IMPROVEMENTS IN APPARATUS EMPLOYED IN ELECTRIC TELEPHONY
Year: 1883

page_text: LETTERS PATENT to John Henry Johnson of 47, Lincolns Inn Fields, in the
County of Middlesex, Gentleman for an Invention of "IMPROVEMENTS IN
APPARATUS EMPLOYED IN ELECTRIC TELEPHONY" communicated to him from
James Alvysius Maloney a person resident at Washington City in the District
of Columbia in the United States of America.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at
the Office of the Commissioners of Patents on the 20th March 1883.
JOHN HENRY JOHNSON, of 47 -Lincolns Inn Fields, in the County of Middlesex,
Gentleman, "IMPROVEMENTS IN APPARATUS EMPLOYED IN ELECTRIC TELEPHONY ".
A communication to me from James Alvysius Maloney a person resident at
Washington City in the District of Columbia in the United States of America
These improvements relate to both the transmitting and the receiving instru-
mentalities used in telephonic circuits
The improvement in the transmitting instrumentalities is characterised mainly
by the employment in a telephonic circuit of. a condenser which is brought into
action by the vibrations of the transmitter diaphragm in such manner that when
the transmitter (which is in the line circuit) is in use the condenser will discharge
intermittently to line with the effect of throwing onto the line a series of electrical
impulses which are transmitted to the receiving end-The condenser is in a local
charging circuit which is also completed through the transmitter.
The transmitter consists of a wooden box within which is a vertical thin wooden
partition having an opening in it, which is covered by a diaphragm consisting of
a thin sheet of metal applied to the front of the partition and secured thereto at
its upper edge-The diaphragm is provided on its opposite faces or at front and
back with a carbon tip or point-Opposite to the carbon tip at front is a carbon
point which is carried by an arm of spring metal pressed towards the diaphragm
by an adjusting screw-In like manner the other carbon tip at back is carried by
a spring metal arm which is pressed towards the diaphragm by an adjusting screw―

page_text: The rear of the box is provided with a door through which access can be had to the
adjusting screw in rear of the diaphragm; and the box is provided with a hinged
front door or false front (through which and the front wall of the box behind is
formed the voice opening) by opening which false front access can be had to the
front adjusting screw whose head projects outwardly into a recess, formed in the
front wall of the box-After the adjustments are effected both doors should be
closed and locked
Upon the box are three binding posts-The centre one is in electrical connection
with the diaphragm; one of the other posts is connected electrically to the front-
carbon tip; and the remaining post is electrically connected to the rear carbon tip
With a transmitter organised on this general plan are combined a battery,
condenser and telephone receiver, the circuit connections being such that botli the
circuit through which the battery charges the condenser and the circuit through
which the condenser discharges to line are completed through the transmitter.
I will describe two stations connected in accordance with this system-Each
contains a transmitter, a battery, a condenser and a receiver-The circuit connections
are as follows: Tracing first what may be termed the charging circuit, which is
the local circuit at each station through which the condenser is charged from the
battery one pole of the battery is carried to earth the other pole is connected by
a conductor to the front binding post, thence the circuit is made through the front
carbon tips, the diaphragm and its binding post, a conductor, and the condenser
to earth The carbon tips at front are so adjusted that normally they have full
and complete contact; and through the circuit thus completed the condenser is
charged from the battery
The line circuit may be traced as follows; starting from say the left hand
station-One pole of the condenser is carried to earth and the connection from
the other pole is carried through the conductor and post thence through the
diaphragm and rear carbon tips and the binding post in connection therewith to
the receiver at the other station-say at the right hand-the line being connected
at this station to the corresponding binding post, the circuit thence being
completed through the rear carbon tips, the diaphragm, the front carbon tips, the
binding post in connection therewith and to earth
The user speaks into the transmitter in the usual way-The diaphragm is thereby¯
caused to vibrate-The normal adjustment of the parts is such that the front
carbon tips have full contact, while the rear carbon tips have only partial or
incomplete contact-When however the diaphragm is in vibration it necessarily
makes complete and full contact with one and the other alternately with the result
of alternately charging the condenser from the battery and discharging the
condenser to line, there thus being a series of electrical impulses transmitted over
the line wire with the result of reproducing the voice loudly and distinctly in the
receiver at the receiving station
.
