IMPROVEMENTS IN ELECTRIC TELEPHONE TRANSMITTERS
Year: 1884

page_text: "
Í JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN ELECTRIC TELEPHONE TRANSMITTERS a communication to me from abroad by
James Aloysius Maloney of Washington, District of Columbia in the United States
of America to be as follows:-
This Invention refers more particularly to a Telephone transmitter of the type
described in the Specification of Letters Patent No 1452 of March 20th 1883 but
in some respects it is susceptible of application to transmitters of other types.
The said Invention is directed mainly to an improved construction and arrange-
ment of the contact points through which the impulses due to the vibrations of the
diaphragm are transmitted to line and in this respect is characterized principally
by the combination with the diaphragm of a contact point a spring acting carrier
thorefor attached to and moving with the diaphragm and a controlling device
termed by the Inventor "stirrup" which bears upon the spring-carrier and during
the vibratory movements of the latter operates to direct its movements to and from
the stationary contact point in connection with which the carriers contact point
works. It also has to do with the Carbon contacts of Electric telephone transmitters
and other instruments in which microphonic contact is required the object being to
keep the microphonic contact unimpaired and to prevent the accumulation and
building up between the contacts of fine Carbon dust which results finally in
establishing a closed circuit between the contacts thus incapacitating the instrument
for efficient work. This object can be attained by interposing between the Carbon
contacts loose iron filings or other metal in a state of minute division, the easiest
way of practically carrying out this improvement being to place the Carbon
contacts vertically one above the other and to sprinkle the acting face of the under
Carbon contact with iron filings which are kept in place by a rim around the edge
of the Carbon.
The diaphragm of the instrument is attached at its top and bottom to suitable
cleats or supports upon the Case between which supports and the diaphragm are
interposed Buffers or cushions of elastic material for the purpose of preventing the
diaphragm from being influenced by extraneous vibrations On the front of the

page_text: diaphragm is fixed a point or plate of conducting material say platinum and
opposite is the Carbon point carried by an arm of spring metal which is pressed
towards the diaphragm by an adjusting screw Upon the rear face of the diaphragm
is another contact point designed to operato in connection with a contact point
consisting in this instance of a Cylinder of brass or other metal into the top of
which is screwed or inserted a disc of platinum which latter is the contact point
proper. The Cylinder is carried by an adjusting screw stem which screws through
a metal bracket and is provided with a lock nut. By this means the contact can
be adjusted up and down with great nicéty.
I now proceed to describe the contact which operates in connection with the last
mentioned contact point. It may be described in a general way as consisting of
a Carbon button or disc (the contact point proper) which is supported by a bent
spring-acting carrier stem of metal or other good conducting material attached to
the diaphragm. The said stem at its upper end where it is attached to the
diaphragm is for a portion of its length horizontal; at its lower end where the
button is situated it is for a portion of its length vertical so as to directly overhang
the last named contact point thus allowing the button or disc to make at the
necessary times square contact with the Platinum disc of the said point. The
intermediate portion of the said stem extends diagonally between the vertical and
horizontal portions and is flattened so as to in effect be a spring strip. When the
diaphragm is in vibration the effect will be to move the contact to and across or
above the face of the stationary contact beneath-In order to translate this motion of
the contact into an up and down movement or a movement to and from the stationary
contact controlling device (or as I have herein before termed it a "stirrup") is
employed consisting of a stiff strip of metal or other suitable material which at its
upper end is adjustably attached to the casing and thence extends down so that its
lower end shall bear down upon the slanting spring portion of the moveable contact
carrier. The lower end of the stirrup is forked-so-as-to-straddle-the-said-slanting-
portion and thus guide and prevent lateral movement of the carrier.
Under this arrangement it will be seen that the stirrup when the carrier moves
with the diaphragm will act to depress it or permit it to rise according to the
direction of movement thus causing the moveable contact to have motion to and
from the other contact. The moveable contact may be in one piece with or solidly
attached to its carrier if desired, but it is much preferred to have it loosely
connected therewith, the connection being such that it is virtually suspended from
the carrier with capacity for up and down movement with relation thereto―This
may be effected by the following arrangement. Into the lower end of the carrier
arm or stem is screwed a short shank of Carbon having a head on its lower end-
Upon this shank is loosely mounted the Carbon disc or button which is forined
with a hole for the passage of shank and with a recess on its under side to receive
the head; in order to prevent the disc from rotating on the shank the latter has
a square or other equivalent form in cross section and the hole is of corresponding
shape. In this way the disc is loosely suspended from the carrier, the latter acts
only to lift it, whilst its descent is due to gravity.
The principle of operation of the transmitter is fully set forth in the Specification
of the prior Letters Patent herein before referred to and requires no further
explanation here-It is sufficient to say that when the instrument is used 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; the
vibrations of the diaphragm result in alternately charging the Condenser from the
battery and discharging the condenser to line thus transmitting over the line wire
a series of electrical impulses with the effect of reproducing the voice at tho
receiving Station.
On one side of the diaphragm is a Carbon contact plate and above it are
suspended by a vertically adjustable carrier or support one or more loose carbon
contact buttons-On the other side of the diaphragm is a fixed Carbon contact

