Improvements in Apparatus for Electric Telephone Systems.
Year: 1890

page_text: Date of Application, 22nd Aug., 1890
Complete Specification Left, 22nd May, 1891-Accepted, 1st Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Electric Telephone Systems.
I, JOHN GRAHAM, of 46 Belmont Street, Haverstock Hill, in the County of
London, Electrician, do hereby declare the nature of this invention to be as
follows:-
The object of my invention is to obtained increased efficiency, compactness, and
simplicity, in the construction of electric switches in which a movable connecting
piece is used for making connection with any one of a number of other connecting
pieces for the purpose of closing or joining up an electric circuit or circuits.
To accomplish such object I employ a rotatory disc provided with a connecting
piece or contact which when the disc is made to rotate is borne in line with a range
of a number of other connecting pieces said connecting pieces forming the terminals
or being in connection with the terminals of separate telephone circuits or lines
each of such circuits or lines usually being distinguished by indicating numbers or
letters. The said rotatory disc is provided with a knob or handle and a pointer for
the purpose of moving the connecting piece to any desired circuit.
In connection with the above described apparatus I employ a telephone.
transmitter and receiver a suspension switch lever a push call lever and where
required a call bell or vibrator an induction coil and a compensation resistance
coil. When the rotatory disc is in its normal position the index finger points to its
own number and the contact or connecting piece is in connection with its own
circuit. The rotatory disc rests in whatever position it may be placed simply of.
its own inertia, and by placing the telephone receiver upon its rest the connecting.
piece is automatically brought back to the terminal of its own circuit from
that of any other circuit by means of a simple device consisting in the arrangement
of a lever and cord in connection with the telephone suspension lever.
Between the call bell and the terminal of the line circuit I introduce an extra
wire in order that while the telephone is engaged in any one circuit any other
circuit may be able to call attention said wire being disconnected by insulation.
when the pointer is at its own number.
I also introduce a novel shunt or derived circuit between the push call lever
and the telephone receiver in which I insert a compensating resistance when
required. The object of this arrangement is to ascertain whether when the call
lever has been pressed the bell acts in the distant instrument for if the distant bell
acts the current will be alternately diverted proportionately to the resistances of
the two circuits partly through the bell circuit and wholly through the telephone
receiver circuit by the making and breaking of contact of the vibratory armature
of the bell of the distant instrument and will consequently be heard through the
receiver very audibly.
With apparatus such as I have just described the opperator would proceed in the.
following manner :-
Assuming for example that the opperator of No. 1, instrument wished to com-
municate with the opperator of No. 3 instrument he would first turn the handle till.
the index finger pointed to No. 3. He would then push the stud of the call bell, if
the bell rings at the distant station it will cause a rattling sound in the
receiver. The opperator of No. 3 will then press the stud of his call lever and
No. 1 will in turn receive a ring upon his bell. He will then take the receiver
from its lever and place it to his ear and speak into the transmitter and when
conversation is finished he will replace the receiver upon its rest and by so doing
the receiver lever will actuate another lever and cord which will draw the pointer
back to its own number.

page_text: In another arrangement of the aforesaid apparatus in place of the rotatory disc
with handle and pointer I make use of another device for switching from one
circuit to another I in this instance employ a number of push pieces or keys
corresponding in quantity to the number of circuits leading into the instrument
each key is provided with a connecting piece and a spring and enclosing the whole
of the levers of the connecting pieces is a chain or cord or other band this band is
also in connection with the telephone suspension lever and upon finishing conversa-
tion with any particular circuit by simply placing the receiver upon the suspension
lever the key of that circuit through which conversation was being carried on is
forced back to its normal position.
In order that the best result may be obtainable under all conditions I mount the
transmitting telephone in a similar fashion to that of a table mirror so that it is
adjustable to any point of delicacy.
A vænst 92nd 1800
JOHN GRAHAM.
COMPLETE SPECIFICATION.
Improvements in Apparatus for Electric Telephone Systems.
