Improved System of Telephonic Exchange.
Year: 1895

page_text: Date of Application, 19th June, 1895
Complete Specification Left, 19th Feb., 1896--Accepted, 16th May, 1896
Improved System of Telephonic Exchange.
1, SALOMON BERDITSCHEWSKY called APOSTOLOFF, of 139, Warwick Street,
Eccleston Square, London, S. W. Engineer do hereby declare the nature of this
invention to be as follows:-
This invention relates to an improved system of automatic telephone exchange
whereby telephonic communication may be established between any two points of
the system without the intervention of any attendant at the central station.
It has heretofore been proposed to accomplish this result by means of a
multiplicity of similar apparatus at the central station, there being as many such
apparatus as there are subscribers lines in connection with the exchange, each of
the said apparatus corresponding to a different subscriber and each comprising as
many insulated contacts as there are subscribers. These contacts were arranged
upon an insulating switch-board at the points of intersection of co-ordinate lines,
the contacts in all the apparatus corresponding to the same subscriber being
connected electrically together. Each apparatus also comprised the mechanisms
necessary to enable each subscriber to put his line wire in telephonic communication
with that of any other subscriber through the medium of the corresponding
contacts and connections. It follows, therefore, that with such a system if the
number of subscribers in connection with the same exchange were 10,000 the
central station would require to be provided with 10,000 identically similar
apparatus each provided with 10,000 contacts the grouping together of which, as
above mentioned, would involve the employment of 100,000,000 connections, that
is to say the square of the number of subscribers, so that such a system is obviously
impracticable where the number of subscribers is great.
The object of my present invention is to enable this great number of plates,
contacts, and their connections, to be dispensed with. In order to enable my
present invention to be more readily understood, let it be imagined that at the
exchange or central station there is a table divided into squares in the manner of a
draught-board, there being as many such squares as there are subscribers; let it
further be supposed that a system of conductors arranged in co-ordinate lines
corresponding to the vertical and horizontal rows of the draught-board squares,
and furthermore that each square of the board contains the accessories necessary
to effect the telephonic connection between the two conductors whose crossing point.
corresponds to that square.
One of these accessories consists of a polarized relay, herein designated a
distributing relay, to whose poles are connected the two members of the circuit or
line wire of the corresponding subscriber. In each square are fixed three metallie
contacts which may be designated as the normal or receiving contacts. One of these
contacts is the "ringing-up" contact, the second is the "conversation" contact,
whilst the third serves for the establishment of the communication in either case.
All the "ringing-up contacts of all the squares of the board are connected
electrically in groups according to the abscissæ, and these groups are connected
respectively with a row of metallic divisions in each square. These rows of
divisions may be designated "ringing-up" rows.
36
66
29
Opposite to each ringing-up" contact is placed the second contact designated
conversation" contact. The "conversation contacts of all the squares are
"

page_text: "2
connected together in groups corresponding in direction (that of the abscissæ) to
the grouping of the "ringing-up" contacts, and these "conversation contacts are
connected with a second row of metallic divisions designated "conversation" rows,
the said rows being placed parallel to the "ringing-up" rows. The metallic
divisions in both rows ("ringing-up" and "conversation") of the same square
which are connected to groups corresponding to the same abscissa are respectively
opposite each other, so that a solenoidal contact hereafter described may be
transferred quickly from a division of the "ringing-up" row to the corresponding
division of the "conversation" row.
"
The third normal contact designated "line" contact, or "communication"
contact, is connected by means of an automatic interrupting device with one pole
of the distributing relay above mentioned, and consequently with one member of
the circuit or line wire of the subscriber, the other member of this same circuit
being connected directly with the other pole of the distributing relay. All the
poles last mentioned are grouped and connected electrically in the direction of the
ordinates, and these groups are respectively connected with the metallic divisions
of another row placed in the same square and which may be designated "communi-
cation rows. It will thus be seen that in each square there are three rows of
metallic divisions or contacts and that all the divisions of corresponding serial
order in all the rows of same designation in all the squares of the board are
respectively connected together electrically so that by establishing electrical
communication between any one division of the "communication' row and any one
division of the "ringing-up" row of the same square, the circuit corresponding to
this square will be put in communication with the circuit corresponding to the
square which is situated at the point of intersection of the co-ordinate lines to
which the metallic divisions between which communication has thus been established
correspond.