page_text: with which co-operates the movable and adjustable carbon Contact mounted on
a spring metal arm.
0
Normally these last named contacts have full contact and the contacts on the
other side have only partial or incomplete contact.
Upon the face of the contact plate hereinbefore mentioned is sprinkled loosely
iron or other good conducting metal in a minutely divided condition the same
being kept on the plate by a rim or circumscribing flange.
Each Carbon button is substantially the same in construction and arrangement
as the loose carbon Contact button herein before first described. The shank of each
button is held to the frame or plate on the lower end of Carrier stem by a scrow
which passes down into it through the plate. For preventing fracture of the
buttons they are provided with close fitting metal caps.
The carrier stem fits and is adapted to slide vertically in a sleeve fixed to a
bridge piece and is held in its adjusted position by a set screw.

page_text: I, JOHN HENRY JOHNSON, of 47 Lincolns Inn Fields in the County of
Middlesex, Gentleman, do hereby declare the nature of this Invention for "IM-
PROVEMENTS IN ELECTRIC TELEPHONE TRANSMITTERS," which Invention has been
communicated to me from abroad by James Aloysius Maloney of Washington,
District of Columbia, in the United States of America, and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
This Invention refers more particularly to a Telephone transmitter of the type
described and illustrated in the Specification of Letters Patent No 1452 of
March 20, 1883; but in some respects it is susceptible of application to transmitters
of other types. The said Invention is directed mainly to an improved construction
and arrangement of the contact points through which the impulses, due to the
vibrations of the diaphragm, are transmitted to line; and in this respect is
characterized principally by the combination with the diaphragm of a contact point,
a spring acting carrier therefor, attached to and moving with the diaphragm, and a
controlling device-termed by the inventor "stirrup"-which bears upon the
spring-carrier, and during the vibratory movements of the latter, operates to direct
its movements to and from the stationary contact-point in connection with which
the carriers contact-point works.
It also has reference to-the-carbon-contacts-of-electric-telephone transmitters_
and other instruments in which microphonic contact is required, the object being to
keep the microphonic contact unimpaired and to prevent the accumulation and
building up between the contacts, of fine carbon dust which results finally in
establishing a closed circuit between the contacts, thus incapacitating the instrument
for efficient work. This object can be attained by interposing between the carbon
contacts, loose iron filings or other metal in a state of minute division-the casiest
way of practically carrying out this improvement being to place the carbon contacts
vertically one above the other, and to sprinkle the acting face of the under carbon
contact with iron filings which are kept in place by a rim around the edge of the
carbon.
In the accompanying drawings figures 1 to 6 both inclusive represent a trans-
mitter embodying the first portion of these improvements Figure 1 is a sido
sectional elevation of the transmitter the side of the box or case being removed.
Figure 2 is a sectional elevation of the back part of the apparatus shewing the working
parts the back of the case being cut away or removed. Figure 3' represents on an
enlarged scale a cross section of the movable rear contact point and the lower part
of the stem of its carrier, together with an elevation of part of the stationary contact
point in connection with which it works Figure 4 is a plan of the movable contact
point Figure 5 is a front sectional elevation drawn to a larger scale, of the
transmitter, representing diagramatically the circuit connections. Figure 6 is an
enlarged sectional elevation of the lower part of the carrier. stem hereinafter
described.
A is the case of the instrument, the front wall A¹ of which is covered by the
hinged door A-the voice opening being formed through both A and A² as
indicated by dott d lines in Figure 1. The door A is provided to allow access to
be had to the front contact point for the purpose of adjusting it or for other purpose.
-B is the diaphragm made of a thin sheet of any suitable material such for example
as wood. It is attached at its top and bottom to suitable cleats or supports a
between which and the diaphragm are interposed buffers or cushions a¹ of vulcanized