I, JOHN GRAHAM of 46 Belmont Street, Haverstock Hill in the County of
London, Electrician do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The object of my invention is to obtain increased efficiency compactness and
simplicity in the construction of electric switches in which a moveable connecting
piece is used for making connection with any one of a number of other
connecting pieces for the purpose of closing or joining up an electric circuit or
circuits.
To accomplish such object I employ a rotatory disc provided with a connecting
piece or contact which when the disc is made to rotate is borne in line with a range
of a number of other connecting pieces said connecting pieces forming the terminals
or being in connection with the terminals of separate telephone circuits or lines
each of such circuits or lines being usually distinguished by indicating numbers or
letters. The said rotatory disc is provided with a knob or handle and a pointer
for the purpose of moving the connecting piece to any desired circuit.
In connection with the above described apparatus I employ a telephone
transmitter and receiver a suspension switch lever, a push call lever and where
required a call bell or vibrator an induction coil and a compensating resistance coil.
When the rotatory disc is in its normal position the index finger points to its own
number and the contact or connecting piece is in connection with the terminal of its
own circuit. The rotatory disc rests in whatever position it may be placed simply
of its own inertia, and by placing the telephone receiver upon its rest the con-
necting piece is automatically brought back to the terminal of its own circuit from
that of any other circuit by means of a simple device consisting in the arrangement
of a lever and cord in connection with the telephone suspension lever.
Between the call bell and the terminal of the line circuit I introduce an extra
wire and a push call lever in order that while the telephone is engaged in any one
circuit any other circuit may be able to call attention and receive a reply: said
wire being disconnected by insulation or otherwise when the pointer is at its own
number.
I also introduce a novel shunt or derived circuit between the push call lever and
the telephone receiver in which I insert a compensating resistance when required.
The object of this arrangement is to be able to ascertain whether when the call
lever has been pressed the bell acts in the distant instrument; for if the distant
bell acts the current will be alternately diverted proportionately to the resistances
of the two circuits partly through the bell circuit and wholly through the telephone

page_text: receiver circuit by the making and breaking of contact of the vibratory armature of
the bell of the distant instrument and consequently it will be heard through the
receiver very audibly.
With apparatus such as I have just described the operator would proceed in the
following manner :-Assuming for instance that the operator of No. 1 instrument
wishes to communicate with the operator of No. 3 instrument, he would first turn
the handle until the index finger pointed to No. 3 he would then push the stud of
the call lever if the bell rings at the distant station it will cause a rattling sound
in the receiver. The operator of No. 3 having received the call will then press the
stud of the call lever of his instrument and No. 1 will in turn receive a ring upon
his bell, he will then take the receiver from its lever and place it to his car and
speak into the transmitter and when conversation is finished will replace the
receiver upon its rest and by so doing the receiver lever will actuate another lever
and cord which will draw the pointer back to its own number.
In another arrangement of the aforesaid apparatus in place of the rotatory disc
with the handle and pointer I make use of another device for switching from one
circuit to another I in this instance employ a number of push pieces or keys
corresponding in quantity to the number of circuits leading into the instrument
each key is provided with a connecting piece and a spring and encircling the whole
of the levers of the connecting pieces is a chain or cord or other band this band
may be also in connection with the telephone suspension lever and upon finishing
conversation with any particular circuit by placing the receiver upon the suspension
lever the key of that circuit through which conversation was being carried on is
forced back to its own or normal position. I prefer however to have the said band
entirely free from the suspension lever and then any key of any circuit which may be
down can be again raised by the depression of any one of the other keys.
In order that the best results may be obtainable under all conditions I mount the
telephone transmitter in a similar fashion to that of a table mirror so that it is
adiustable to any point of delicacy.
In order that my invention may be more fully understood I will now proceed to
describe the same in reference to the accompanying drawings in which like letters
refer to like parts in Figures 1, 2, 3 and 4 and again in Figures 5, 6 and 7.