In consequence of the system of grouping above described the number of
metallic divisions or contacts in each row will be only equal to the square root of
the number of subscribers in connection with the exchange.
""
"
"
Movable contacts are adapted to traverse the "ringing-up" and "communication
rows of divisions or contacts of each square, the function of these two movable
contacts being to place any one division of a "ringing-up
" row in electrical
communication with any one division of a "communication row of divisions or
contacts of the same square, the traversing motion of these two movable contacts
being effected independently the one of the other by meaus of a leading screw,
rack, or other mechanical means provided in any case with a quick return movement
and operated by a suitable electro magnetic propelment whose step-by-step motions
correspond to the impulses of the current sent from the transmitter placed in the
telephone of the "ringing-up" subscriber, these impulses being sent or distributed
by the distributing relay according to their direction, that is to say the movable
contact of the "communication
row is actuated when the relay receives a current
of the one direction and the movable contact of the "ringing-up" row is actuated
when the relay receives a current of the other direction. The movable contact
appropriated to the "communication row is a mere rubbing spring, whereas the
contact which is traversed between the "ringing-up" and "conversation rows is
constituted by a magnetized armature supported with freedom to move longitudinally
within the coil of a solenoid which when traversed carries its magnetized armature
successively over the metallic divisions or contacts of the " ringing-up" row.
The rubbing spring contact is in constant electrical connection with one of the
poles of the relay whereas the armature of the solenoid, whenever this solenoid is
in its initial position, is in electrical connection with the normal "
"line contact,
and at same time the solenoid armature is in electrical connection with the "ringing-
up
contact so that the latter is thus in electrical connection with one of the poles
of the distributing relay through the armature of the solenoid, and consequently
with the line; it is thus evident that once the spring contact has quitted the line
contact and commenced to traverse the "communication row of divisions or
"
"
وو
"
"

page_text: contacts the circuit between the solenoid armature and the line will be opened so
that no current (emanating from another subscriber calling, and entering by the
"ringing-up" contact and the solenoid armature) can pass into the line of the
subscriber sought to be "rung up," whilst this same subscriber is himself
manipulating his apparatus.
It will have been apparent that each normal contact is in alignment with, and at
the commencement of, the row of contacts of the same designation and corresponding
to the same square of the board so that the solenoid, as well as the movable spring
contact, will only when in their initial positions be in electrical connection with the
normal contacts corresponding to the rows of divisions traversed by the said
movable contacts, except that the armature of the solenoid is never in electrical
connection with the "conversation" contact unless it is so placed by the special
action of the apparatus of a subscriber "rung up."
It is also to be remarked that when the solenoid traverses the "ringing-up" row
by sliding from one contact or division to the next, a temporary interruption is
produced by the automatic interruptor above referred to, between the armature of
the solenoid and the line wire in order to avoid "ringing-up" the apparatus of the
subscribers corresponding to the metallic divisions with which the solenoid armature
is in transitory contact. By the employment of an independent electro-mechanical
propelment for each of these movable contacts the subscriber is enabled to traverse
and arrest them at any given moment to effect all necessary manipulations of the
apparatus placed at the central station and corresponding to the subscriber to be
rung up ; and also to ring up, and enter into conversation with, the said
subscriber " rung up," and when this conversation is finished to return all the
mechanisms corresponding both to the subscriber calling and to the subscriber
rung up" to their initial positions.
