Improvements in Microphones.
Year: 1898

page_text: Date of Application, 7th Mar., 1893
Complete Specification Left, 1st Dec., 1898- Accepted, 14th Jan., 1899
PROVISIONAL
SPECIFICATION.
Improvements in Microphones.
I, AUGUST HERMAN SKÖLD, of 32, Östgötagatan, Stockholm, in the Kingdom
of Sweden, Electrician, do hereby declare the nature of this invention to be
as follows:-
As the telephone finds a more extensive use the need is more keenly felt of
obtaining telphone apparatus which in their action are perfect and practically
independent of the length of the line circuit. The telephones hitherto employed
are influenced by the resistance of the line between the respective apparatus to
the current passed through it-the magnitude of this resistance having caused
the introduction of an induction coil for increasing the tension of the current and
thereby overcoming the resistance.
It has also been proposed to employ two spring-actuated contacts bearing upon
the diaphragm and located in series in the circuit, for the purpose of forming
several closing arcs and thus increasing the intensity of the current-fluctuations
and the distinctness of the speech.
This invention relates to an application of the latter arrangement to micro-
phones provided with contacts of granulated carbon with a view to overcoming
the resistance of long line-circuits without the aid of an induction coil, as referred
to above. The granulated carbon is contained in spaces separated from one another
by partitions of felting or other suitable material and so located with reference
to contact pieces on the diaphragm that the places of contact of the carbon spaces
and the diaphragm will be located in series in the line circuit in which no induction
coil need be used. In previous microphones provided with contacts composed of
granulated carbon, carbon rods, or equivalent means, the diaphragm forms only
place of contact with said contact-members.. The difference in strength of the
maximum and minimum current passed through said place of contact is thus
dependent on the extent of the movements of the microphone diaphragm. The
greater the pressure of the microphone-diaphragm against said contact is, the less
will be the resistance to the current, and the greater the flow of current passing
through the circuit and causing the attraction of the diaphragm of the receiver
to its magnet. As, however, in a long circuit the resistance may nearly equal or
even exceed that of the contact, the resistance of the circuit will decrease the
influence exerted on the electro magnet of the receiver by the current impulses
passing at the point of contact in the microphone there being therefore but a
slight difference in the influence of successive impulses and the sound becoming
indistinct or inaudible. The object of this invention is to obviate said difficulty
by increasing the difference of the maximum and minimum resistance of the
contact in the microphone in a manner previously known in microphones provided
with spring-actuated contacts and to thus decrease the influence of the resistance
in the line circuit.
The invention is carried out, as mentioned, by increasing the number of places
of contact in the microphone and arranging them in series in the same circuit
with the telephone receiver and at the same microphone diaphragm. As a result,

page_text: a local battery and an induction coil for a primary circuit will no longer be
needed for each microphone the current being sent from a battery or current
source in common to the whole line system to the electro magnets of the telephone
receivers. As these places of contact are located in series at the same microphone
diaphragm the resistance will be decreased or increased as many times, as com-
pared with the use of only one place of contact, as the number of such places of
contact employed i.e. the influence of the motion of the diaphragm will be as
many times greater as the number of places of contact used. The differences in
the strength of the current impulses transmitted being correspondingly increased,
the effect produced on the receiver diaphragm consequently will be more powerful.
In the line circuit provided with the battery there are successively inserted
carbon contacts located close to the same diaphragm inserted in the circuit. This
diaphragm is provided with insulated contact-plates that connect each two
adjacent carbon contacts, which are not continually in contact with each other, the
contacts being connected in pairs. As an example five places of contact may be
thus formed at the diaphragm, which are closed or opened simultaneously. By
multiplying the places of contact the resistance is decreased or increased as many
times as the number of contact-places exceeds one, as the diaphragm is approached
to or removed from the contacts, powerful vibrations of the receiver diaphragm
being thereby produced. In the instance chosen the difference between the most
powerful and the weakest attractions will be multiplied five times.
In this example the wire from the battery is attached to a screw-terminal or
contact-point connected with a carbon disc at the centre of the system of granu-
lated carbon contacts in the microphone. Outside of this carbon disc there are
two semi-circular carbon segments situated opposite four segment shaped spaces
which are separated from each other by strips of felting, each forming a quarter
of a circular ring. Two of the strips of felting thus enter only part way into the
carbon segments while the two others at right angles to the former enter fully in
between them insulating them from each other. They are all attached to a
base
disc of ebonite. At the side of the microphone diaphragm which faces the granu-
lated carbon contacts there are tin foil or metal leaf contact pieces insulated from
one another and from the diaphragm. It is evidently possible to vary the number
of said places of contact and their location in a number of ways without departing
from the characteristic features of the invention. Likewise, the places of con-
tact at the diaphragm, in place of being attached to the latter, may be situated
in its interior, i.e. form a part of it.
Dated this Seventh day of March 1898
JENSEN & SON,
77, Chancery Lane, London, W.C.,
Patent Agents.
11 днегорнопер.
I, AUGUST HERMAN SKÖLD, of 32, Östgötagatan, Stockholm, in the Kingdom
of Sweden, Electriciah, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:-
As the telephone finds a more extended use the need is more keenly felt of
obtaining telephone apparatus which are perfect in their action and practically
independent of the length of the line circuit. The telephones hitherto employed
are influenced by the resistance of the line between the respective apparatus to
the current passed through it, the magnitude of this resistance having caused the