Figure 1 is a front view
Figure 2 a back view and
Figure 3 a side view of one form or arrangement of my invention.
To the inner end of a shaft or spindle a which passes through the cover d of the
casing e is mounted a rotatory disc f to which is affixed a contact maker 9 borne at
its further end in a circular line with a range of contact plates h against each of
which it consecutively rubs when the disc is made to rotate by turning the knob
or handle ; which is shown mounted to the shaft a on the front of the cover d.
The said contact plates h form or are in connection with the terminals of the line
wires of the corresponding instruments comprised within the same system of
which said apparatus constitutes a part. Clamped to the shaft a by the knob j is
an index finger or pointer k which when the knob j is turned, travels in unison with
the contact maker and indicates on the index m the number of the instrument
that is switched into circuit by the contact maker a coming in contact with its
terminal plate h. Against the centre of the disc f and secured thereto by a binding
screw n passing into the end of the shaft a is a pulley o which is in combination
with a cord p and an escapement lever y the object of such combination being that
upon finishing conversation through any circuit other than that of the local instru-
ment by the simple act of placing the telephone receiver t upon its supporting
lever u it causes the lever u to descend upon the short end of the escapement lever
pressing it down and thereby drawing the pulley o and the rotatory disc f round

page_text: until its contact maker g is brought in contact with the plate or terminal / of its
own line where it is brought to rest by the slotted edge of the rotatory disc f
coming against the stop pin v which limits the range of its motion, and also by the
roller w which tilts the short end of the escapement lever y up, in opposition to the
exertion of the spiral spring a from under the edge of the supporting lever u and
thus frees the contact maker g for further use.
A is an extra contact spring for connecting the vibratory bell D with the
contact plate h of the local line in order that while the instrument is engaged
any other instrument may call attention and by pressing the stud F of the
Engaged Reply Lever" G receive a reply without interrupting the conversation
that is being carried on, a code of signals having been previously arranged for that
purpose so that the signal may be understood.
66
H is a piece of insulating material for disconnecting the contact spring A from
the terminal of the local line when the contact maker is in its normal
position.
The spiral spring I surrounding the spindle a between the disc f and the
washer Jopposes just sufficient resistance to the movement of the spindle a to hold
the pointer and the contact maker g in whatever position it may be placed without
too much retarding its action.
M is a contact spring for joining up the
resistance coil R and the telephone circuit
or push button T of the said call lever Q is
attention.
shunt circuit N the compensating
with the call lever Q when the stud
depressed for the purpose of calling
ZE is the terminal plate of the zinc pole of the battery V and also the
terminal plate of the earth or general return wire for the whole of the instruments
of the system.
B. C is the terminal plate of the end copper or carbon pole of the battery V
and connected to the bridge W of the call and reply levers Q and G. The whole
of the cells of the battery V are generally employed for ringing up or calling
attention but seldom more than a portion of them is used for speaking so I have
therefore shown the cells of the battery V divided for the speaking circuit the
course of which I will now particularly describe.
When the telephone t is taken from its supporting lever u the lever u is drawn
up by the action of the spiral spring Y until the insulating piece upon the lever u
is forced against the contact spring a¹ which is in turn raised up in contact
with the spring thus completing the speaking circuit between the battery V
the terminal C the adjustable supporting bracket D¹ the transmitter E the
adjustable supporting bracket D" the primary wire P of the induction coil C¹
the contact springs a¹ and 6 and thence to the terminal plate Z E and to the zinc
pole of the battery V.
The contact springs e¹ and e" are for bringing into circuit the vibratory bell D
or the telephone receiver t according to the position of the supporting switch
lever u; if the lever u is in its normal position the bell D is in circuit, the dome
of which is shown in dotted lines underneath the transmitter E on the front of the
cover d. But if the receiver t is off its support and the lever u is drawn up by
the spiral spring Y the telephone receiver t is in circuit through the secondary
wire S of the coil C¹.