66
"
In order to enable the subscriber calling to verify the traversing motion of the
two movable contacts the "ringing-up" and " communication rows of contacts
are each supplemented by a pair of electrical interruptors arranged in such a
manner that when one or other of the movable contacts is passing from one.
metallic division to the next of the corresponding row, a single impulse of a
verifying current will enter the instrument of the subscriber calling and actuate
one or other of two indicating mechanisms denoting the serial order of the
metallic division on which the said movable contact is situated for the time being,
the impulses of the verification current sent from the central station to the
instrument of the subscriber calling being distributed by a small distributing relay
which, according to the direction of the current impulse, causes the same to
energize one or other of the electro-magnets by which the corresponding indicating
mechanism is actuated. In the subscriber's telephone there is a third electro-
magnet which actuates an indicator bearing the necessary service inscriptions, this
third electro-magnet being energized by the impulses of a current sent from the
central station not by the verifying devices but by means of a movable bridge or
switch specially arranged to control the electrical connection and situated in the
square of the board corresponding to the subscriber. This switch or bridge is
actuated electro-magnetically and serves to block at a given moment the two
electro-mechanical propelment mechanisms of the two movable contacts, in order
to prevent the possibility of the position of these contacts being altered during the
other manipulations; it also serves to close the circuit passing through the solenoid
armature which was cut as above mentioned during its traversing motion; it also
serves to send positive or negative currents through the coil of the solenoid in
order to bring about the motion of the armature of the solenoid within the coil
33
"
either towards the "ringing-up row or towards the "conversation row of
divisions. A special arrangement of the bridge or switch confers only on the
subscriber " rung up" the power of entering into conversation whereby the secrecy
of the conversation is ensured; lastly it serves to enable the whole of the
mechanism to be mechanically disconnected from the propelling devices in order
that it may be quickly returned to its initial position both at the instruments of

page_text: the subscriber calling and the subscriber called, when the conversation is
terminated.
The impulses sent by the subscriber's instrument to the central station are
produced by means of an automatic rotary commutator of special construction,
actuated by a spring barrel and which by pressure on different push-pieces of the
subscriber's instrument is started and stopped and caused to assume different
positions in the direction of its axis so as to vary the relative positions of the
various metallic portions of the commutator relatively to its contact springs so as to
effect the desired commutation of the direction of the current inpulses sent.
In conclusion, it is to be remembered that the draught-board squares, the
co-ordinate lines, and their crossing points, above referred to, are wholly imaginary,
and that it is by means of the system of grouping described that it is possible to
effect communication between one subscriber and any other subscriber in connection
with a telephonic system comprising, for example, n subscribers (each one of whom
has necessarily bis own point of connection) by means of a number of connections
equal only to 2 √n, and that these connections between the members of the
telephonic circuits are effected invisibly by virtue of the different combinations
of coupling up in groups of the conductors either in series or in parallel.
Dated this 19th day of June 1805
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
I SALOMON BERDITSCHEWSKY called APOSTOLOFF of 139 Warwick Street,
Eccleston Square London S.W., Engineer 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 :-
This invention relates to an improved system of automatic telephone exchange
whereby telephonic communication may be established, between any two subscribers
in connection with the system, without the intervention of any attendant at the
central station, and without increasing the number of wires (connecting the
subscribers with the central station) beyond the double wire ordinarily used for a
metallic circuit.
One of the means which has been proposed to accomplish this result comprise as
many similar pairs of switch boards at the central station as there are subscribers
lines in connection with the exchange, each of the said pairs of switch boards
corresponding to a different subscriber and each switch board of each pair
comprising as many insulated contacts as there are subscribers lines to be con-
nected thereto, so that each subscriber was represented (in each of the pairs of
switch boards corresponding to the other subscribers) by a contact specially
appropriated to him. These contacts were proposed to be arranged upon each of
the switch-boards at the points of intersection of co-ordinate lines the contacts
which correspond to the same subscriber in all the switch boards being consequently
connected electrically together by twice as many wires as there are subscribers.
Each apparatus also comprised the mechanisms necessary to enable each subscriber
to put his telephonic line in telephonic communication with that of any other
subscriber through the medium of the corresponding contacts and connections. It
would follow, therefore, with such a system that if the number of subscribers in
connection with the same exchange were 10,000 the central station would require
to be provided with 10,000 identically similar apparatus cach provided with twice
10,000 contacts the grouping together of which, as above mentioned, would involve
the employment of twice 100,000,000 connections between the contacts, that is to
say twice the square of the number of subscribers, so that such a system is.