The ordinary magneto-electrical call can be used in this system as follows:-
There are ordinary call boxes and the usual angle lever switches provided with
hooks upon which the receivers are hung-and which by the weight of the
receivers are caused to swing in a direction to close the circuit between the call
boxes, and to break the circuit between the transmitters-Each box has one pole
carried to earth and the other pole is provided with a conductor with which the
switch can electrically connect
In lieu of a magneto-electric call an ordinary battery call can be used. Under
these circumstances the call box "earths" would of course be dispensed with*
The second portion of these improvements, relates to the receiving telephone-
In this instrument the core of the electro-magnet is a hollow cylindrical soft iron
shell which is slit lengthwise from end to end-the contiguous edges bounding the
slit being out of contact with one another-A core having these characteristics
acts to reproduce the voice with great distinctness, and renders the instrument
sensitive and very efficient-Its efficiency may be further enhanced by forming in
the tubular slit. core a series of slits extending lengthwise from each end of the

page_text: core towards its centre-in length say about one third the length of the core more
or less This construction allows the core to be polarised and depolarised rapidly.
The case of the instrument is made of non-conducting material in two parts
screwed together and holding between them a metallic diaphragm and its rubber
washer-The front part has the opening to which the ear is applied, termed the
ear trumpet; and it is made hollow to receive the electro-magnet, which consists
of a coil of insulated wire wound on a wooden spool or bobbin in the usual way-
the coil being electrically connected to line, through binding posts with which its
two ends are respectively connected-Within the bobbin is the tubular soft iron
core, which has the form of a cylindrical shell longitudinally slit on one side from
end to end.
According to a modification, the metal sheet from which the core is made is
preliminarily divided at its ends into a number of narrow strips or teeth by a series
of slits which extend from each end for about one third the length of the sheet-
The length of the teeth may be varied, but in practice the best results on the whole
are obtained with the length stated
The sheet thus preliminarily formed is bent or rolled up into the form of a
tube and in this way a tubular core is produced, having, as in the other instance,
the longitudinal slit but also having in addition ends composed of strips.
This core is to be adjusted and used in the same manner as the core herein before
described

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Henry Johnson in the Great Seal Patent Office on the
20th September 1883.
"
JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman "IMPROVEMENTS IN APPARATUS EMPLOYED IN ELECTRIC TELEPHONY
a communication to me from James Alvysius Maloney a person resident at
Washington City in the District of Columbia in the United States of America.
These improvements relate to both the transmitting and the receiving instruments
used in telephonic circuits.
The improvement in the transmitting instrument is characterized mainly by the
employment in a telephonic circuit of a condenser which is brought into action by
the vibrations of the transmitter diaphragm in such manner that when the trans-
mitter (which is in the line circuit) is in use, the condenser will discharge
intermittently to line with the effect of throwing into the line a series of electrical
impulses which are transmitted to the receiving end. The condenser is in a local
charging circuit which is also completed through the transmitter.
In the receiving instruments constructed or arranged according to this Invention
the core of the electro magnet is a hollow cylindrical soft iron shell which is slit
lengthwise from end to end the contiguous edges bounding the slit being out of
contact with one another. A core having these characteristics acts to reproduce
the voice with great distinctness and renders the instrument sensitive and very
efficient. Its efficiency may be further enhanced by forming in the tubular slit
core a series of slits extending lengthwise from each end of the core towards its
centre in length say about one third the length of the core more or less. This
construction allows the core to be polarized and depolarized rapidly.