I will now give an explanation of how the apparatus which I have just described
and illustrated in Figures 1, 2 and 3 is performed:
:-
Assuming for example that the person at No. 1 instrument-which is the one
illustrated in the accompanying drawing, as the number of every instrument should
be the first on the index-wishes to communicate with the person at No. 10 instru-
ment. He will first turn the knob j till the pointer k points to No. 10 on the
index m, and the contact maker y which travels in unison with the pointer will
then be in contact with the terminal plate of the line of No. 10 instrument, he
will then depress the push piece T of the call lever Q till the latter comes in

page_text: contact with the bridge W at which instant a current will start out at the battery V
to the plate B C thence to the bridge W to the lever Q and will at this point
divide in proportion to the resistances of their respective circuits, between the
shunt circuit N resistance coil R telephone receiver and thence to the battery V
by terminal plate Z E and the line circuit to disc f the contact maker g the
terminal plate and thence by the line to the bell of the distant instrument; when
if the said bell acts the line circuit will be intermittingly closed and broken by the
making and breaking of contact of its armature as it vibrates between its
contact piece and the poles of its electromagnet. Consequently when the line
circuit is thus broken the whole of the current will be diverted through the shunt
circuit and immediately upon its being again in like manner closed the current will
divide as before between the two circuits in proportion to their respective
resistances and the effect will be audibly indicated by a rattling noise in the
receiver t. In the event of the line circuit being broken or disconnected the
current will not of course reach the distant instrument but will all pass through
the shunt circuit and will produce a loud click in the receiver t every time the push
button T is depressed. But should the line wire be short circuited there will be
only a faint click given by the receiver t as the greater portion of the current will be
diverted through the circuit having the least resistance. There are therefore by this
novel arrangement three distinct indications obtainable with regard to the working
condition of the circuit. Granting however that the person at No. 10 instrument
receives the signal he will in turn depress the call button of his instrument and a
reply signal will be received through the bell circuit in No. 1 instrument, the
current passing into the instrument by No. 10 terminal plate h, contact maker
disc f, call lever (2, connecting plate i lever u contact spring e' vibratory bell B
and thence to the return wire of the terminal plate Z E. Each person in order to
converse will then take his receiver t from its supporting lever upon which the
latter will be drawn up against the contact spring ell which will complete the
speaking circuit as follows:-From No. 10 terminal plate to the contact maker g,
to disc, to lever Q to plate i to lever u to contact spring ell to the secondary
wire S of the induction coil C¹ to and through the receiver t thence to the
terminal Z E of the general return wire and on to and through the distant instru-
ment and back through line to No. 10 terminal plate h; this is the stage at which
I have shown my apparatus in the aforesaid accompanying drawings. In the
meantime should any other circuit wish to call the attention of No. 1 whilst No. 1
is engaged speaking with No. 10 they are enabled to do so through the extra
circuit introduced when the contact maker g is removed from the terminal plate of
its own line by the special contact spring A coming in contact with the terminal h
of the line, which connects up the vibratory bell D therewith through the
engaged reply lever G and without interrupting his conversation with No. 10,
No. 1 can return a reply by depressing the push button F of the lever G, a
prearranged code of signals enabling the person so communicated with to under-
stand the meaning of the rings or signals returned. Upon finishing conversation with
the person at No. 10 instrument the person at No. 1 instrument will place his
receiver t upon its support u which will be drawn down against the short end
of the lever g and consequently the contact maker g will thereby be brought
round to the terminal of its own line and in circuit with the instrument of
the person who called his attention whilst conversing with No. 10; such person
having left his switch in circuit with the line terminal of No. 1 instrument for that
purpose.
9
Figure 4 shows the escapement lever 9 constructed on slightly different
principles. Instead of using a roller for tilting up the short end of the lever in
this instance the sleeve S' of the lever g is slotted in the shape of an inverted V
which when the lever is forced round upon the side of the pins p' lifts the
lever up and tilts it from underneath the edge of the lever u as explained in the
preceding description in reference to the Figures 1, 2 and 3.