page_text: obviously impracticable, by reason of its mere bulk and the number of connections.
to be made, where the number of subscribers in connection with the system
approaches in any degree to that of the subscribers to existing telephonic systems
in great cities.
The object of my present invention is to enable this great number of contacts.
and their connections to be so far diminished as to be brought within practicable
limits.
The extent of the diminution will be readily appreciated when it is understood
that instead of employing a number of contacts equal to twice the square of the
whole number of subscribers, I am enabled to attain the same end with a number-
of contacts equal only to three times the square root of the same number of
subscribers, since it will be seen that by the present invention each contact.
represents not merely one subscriber but a whole group of, say, one hundred
subscribers or more. Consequently the number of wires connecting the terminals.
of the groups in the several subscribers' apparatus at the central station is equal
not to the whole number of subscribers but only to three times the square root of
the number of subscribers.
This result is attained by a special system of grouping, at the central station,.
the positive and negative members of the subscribers circuits and consequently the-
apparatus in which they terminate.
Each group comprises a number of elements equal to the square root of the
whole number of subscribers; the groups of the same sign (+ for example) being.
respectively connected each group with its own contact in a row of insulated
contacts whilst the groups of the other sign are respectively connected each to its
own contact in another row of insulated contacts, so that in each subscriber's-
apparatus at the central station there are two rows of insulated contacts each equal
in number to the square root of the number of subscribers, the corresponding
contacts of all of the rows appropriated to the same sign being connected together..
But the system of grouping the positive elements differs from that of grouping the
negative elements in such manner that the coupling together of any one contact of
the positive row with any one contact of the negative row, will complete one
particular circuit and no other, each possible combination between the contacts of
the two rows therefore corresponding to a different subscriber's circuit.
This cardinal point of the invention will be more readily understood by reference
to the accompanying drawings, wherein Figure 1 is a diagram illustrating such a
system of grouping as one example of the many possible combinations of groupings.
which might be adopted to carry the invention into effect, it being supposed for
purposes of explanation that there are sixteen subscribers in connection with the
exchange. The numbers 1, 2, 3, 4, etc. to 16, represent as many cells C as there
are subscribers' circuits entering the central station.
The signs and indicate the terminal points or couples corresponding to the
several subscribers' circuits. The positive elements of these couples are grouped
together in four groups, each group comprising a number equal to the ✓16,.
that is to say four, and the said groups being respectively connected to the
respective metallic contacts a¹, a², a³, a', whilst the negative elements are grouped
also in groups of four which groups are respectively connected to the respective
contacts the positive elements being taken in consecutive order whilst
the negative elements are taken in such other order of progression that the
positive elements of a group correspond respectively to different negative groups-
and conversely.
A is a travelling switch movable along the row A and connected through a key
with one pole of a battery, whilst B₁ is another travelling switch movable along
the row B and connected with the other pole of the battery. Then by placing the
switch A¹ on any one of the positive contacts (a', for example,) and the switch B',.
on any one of the negative contacts (63, for example,) the circuit will be completed
only through the couple corresponding to that combination of contacts (No. 15 in.
the example illustrated) and so on for any other combination of contacts."
:

page_text: If there were 10,000 subscribers' circuits distinguished by consecutive numbers I
to 10,000, they would be divided into groups of 100, then if the positive elements
(numbered consecutively) be grouped together in one hundred groups of 100 each,
and each group be connected to its corresponding contact, then the negative
elements would be grouped together also in one hundred groups of 100 each, but in
such manner that the negative elements of any one of those groups correspond to
as many different groups of positive elements and conversely. In other words if
the positive elements consecutively numbered 1; 2; 3; 4; etc. up to 10 be
grouped together and connected to the first contact of the positive row of contacts,
then the negative elements numbered 1; 101; 201; 301; 401; etc., up to 9901
would be grouped together and connected to the first contact of the negative row
of contacts. Similarly if the positive elements consecutively numbered from 101
to 200 be grouped together and connected to the second contact of the positive
row of contacts, then the negative elements numbered 2; 102; 202; 302; 402; etc.
up to 9902 would be grouped together and connected to the second contact of the
negative row of contacts, and so on for all the other groups of positive and negative
elements.