page_text: rabber or other suitable elastic material, for the purpose of preventing the diaphragm
from being influenced by extraneous vibrations transmitted through the case A
from the wall or other part to which the case is attached. On the front of the
diaphragm is fixed a point or plate c¹ of conducting material (platinum for example)
and opposite the plate or point c¹, is the carbon point c carried by an arm c³, of
spring metal, which is pressed towards the diaphragm by an adjusting screw o³.
Upon the rear face of the diaphragm is another contact point, designed to operate
in connection with a contact point d-consisting in this instance of a cylinder d' of
brass or other metal, into the top of which is screwed or inserted a disc d' of
platinum which latter is the contact-point proper. The cylinder is carried by an
adjusting screw stem d³, which screws through a metal bracket d' and is provided
with a lock nut d. By this means the contact & can be adjusted up and down
with great nicety.
I now proceed to describo the contact which operates in connection with the
contact point d. It may be described in a general way as consisting of a carbon
button or disc e Figs 3 & 4 (the contact point proper) which is supported by a bent
spring acting carrier stem f, of metal or other good conducting material attached to
the diaphragm B. The said stem at its upper end where it is attached to the
diaphragm is for a portion of its length horizontal; at its lower end where the
button e is situated it is for a portion of its length vertical, so as to directly over-
hang the contact point d, thus allowing the button or disc e to make at the necessary
times square or level contact with the platinum disc d². The intermediate portion f¹
of the said stem extends diagonally between the two end portionsff and is flattened
so as to in effect be a spring strip, for the purpose hereinafter described. Under
the arrangement thus far described it will be seen that when the diaphragm is in
vibration, the effect will be to move the contact e to and across or above the face
of stationary contact d. In order to translate this motion of contact e into an up
and down movement, or a movement to and from the stationary contact d, a
controlling device (or as I have hereinbefore termed it, a stirrup) is used which is
shown at g. This stirrup consists of a stiff strip of metal or other suitable material,
which at its upper end is attached to the upper wooden cross cleat or support a
and thence extends down so that its lower end shall bear down upon the slanting
spring portion f¹ of carrier f. The lower end of the stirrup is forked so as to
straddle the part f¹, and thus guide and prevent lateral movement of the carrier;
and its upper end is held to the part a by a slot and set screw connection f³, whereby
the stirrup can be vertically adjusted with a view to assuring it in proper position.
with respect to tho carrier.
Under this arrangement it will be seen that the stirrup, when the carrier moves
with the diaphragm, will act to depress it or permit it to rise, according to the
direction of movement, thus causing the contact e to have motion to and from the
other contact d. I here remark that this arrangement manifestly is applicable not
only to the transmitter herein shown but also to any other instruments in which
microphonic contact is required. The contact c may be in one piece with or solidly
attached to its carrier if desired, but it is much preferred to have it loosely
connected therewith; the connection being such that it is virtually suspended from
the carrier with capacity for up and down movement with relation thereto.
The preferred arrangement for this purpose is illustrated in the drawing. Into
the lower end of the carrier arm or stem is screwed a short shank h of carbon
having a head h¹ on its lower end. Upon this shank is loosely mounted the carbon
disc or button 6, which is formed with a hole e' for the passage of shank h, and
with a recesse on its under side to receive the head h¹; in order to prevent the
disc from rotating on the shank the latter has a square or other equivalent form
in cross section, and the hole e¹ is of corresponding shape as indicated in Figure 4. .
In this way the disc e is loosely suspended from the carrier; the latter acts only
to lift it, while its descent is due to gravity. This arrangement is productive
of most excellent results, and in Iractice is much to be preferred over a rigidly
connected contact point.