.......

page_text: Figures 5, 6 and 7 show another arrangement of switching apparatus which
may be substituted in place of the aforesaid rotatory disc contact maker y
and escapement lever q In this arrangement I employ a number of keys.or
pushes corresponding in quantity to the number of circuits required.
Referring to Figures 5 and 6, on the front of the cover d is shown the push
buttons or keys P. P the stems of which pass through the cover d and rest upon
the outer ends of the levers g' shown in Figure 6. The said levers gl are pinned
or pivotted to the side pieces or lugs e¹ of the bed plates m¹. Through the tops of
the said levers g¹ pass pointed screws the points of which bear upon the tops of
the bends or curves of the springs which are screwed to the bed or bearing
plates m¹. d' is an endless chain or other band which passes through the grooves
and under the pulleys and over the ends of the levers g'. ₁ are stop pins
passing into and near the ends of the levers g' to guard against the chain getting
over the ends of the levers are contact springs to which the separate line
wires are connected. Contact spring A' is for connecting the bell to the terminal
of its own line when the instrument is switched to that of any other. In order
that the working of this part of my invention may be clearly understood I will now
explain the position its several parts fulfil in relation to the parts of the aforesaid
apparatus which are fully described in reference to Figures 1, 2 and 3. The bed
or bearing plates m' take the place of the rotatory disc and are connected to the
lever Q. The levers are in permanent connection with the bed plates m'
and therefore take the place of the contact maker g. The line contact spring/
serve the same purpose as the terminal plates and are switched into circuit one at
a time by depressing the pushes P P which force the levers g' back at their outer
ends till their inner ends are in contact with the springs h. The endless chain has
just sufficient slack in it to admit of one key P P and one lever g¹ being down at a
time; therefore by the depression of any one of the keys P P
any other key which
may be down at the time will be forced up and by the pressure of the endless chain
against the lever 7. J" is a connection joining bed plates m¹ together. In the
group of parts shown in different positions in Figure 7 I have shown a means L of
regulating or adjusting the endless chain d' whereby it may be tightened or
loosened as the necessities of the case demand. An examination of Figure 7 will
disclose more clearly the part springs play in holding the levers g' down to one
end or the other by pressing against the sides of the points of the screws j¹ when
the said levers are forced over by the keys P P or the chain d'.
In Figure 7 is also shown a section or portion of a circular frame F which may
be adopted to hold the levers g' in place of the bed plates m', and the springs
substituted instead of the springs i, or, in place of either, the bed plates m¹ or the
frame F, the brackets B' may be substituted. In this latter case levers g' would
move or act upon the pins PII and the said levers g' would be continuously pressed
by the spiral spring Sp against the pins or studs St which move or travel in a
circular groove between two centre or stop holes in the side of the said bracket B₁
which conform to the range of play of the said levers o¹.
The keys and levers and other parts constituting this part of my invention need
not necessarily be arranged in an annular order but may be planted or arranged in
straight or other lines as the circumstances of the case require.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1. In telephonic switching apparatus the combination or arrangement of an
escapement lever, contact-maker, and suspending lever, substantially as described
and shown in reference to Figures 1, 2, 3 and 4.
2. The combination or arrangement of parts forming telephonic switching
apparatus substantially as described and shown in reference to Figures 5,
and 7.

page_text: 3. In telephonic switching apparatus the combination or arrangement of shunt
circuit and compensating resistance coil substantially as set forth in reference to
Figure 2.
4. In combination with telephonic switching apparatus the arrangement of
special call and engaged reply circuits substantially as set forth in reference to
Figure 2.
5. In telephonic systems the combination or arrangement of parts forming
switching apparatus with adjustable brackets for transmitter substantially as and
for the purpose herein set forth in reference to Figures 1, 2, 3 and 4.
Dated this 1st day of May 1901
JOHN GRAHAM.