It is to be observed that in the case of a subscriber's serial number which is
higher than 100 the juxtaposition of the figures denoting the numbers of the
positive and negative elements thus conjugated forms a figure which corresponds
to the serial number of the subscriber. Thus in the diagram, Figure 2, the
conjugation of the contacts 6 and a closes the circuit through No. 1512 or in
telephonic parlance "fifteen twelve."
Reference is now to be had to the other figures of the accompanying drawings,
which illustrate an example of the practical embodiment of my invention, wherein
Figure 3 is an external perspective view (partly broken away) of one of the cells
at the central station, shewing the external wires connecting the corresponding
contacts of different cells. Figures 4x, 4, 42, are each drawn in two parts on
separate sheets the lower parts of the figures being on a larger scale than the
upper parts and representing three of these cells developed or opened out in the
flat to shew the mechanisin and accessories contained therein (each segment of
the cell being partly broken away) whilst the upper parts of the said figures shew
the corresponding transmitters. The three Figures 4* 4 and 42 together constitute
one general diagram illustrating the positions corresponding to the establishment
of communication between subscriber X whose apparatus is shown in Figure 4*,
and subscriber Z whose apparatus is shown in Figure 42, assuming X to be the
subscriber calling and Z the subscriber called, whilst Figure 4, shews the normal
position of the mechanism. Figures 5, 6, 7, shew detail views of the switch
propelment mechanism. Figures 8, 9 and 9 shew details of the bridge switch
hereafter referred to, the looped arrows which point to reference letters indicating
the connections of the various parts from which the arrows lead with the parts of
the mechanism shown in other figures. Figures 10 to 17 shew details of the
numerator-operating mechanism and of the current-commutating mechanisms of
the transmitter for bringing about the operation of the bridge switch of the cell.
Figures 18 to 21 shew details of the indicator-mechanism and of the mechanism
for sending current impulses from the transmitter to the corresponding cell at the
central station for bringing about the operation of the travelling switch propelment
mechanisms. Figures 22 and 23 show details of the contact roller of one of these
switches. The same reference letters and numerals indicate corresponding parts in
all the figures.
In the practical embodiment of the principle set forth diagrammatically in
Figures 1 and 2, each subscriber is represented at the central station by the
"couple" forming the terminals of his circuit (the elements of the various couples
being grouped as above described) and also by a set of apparatus comprising the
two rows of contacts A, B; the travelling switches A¹, Bi; the mechanisms for
moving the latter; a third row of contacts A, parallel with and opposite to row A;
and other accessories which will be described later on.

page_text: All these apparatus may be contained in a pigeon hole or tubular cell C made of
nsulating material and which may, for convenience of mounting the apparatus
therein, be constructed of four segments hinged to a common base so as to open
out flat, as shewn in Figures 4%, 4%, and 42, the segments fitting together tightly
at the joints and the cell being hermetically closed to protect the mechanism from
aust.
The construction and arrangement of the mechanism will, for convenience, be
described in the first place with regard to Figure 4, which shews the parts in
their initial position, (it being understood that the same description applies also to
all the other cells at the central station) whilst the description of the working will
apply more particularly to Figures 4x, and 42.
A is the row of insulated contacts to which are connected the respective groups
of positive elements, and B is the row of insulated contacts to which are connected
the respective groups of negative elements of the several couples formed by the
Beveral subscribers' circuits; A' is the travelling switch movable along the row A;
B' the travelling switch movable along the row B; and A² the third row of
contacts grouped similarly to row A. Each subscriber's line is in constant
communication with the corresponding cell, as shewn.
The means whereby the switches A', B', are caused to move along their
respective rows of contacts A, B, are similar and the description of the mechanism
of one will be sufficient for both, but it is to be understood that the whole of the
mechanical devices hereinafter described are given merely as one example of the
various means which may be employed for producing the requisite movements and
that the invention is in no way limited thereto or dependent thereon.