And in order that the said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
I will first describe the transmitter. Figure 1 is a vertical central section from
front to rear. Figure 2 is a section taken on the line x x Figure 1 (the front
contact point being removed) and Figure 3 is a front elevation of the transmitter
constructed or arranged according to this Invention Figure 4 is a diagramatic
representation of two stations and their circuit connections.
Figure 5 is a sectional representation of the transmitter similar to Figure 1
placed in proximity to Figure 4 in order that the circuit connections may the more
conveniently traced in connection with the circuits shown in Figure 4.
The transmitter (Figures 1, 2, and 3) consists of a box A of wood or other
suitable material within which is a vertical thin wooden partition a having an
opening 6 in it, which is covered by a diaphragm B consisting of a thin sheet of
metal, applied to the front of the partition a and secured thereto at its upper edge.
The said diaphragm B. is provided on its opposite faces or at front and back with a
carbon tip or point c¹ d'. Opposite to the carbon tip c³ is the carbon point c which
is carried by an arm c² of spring metal pressed towards the diaphragm B by an
adjusting screw c³ In like manner opposite to the other contact point d' is the
carbon point d carried by a spring metal arm d² which is pressed towards the
diaphragmn by an adjusting screw d³-The rear of the box A is provided with a
door A through which access can be had to the adjusting screw d³ in rear of the
diaphragm, and the box is provided with a hinged front door or false front A²
(through which and the front wall of the box behind is formed the voice opening A³)
by opening which false front access can be had to the front adjusting screw c³
whose head projects outwardly into a recess (indicated by dotted lines at e Figure 1)
formed in the front wall of the box-After the adjustments are effected both
doors A¹ A should be closed and locked,

page_text: Upon the box A are three binding posts B₁ C. and D The centre one B' is in
electrical connection with the diaphragm B. the post C is connected electrically to
the front carbon point c as indicated in Figure 3 and the post D is electrically
connected to 'the rear carbon point d as indicated in Figure 2.
With a transmitter organised on this general plan are combined a battery,
condenser and telephone receiver, the circuit connections being such that both the
circuit through which the battery charges the condenser and the circuit through
which the condenser discharges to line are completed through the transmitter.
Figure 4 represents diagramatically two stations connected in accordance with
this system Each contains a transmitter A a battery E a condenser F and a
receiver G. The circuit connections are as follows.
Tracing first what may be termed the charging circuit, which is the local circuit.
at each station through which the condenser is charged from the battery, one pole
of the battery E is carried to earth and the other pole is connected by conductor 1
to the front binding post C, thence the circuit is made through c. c' B. B¹ conductor
2 and condenser F to earth. The points.c c¹ are so adjusted that normally they
have full and complete contact; and through the circuit thus completed the condenser
is charged from the battery.
The line circuit may be traced as follows, starting from the left hand station,
One pole of the condenser is carried to earth and the connection from the
other pole is carried through the conductor 2 to post B₁ thence through B, d, d'
and D, to line 3 and the receiver at the other (right hand) station the line at this
station being connected to the binding post D the circuit thence being completed
through d d B c c C, 1, through the battery E to earth.
The user speaks into the transmitter in the usual way. The diaphragm B is
thereby caused to vibrate. The normal adjustment of the parts is such that the
carbons c c¹ have full contact while the carbons d d have only partial or incomplete
contact. When however the diaphragm is in vibration it necessarily makes
complete and full contact with one and the other alternately with the result of
alternately charging the condenser from the battery and discharging the condenser
to line, there thus being a series of electrical impulses transmitted over the line
wire with the result of reproducing the voice loudly and distinctly in the receiver
at the receiving station. In Figure 4 is also indicated the manner in which the
ordinary magneto-electrical call can be used in this system.
H represents ordinary call boxes and I represents the usual angle lever switches
provided with hooks upon which the receivers are hung-and which by the weight
of the receivers are caused to swing in a direction to close the circuit between the
call boxes, and to break the circuit between the transmitters. Each box has one
pole carried to earth and the other pole is provided with a conductor with which
the switch I can be brought into electrical contact.