page_text: ntroduction of an induction coil for increasing the tension of the current and
thereby overcoming the resistance.
It has also been proposed to employ two spring-actuated contacts bearing upon
the diaphragm and located in series in the circuit, for the purpose of forming
several closing arcs and thus increasing the intensity of the current fluctuations
and the distinctness of the speech.
This invention relates to an application of the latter arrangement to micro-
phones having one diaphragm, and I provide in connection therewith contacts
of granulated carbon, with a view to overcoming the resistance of long line-
circuits without the aid of an induction coil as referred to above. The granulated
carbon is contained in spaces separated from one another by partitions of felting
or other suitable material and so located with reference to contact pieces on the
diaphragm that the places of contact of the granulated carbon spaces and the
diaphragm will be located in series in the line circuit, in which no induction coil
need be used.
.
In previous microphones provided with contacts composed of granulated carbon,
carbon rods, or equivalent means the diaphragm forms only one place of contact
with said contact members. The difference in strength of the maximum and
minimum current passed through the said place of contact is thus dependent on the
extent of the movements of the microphone-diaphragm. The greater the pres-
sure of the microphone-diaphragm against said contact is, the less will be the
resistance of the current, and the greater the flow of current passing through the
circuit and causing the attraction of the diaphragm of the receiver to its magnet.
As however in a long circuit the resistance may nearly equal or even exceed that
of the contact, the resistance of the circuit will decrease the influence exerted on
the electro magnet of the receiver by the current impulses passing at the point
of contact in the microphone, there being therefore but a slight difference in the
influence of successive impulses so that the sound becomes indistinct or inaudible.
The object of this invention is to obviate said difficulty by increasing the
differences of the maximum and minimum resistance of the contact in a manner
previously known in microphones provided with Spring-actuated contacts and to
thus decrease the influence of the resistance in the line circuit.
The invention is carried out as mentioned, by increasing the number of places
of contact in the microphone and arranging them in series in the same circuit
with the telephone receiver and all at the one microphone diaphragm. As a
result, a local battery and an induction coil for a primary circuit will no longer
be needed for each microphone, the current being sent from a battery or current
source in common to the whole line system to the electro-magnets of the telephone
receivers. As all these places of contact are located in series at one and the
same microphone diaphragm, the resistance will be decreased or increased as many
times, as compared with the use of only one place of contact, as the number of
such places of contact employed i.e. the influence of the motion of the diaphragm
will be as many times greater as the number of places of contact used. The
differences in the strength of the current impulses transmitted being correspond-
ingly increased, the effect produced on the receiver diaphragm will consequently
be more powerful.
In the accompanying drawing Fig. 1 is a longitudinal section through such a
microphone apparatus shown as an example. Fig. 2 shews the arrangement of
the granulated carbon contacts, the diaphragm f being removed, and Fig. 3 is
plan view of the diaphragm from the speaking side, the places of contact at the
back or contact side being marked in dotted lines. Fig. 4 is a diagram shewing
line connections. From the latter it will be seen that in the line circuit provided
with the battery a there are successively inserted carbon contacts b, the latter
being here assumed to be located close to the same diaphragm c inserted in the
same circuit. This diaphragm is provided with insulated contact plates that
connect each two adjacent carbon contacts 6 which are not continually in contact
with each other, the contacts being connected in pairs. As an example five

page_text: pieces of contact are in this case formed at the diaphragm which are closed or
opened simultaneously. By multiplying the places of contact the resistance
compared with the use of only one place of contact is decreased or increased as
many times as the number of contact places exceeds one, as the diaphragm is
approached to or removed from the contacts, powerful vibrations of the receiver
diaphragm being thereby produced. In the example chosen the difference
between the most powerful and the weakest attractions will be multiplied five
times, compared with the case when only one place of contact is used.
In this example, shewn in Figs. 1, 2 and 3, the wire from the battery is attached
to a screw-terminal or contact point d connected with carbon disc e at the centre
of a group or system of granulated carbon contacts in the microphone. Outside
of this carbon disc there are two semi-circular carbon segments m and n situated
opposite four segment shaped spaces 9 and h and i and k respectively which are
separated from each other by strips of felting and 12 each forming a quarter of
a circular ring. The two felt strips thus enter only part way into the carbon
segments m and n while the two felt strips 13 at right angles to 1, 1, enter fully
in between them, insulating them from each other. The are all attached to a base
disc o of ebonite. At the side of the microphone diaphragm f which faces the
granulated carbon contacts there are tinfoil or metal leaf contact pieces pq and r,
insulated from one another and from the diaphragm f. The current from the
battery entering at the terminal d thus passes along the path epgmhqin kr
and thence through the diaphragm f and the microphone case and further to the
receiver and the battery. Places of contact will exist between e and p, p and 9,
h and q, q and i and k and r. It is evidently possible to vary the number of said
places of contact and their location in a number of ways without departing from
the characteristic features of the invention. Likewise the places of contact at the
diaphragm, in place of being attached to the latter may be situated in its
interior i.e. forming a part of it.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
1. In a microphone with one diaphragm the application and use of contact
pieces provided thereon or therein, in combination with a corresponding number
of contacts consisting of spaces containing granulated carbon, said spaces being
separated from each other by partitions, and the places of contact being located
in series in the circuit, for the purpose of increasing the intensity of the current
fluctuations and the distinctness of the speech while doing away with the necessity
for the use of an induction coil, substantially as set forth.
2. The construction of microphone described with reference to the drawings.
Batod
Bamat
1000
Batod at
TO
2000
ՈՐՈ
JENSEN & SON,
77, Chancery Lane, London, W.C.,
Patent Agents.