This mechanism is shewn in detail in Figures 5, 6 and 7, Figure 5 being an inside
face view of as much of one side of the cell as is necessary to show the mechanism
of the switch A', Figure 6 a side view partly in section of the propelment mechanism
of the same switch, and Figure 7 a sectional plan view of the cell looking upwards,
the propelment mechanism of the other switch being omitted.
The travelling switch A¹, is carried by an arm fixed to a nut d which being
prevented from turning (by means of a guide rail 10 fixed to the side of the cell
and straddled by a forked arm carrying two friction rollers d¹) is caused to travel
along a screw spindle D having a fast-pitched screw thread. This screw spindle is
placed parallel to the row of contacts A, is journalled to revolve in bearings, and
receives step-by-step rotary motion by means of a propelment mechanisin consisting
of a ratchet wheel D', fixed on the screw spindle D and engaged by a click d',
carried by a disc D³, loose on spindle D and actuated through a lever e, in the one
direction by the armature of an electro-magnet E and in the other direction by the
antagonistic spring, the pitch of the screw D being such that by each advance of
the ratchet wheel to the extent of one tooth produced by each impulse in the
electro-magnet E, the switch A³, is moved from one metallic contact to the next of
the row A.
In order to provide for a quick return motion of the travelling switch to its
normal position the advance motion of the mechanism is caused to wind up a coiled
The spring D²,
spring D2 which gives the motive power for the return movement.
is contained in a barrel fast with the ratchet wheel D', the one end of the
spring D2, being connected to the barrel and the other end being attached to
a fixed point so that as the screw spindle D is turned to the right the
spring D2, is wound up. A detent ², engaging with the ratchet wheel D',
retains it after each step in advance, so that when the travelling switch A', has
been moved to a certain position it there remains until the quick return
mechanism is allowed to come into action. This is effected by means of an
electro-magnet E², whose armature disengages the click d', and detent &², from the
ratchet wheel D₁, which wheel being free revolves quickly to the left under
the force of the wound-up spring D2. The armature of E, thus acts, through
the agency of a second disc D4, carrying two studs d', d', respectively adapted
to pass under the click d', and detent d³, and so disengage them from the ratchet

page_text: wheel D¹, when the disc D' is pulled to the left by the armature of electro-magnet E³
acting through link e. The disc D, is retained in this position by a lever d³,
engaging with a stud do, on the disc, which lever remains so engaged, until the
return of the switch carrier d to its initial position whereupon the switch carrier
causes the withdrawal of the studs d, and allows the clicks d', d², to again engage
with the ratchet wheel D¹. This is effected by the switch carrier d striking against
a lever d', connected by a link d³, with the lever d³, and so disengaging it from the
stud d, thereby allowing the disc D, to be returned to its initial position by
another spring.
The mechanism for operating the switch B' is similar and is mounted on the
second side of the cell, the only difference being in the constitution and function of
the switches themselves.
The switch A¹ is formed by the magnetized core of a solenoid, placed perpen-
dicular to the row of contacts A and as the latter are arranged vertically in the
cell C the core of the solenoid is horizontal. It is guided within the solenoid coil
within which it is free to slide to and fro when influenced by currents of different
-direction passed through the solenoid coil for the purpose of causing the switch to
be transferred from the contact of row A (to which it has been brought by the
above described propelment mechanism) to the corresponding contact of the row of
contacts A³, fixed to the third side of the cell C opposite that to which the row
of contacts A is fixed.
The switch B' is for the sake of clearness, shown in Figures 4*, 4 and 42, as a
simple spring finger bearing upon the row of insulated contacts B but the acting
end of the finger is in fact a small metal roller b (Figures 22 and 23) capable of
making only a half revolution about its journal, the roller having an insulating
segment 6', in such relation to a stop 62 which limits the rotation of the roller, that
during the advance motion of the switch the roller will turn until its metal portion
slides on the divisions B whilst during its return motion it will turn back and
bear by its insulating segment on the divisions over which it passes.