In lieu of a magneto electrical an ordinary battery call can be used in which
case the call boxes would be connected to the batteries as indicated by dotted
lines 4. Under these circumstances the call box "earths" would of course be
dispensed with. I will now describe the second portion of these improvements
relating to the receiving instrument.
Figure 6. is a longitudinal central section of a receiving instrument constructed or
arranged according to this Invention.
Figure 7 is a section taken on the line x x Figure 6 and Figure 8 is a section
taken, on the line y y Figure 6. Figure 9 is a perspective view of the instrument.
Figure 10 is a perspective view of the diaphragm and its rubber washer. Figure 11
is a side elevation of the electro-magnet-Figure 12 is a perspective view of the
tubular longitudinally slit core, Figures 13 and 14 represent a modification of the
core, Figure 13 shewing in plan the flat metal sheet and Figure 14 showing in
perspective the core made by bending the sheet into a cylindrical form.
The case of the instrument is made of non conducting material in two parts A. B
screwed together and holding between them the metallic diaphragm C and its
rubber washer a. The front part A has the opening 6 to which the ear is applied

page_text: termed the "ear trumpet" and the said part A is made hollow to receive the electro
magnet D which consists of a coil of insulated wire wound on the wooden spool or
bobbin c in the usual way, the coil being electrically connected to line, through the
binding posts d e with which its two ends are respectively connected as indicated
by dotted lines 1 and 2 in Figure 7. Within the bobbin is the tubular soft iron
core E, which as shown in Figure 12 has the form of a cylindrical shell longi-
tudinally slit on one side from end to end as indicated at f. In Figure 6 (for the
purpose of showing the parts more plainly) the inner end of the core is represented
as separated by quite a space from the diaphragm C but in actual practice it is set up
considerably nearer to, and in fact just out of contact with, the said diaphragm—in
which adjusted position it is maintained by any suitable means. According to a
modification represented in Figures 13, 14 the metal sheet from which the core E is
made is preliminarily divided at its ends into a number of narrow strips or teeth g
by a series of slits which extend from each end for about one third the length of
the sheet. The length of the teeth may be varied, but in practice the best results
on the whole are obtained with the length stated.
The sheet thus preliminarily formed is bent or rolled up into the form of a tube
as indicated in Figure 14, and in this way a tubular core is produced, having as in
the other instance, the longitudinal slit ƒ but also having in addition ends composed
of strips g.
This core is to be adjusted and used in the same manner as the core shewn in
the other Figures.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and, original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is :-
First In a telephonic circuit the combination with the receiver and the
transmitter of a condenser arranged and operating to intermittently discharge to
line through the diaphragm of the transmitter when the latter is in use substantially
as hereinbefore set forth.
"
Second-The combination of the transmitter, receiver, battery, condenser, and
circuit connections, substantially as described. whereby both the circuit through
which the battery charges the condenser and the circuit through which the
condenser discharges to line are completed through the transmitter.
Third A telephonic transmitter constructed substantially as hereinbefore
described with reference to Figures 1, 2, and 3 of the accompanying drawings.
Fourth In a receiving telephone the combination with the diaphragm of an
electro magnet provided with a tubular longitudinally split soft iron
substantially as and for the purposes hereinbefore set forth.
core
Fifth In a receiving telephone the combination with the diaphragm and the
ear trumpet of an intermediate electro magnet provided with a tubular longi-
tudinally split soft iron core which constitutes the communicating passage from the
diaphragm to the ear trumpet substantially as herein before set forth.
Sixth The electro magnet core E consisting of a soft iron cylindrical shell
having the longitudinal slit f and divided ends g substantially as and for the
purposes herein before set forth.
In witness whereof I the said John Henry Johnson have to this my
Specification set my hand and seal this first day of September One thousand
eight hundred and eighty three
J. HENRY JOHNSON (L.S.)