page_text: I have indicated what is deemed to be a good form of stationary contact a to
operate in connection with the movable contact just described, but I do not desire
to be understood as restricting myself to that special form.
The circuit connections, and the adjustments in the transmitter shown in the
drawing, are the same as those illustrated in the Specification of the letters patent
herein before referred to. The battery E (Figure 5) having one pole grounded, is
in circuit with the condenser F, through the wire I, binding post C, wire 3, (leading
from the binding post C to the arm c¹) front contact points c, c¹, wire 3, 4, (the
former extending between c¹ and the upper end of the carrier f, and the latter from
the carrier f to the centre binding post B') post B', and wire 2; and the condenser
discharges to line through the wire 2, post B¹, wire 4, rear contact points ed wire 5,
binding post D and line wire 6.
The normal adjustment of parts is such that the points c, c', have full contact,
while the points d, e, have only partial or incomplete contact.
The principle of operation of the transmitter is fully set forth in the Specification
of the letters patent herein before referred to and requires no further explanation
here. It is sufficient to say that when the instrument is used 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; the
vibrations of the diaphragm result in alternately charging the condenser from the
battery and discharging the condenser to line, thus transmitting over the line wire
a series of electrical impulses with the effect of reproducing the voice at the receiving
station.
The second portion of the improvements is illustrated in Figures 7 to 9 both
inclusive. Figure 7 is a side elevation of the transmitter. Figure 8 is a vertical
section of the same from front to rear the line of section being to one side of the
mouth piece which is not represented in this Fig. This Figure also represents in
a-diagrammatic way the circuit connections. Figure-9-is-a-plan-view-of-the-large-
carbon contact plate which in Figure 8 is fixed to the rear face of the diaphragm,
together with the four loose carbon contact buttons which co-operate with it.
A, is the case of the instrument; A¹ is the mouth piece which opens into the
resonating chamber B, closed at the top by the horizontal diphragin C held in
place by cleats a. On the upper or ear face of the diaphragm is the carbon contact
plate D, and above it are suspended by a vertically adjustable carrier or support F,
one or more loose carbon-contact buttons E (four in number in the example illus-
trated) On the front or under face of the diaphragm is the fixed carbon contact b
with which co-operates the movable and adjustable carbon contact c mounted on a
spring metal arm c¹ which is controlled by an adjusting screw c².
Normally the contacts b and c have full contact, and contacts D and E have only
partial or incomplete contact.
The circuit connections and adjustments shown in Figure 8 are the same as those
described with reference to Figures 1 to 6.
The battery G having one polo grounded is in circuit with the condenser H
through the wire I, binding post z, wire 2, arm c¹, front contacts cb rear contact D,
wire 3 binding post y aud wire 4; The Condenser discharges intermittently to
line through the wire 4 post y wire 3, contacts D, E, carrier F bridge F¹ wire 5.
post and line wire 6.
Upon the face of the horizontal rear contact plate D, for the purpose herein-
before indicated, is sprinkled loosely, iron or other good conducting metal in a
minutely divided condition (as indicated at d in Figures 8 and 9) the same being
kept on the plate by a rim or circumscribing flange e.
Each Carbon button E is substantially the same in construction and arrangement
as the loose carbon contact button described with reference to Figures 1 to 6. The
shank of each button is held to the frame or plate h on the lower end of the
carrier stem F, by a screw i, which passes down into it through the plate 1.
For preventing fracture of the buttons they are provided with close fitting metal
caps f¹.

page_text: ---The carrier stem F fits and is adapted to slide vertically in a sleeve I fixed to the
bridge piece F1 and is held in its adjusted position by a set screw j.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed I declare that what
I claim is
First The combination with the diaphragm, of a spring-acting carrier mounted
on the diaphragm, a contact point mounted or attached to the said carrier, and a
stirrup for controlling the movements of the carrier, substantially as and for the
purposes hereinbefore described with reference to the accompanying drawings.
Second The combination with the diaphragin, the spring-acting carrier, and its
contact point, of a stirrup adjustablo with relation to said carrier, substantially as
and for the purposes hereinbefore. described with reference to the accompanying
drawings.
Third The diaphragm, the bent spring acting carrier and its contact point, in
combination with a stationary contact-point and a stirrup which controls and
directs the movements of the carrier, to and from the stationary contact-point
substantially as herein before described with reference to the accompanying
drawings.
Fourth The combination with the diaphragm and the spring-acting carrier, of
a contact disc or button loosely mounted on or suspended from said carrier, sub-
stantially as and for the purposes herein before described with reference to the
accompanying drawings.
Fifth The combination of the diaphragm, the spring-acting carrier, the contact-
disc or button c suspended from or loosely mounted on said carrier, the stirrup for
controlling the movements of the carrier, and the stationary contact point, sub-
stantially as and for the purposes herein before described with reference to tho
accompanying drawings.
Sixth The combination of the diaphragm, the bent spring-acting carrier, the
contact disc or button suspended from or loosely mounted on the lower end of the
said carrier so as to be capable of independent vertical movement without rotation,
the carrier controlling stirrup, and the stationary contact point, substantially as
and for the purposes hercinbefore described with reference to the accompanying
drawings.
Seventh-Tho combination of the diaphragm, the carrier stem f secured thereto
and provided with a slanting spring portion f¹ intermediate between its upper
horizontal and lower vertical ends, the contact button or disc loosely mounted on
the lower end of said carrier stem, the controlling stirrup adapted to operato
against or in connection with the spring portion f¹, and the stationary contact
point, for joint operation substantially as herein before described with reference to
the accompanying drawings.
Eighth The combination of the two carbon contact points and interposed
loose iron filings or other finely subdivided metal, substantially as and for the
purposes herein before described with reference to the accompanying drawings.
Ninth Tho combination of the diaphragın C; carbon contact plate D, having on
its face loose iron filings or other finely divided inctal; carbon contact button or
buttons E, and adjustable carrier F, substantially as described and illustrated in
Figures 8 and 9 of the accompanying drawings.