To the fourth side of the cell are fixed :-(1st) A polarized relay F to whose
terminals F are connected the two members a a¹ of the circuit or line wire of the
subscriber to whom the particular cell under consideration corresponds; the
function of this relay being to distribute to one or other of the electro-
magnets E, E, or E, the currents from a local battery ẞ according to the
direction of the currents received by the relay from the subscriber's transmitter ;
and (2nd) a movable bridge switch G actuated by the electro-magnet E4, and
serving for a number of different purposes hereinafter described.
The relay F is of ordinary construction, its armature f being pivoted at f¹, to the
one pole of a permanent magnet and provided with a tongue switch, which oscillates
between the two contacts f³, f, and serves to thus close the circuit of the local
battery through the coils of one or other of the electro-magnets E, E¹, or E*.
The bridge switch G, which is shewn separately in plan view in Figure 8 and in
section in Figure 9, comprises :-(1st) A number of divisions or contacts 9 in one
with the quadrant-shaped body portion G but separated from one another by
insulating divisions. These divisions are shifted beneath a spring contact finger g¹,
to an extent equal to the distance of one division g to the next, at each current
impulse passing through the electro-magnet E, the finger terminating in a metal
roller g³, (shewn in Figure 94) having an insulating segment and capable of limited
rotation in the same way as the roller of the switch B₁; (2nd) a number of spring
contact-bars i, i¹, 2, 3, which (by the movement imparted to the switch by the
electro-magnet E,) are moved over a number of fixed contacts it, i³, 16, 17, 2³, 1º, 220,
1,2; (3rd) a spring contact bar j, j', which is similarly movable over fixed
contacts, the last mentioned contacts being situated in a different path to
that occupied by the contacts, to 12. This switch G may conveniently be movable
about a pivot and actuated from the armature of the electro-magnet E, through a
click g, and ratchet quadrant; or the switch G might have a rectilineal motion by
a click and ratchet rack.

page_text: In either case the switch G receives a sudden and complete retura
action of a spring g', which is allowed to come into action when the electro
magnet E, energized by a current releases the click ", which happens
simultaneously with the return motion of the travelling switches A, B¹.
The ratchet quadrant is also engaged by a detent g³, which retains it during each
retrograde motion of the click g², the simultaneous release of g², and go, from the
ratchet quadrant being effected by a rod e³, attached to the armature of electro-
magnet E, the head of the rod e, sliding against a fixed inclined cam surface e
and so lifting the click 92, whilst the rod e, which engages by a stud with the tail
of the detent g, draws said detent out of engagement.
Lastly there are three terminals K, L, M, which may be designated the terminals
of the norinal contacts. The terminal L is the "call" terminal, the terminal M is
the "conversation" terminal, whilst the terminal K serves in common for the
completion both of the "call" and "conversation" circuits.
The terminal K is in permanent connection with one terminal of the relay Fand
consequently with one member of the subscriber's line, the other member of the
subscriber's line being in permanent connection, through the other terminal of the
relay, with the terminal L. The terminal K is permanently connected with
the normal contact k¹, on which slides the spring contact k carried by the
switch B', which latter is consequently always in connection with one member of
the subscriber's line.
The terminal I. is connected, through an automatic interrupter, with the normal
contact situated at the commencement of the row A, the interrupter being so
arranged that the connection between Land (Figure 3) is severed in either of the
following events, namely:-when switch B', has moved at all from its initial
position, or when switch A¹, has moved more than the distance of one tooth of its
ratchet wheel D', from its initial position.
The terminal M is permanently connected with the normal contact m which is the
first division of the row A³
All the "call" terminals L of all the cells C at the central station are connected
electrically with their respective normal contacts each through an automatic
interrupter as above mentioned and all the normal contacts are made of a length
equal to two metallic contacts and the intervening insulating division, so that each
normal contact includes in itself the first division of the row A of contacts. The
normal contacts of different cells are not connected together and consequently
the first divisions of the rows A are not connected together. This applies to the
first 100 cells and also to all the others.
All the normal contacts of the second hundred cells are connected each with
the second division of the row A of its cell, as shewn diagrammatically in
Figure 4. All the second divisions of the rows A of the second hundred cells are
connected together by an external grouping wire 2 A whereby the normal contacts
and terminals L of the second hundred cells are connected in a group, this wire 2 A
however also connecting together the second divisions of the rows A of all the
other cells.
