contact.
In Figure 2 A³ is a bundle of sticks consisting of cane whalebone or pith bound
together to form the block for carrying the microphone. This bundle may be
secured by the two tapes or bands e, e¹, and it is fixed to the case B2 in the same.
manner as before described.
In Figures 3 and 4 the sonorous vibrations are caused to impinge upon a
suspended block, bar or slab D of cane or pine wood instead of upon a fixed block.
The parallel lines indicate the direction of the fibre.
We may construct the microphones or contacts attached to the vibrating blocks
in various forms, but prefer those shown by Figure 5 and Figure 6.
In Figure 5 the back of the block A in Figure 1 is shewn The two cylindrical
contacts b. b. are fixed to the vibrating block, each of them being connected to the
battery circuit in the usual manner, generally with an induction coil inserted as
shewn. The suspended contact d. completes the circuit by leaning against the
fixed contacts b. b'.
The air vibrations impinging upon the block A through the aperture C are
communicated to the contacts b. b'. and d. by the molecular vibration of the fibres
constituting the block A.
In the Drawing the contact d is represented as suspended from pegs projecting
from the back of the block A and this answers well, but adjustable hooks may
also be employed. The contact d. should be so set as to rest lightly against
the contacts b, b'
In Figure 3 the microphone contact f is placed as close as possible to the
suspension q while in Figure 4 this contact is placed as far as possible from
the suspension the fixed contact taking a different position in each case as
shewn.
The contacts in microphones used in the various forms of our transmitter shown
by Figures 1, 2. 3. 4 and 5 consist of solid pieces of tellurium molybdenum or
manganese, either pure or alloyed with other metals. We generally melt and cast
these metals in a suitable mould and cool the contacts thus made very slowly By
alloying these metals with silver platinum or gold we may increase the conductivity
of the contacts very greatly without destroying their microphonic property An
alloy of five parts tellurium and two platinum is very suitable. Equal parts of
tellurium and pure silver give very good results.-It is not necessary that both
contacts should consist of tellurium, molybdenum or manganese.
In the form of
microphone illustrated by Figure 5 we generally make only the suspended contact d.
of one of the metals just named, the fixed contacts being made of plainum.

page_text: When it is desirable to produce very loud articulation in the receiving telephone
and great sensitiveness is not required in the transmitter we construct the
microphone as shewn by Figure 6 and insert it into the block A³ as shewn.
This microphone consists of a small receptacle o, which may be a portion of glass
tube closed at the end by the two electrodes or contact surfaces of platinum or
brass p. pl. inserted therein but insulated from one another by shellac or other
suitable material. The metallic globules or granules h which are retained in place
by any suitable cover nearly fill this receptacle and close the circuit connected to
the contacts p p¹ more or less completely in proportion to the agitation imparted to
the globules.
As not all the globules or granules can break contact with one another and with
the electrodes p, p' at the same moment, this microphone possesses the advantage
that the most violent vibrations of the block A³ cannot produce an interruption of
the circuit.
The globules consist of tellurium, molybdenum or manganese and may be
produced in a manner similar to that in which shot is made. A mouth piece F
may in each case be provided.
We sometimes make all the contacts of a microphone of brass, copper silver or
any other metal and produce the microphonic action by painting the contacts with
a minute quantity of a paint made of any non evaporating liquid (olive oil or
watch oil is very suitable) and finely powdered tellurium, molybdenum, manganese
or coke.
Various telegraphic apparatus such as relays, keys and translators in which
there are metallic tongues in parts held in light contact by springs can be instantly
converted into telephone transmitters by painting the contacts with this emulsion
and making the necessary connections.
This semi-fluid microphone-contact produces a certain degree of adhesion which
prevents the easy interruption of the circuit.
Figure 7 shows in what manner we construct a microphone which acts upon a
different principle than the variation of resistance in the battery circuit.
The contacts g. g¹. which may be attached to a block as in Figure 1 form part of
the battery circuit Z. C, and primary circuit of an induction coil M in the manner
shewn.
It will be seen that this circuit is permanently closed and of an unalterable
resistance.
But as the suspended contact K which connects g with g¹. offers a shorter passage
to the current than through the induction coil M, only a part of the current
generated by Z. C, flows through M, such part varying with the more or less
intimate contact of K with g, g'. This microphone therefore acts as a "shunt"
abstracting more or less current from the primary circuit, while all other
microphones vary the conductivity of that circuit.
An interruption of the circuit is impossible with this arrangement and any
metal that is not readily oxidisable may be used for the contacts g, g¹. and K
We may vary the position or number of contacts shewn in the Drawing without
deviating substantially from the description of our invention herein given.
What we claim as our Invention is:
First. The construction of a telephone transmitter or microphone in which the
contacts are attached to a block of cane pith whalebone or pine wood or like
material as herein described and shewn by Figures 1. 2. 5 and 6.
Second. The construction of a telephonic transmitter or microphone in which the
contacts are attached to a suspended block of cane or like material as herein
described and shewn by Figures 3 and 4.
Third. The construction of a telephone transmitter in which the microphone-
contact is made by a piece or pieces of tellurium molybdenum or manganese
either pure or alloyed.
Fourth. The construction of a metallic microphone or telephone transmitter,

page_text: in which the microphonic action is obtained by a paint like mixture of a non
evaporating liquid and finely powdered tellurium molybdenum manganese coke
or other microphonic substance.
Fifth. The construction of a telephone transmitter or metallic microphone
connected in such a manner that the loose contact or contacts form a short circuit
to the battery, substantially as herein described and shewn by Figure 7.
In witness whereof I the said Richard Theiler have hereunto set my hand
and seal this twenty fourth day of August in the year of our Lord One
thousand eight hundred and eighty two.
MTOOT TO