Similarly all the normal contacts of the third hundred cells are connected each
with the third division of the row A of its cell, as shewn diagrammatically in
of the third hundred cells are
Figure 4, and all the third divisions of the rows
connected together by an external grouping wire 3 A whereby the normal contacts/
and terminals L of the third hundred cells are connected in a group, the wire 3 A
however also connecting together the third divisions of the rows A of all the
other cells.
Similarly for all the other groups of one hundred each, the number of such
groups being preferably limited (for the rows A) to ninety-nine groups of one
hundred each for a purpose hereafter mentioned.
It will be seen by the drawing that Figure 42 belongs to the twelfth group, its
normal contact being connected with the twelfth division of row A.
These rows of divisions A may be designated "call" divisions.
B

page_text: All the terminals K of the first group of one hundred cells are connected each
with a division of the row B of its cell different to those divisions to which the
other terminals K of that hundred cells are connected in their cells. The
terminal K of the first cell of each hundred cells (that is to say No. 1, No. 101,
No. 201, etc. up to No. 9901,) is connected with the first division of the row B of
its cell and all the first divisions of the rows B of all the first cells of each
hundred cells are connected together to constitute a group by the wire IB
whereby the terminals K of those particular cells are consequently connected in a
group this wire 1 B however connecting together the first divisions not only of the
cells forming that group but the first divisions of the cells of all the other
groups.
The terminal K of the second cell of each hundred cells (No. 2, No. 102, No. 202,
No. 302, etc. up to No. 9902,) is connected with the second division of the row B
of its cell; and all the second divisions of the rows B of all these cells are connected
together by the wire 2 B to form a second group; this wire 2 B connecting together
the second divisions not only of the cells forming that group but also the second
divisions of the cells of all the other groups.
The terminals K of the other cells of each hundred cells are similarly grouped
and connected with the divisions corresponding to those groups.
It will be seen by the drawing that Figure 4* belongs to the group 1B;
Figure 4 belongs to the group 2 B and Figure 42 belongs to the group 15 B.
The "
"
conversation terminals M of all the cells are connected each with its
normal contact m and this normal contact is connected to the contact of the row A',
which is opposite to the contact of row A to which the normal contact b of the
same cell is connected, the grouping of L and M being identical consequently the
terminal M in Figure 4x is connected to the second division of the row A³;
the terminal M in Figure 4 is connected to the third division of the row A²; and
the terminal M in Figure 42 is connected to the twelfth division of row A². The
corresponding metallic divisions of all the rows A2, of all the cells are connected
together by wires such as 2 A2; 3 A², 4 A2, 12 A2. Each row A2, of "conversation "
divisions is placed as above described parallel to the "call" row A, the "call
and "conversation" divisions (which are identically grouped) being respectively
opposite each other so that the solenoid core of the travelling switch A', before
described, may, at the required moment, be transferred quickly from any division
of the "call ' row A (to which it has been moved by its propelment mechanism)
to the corresponding division of the "conversation
row A².
"
It is however to be observed that the terminals M although grouped identically
with the grouping of terminals L, are not normally in connection with either
member of any subscriber's circuit, this connection being only made when the
solenoids of the subscribers entering into conversation, are transferred to their
respective rows A².
The consequence of the system of grouping above described is that the number
of metallic divisions or contacts in each row will be only equal to the square root
of the number of subscribers in connection with the exchange, (assuming that the
two rows have equal numbers of divisions) and this is the cardinal feature of the
invention, the importance of which will be readily appreciated.
It will thus be seen that the function of the travelling switches A', B¹, which
correspond to the two members of a subscriber's circuit is to place the two members
of the circuit of that subscriber (when he desires to call another subscriber) in
electrical communication respectively with any one division of a "call" row and of
"
communication row, and consequently with the two members of the circuit of
the subscriber to be called and to whom this particular combination of "call" and
"communication" divisions corresponds.
a
"
The travelling motion of these two switches is effected independently the one of
the other, by means of the propelment mechanism described, or by any other
mechanical movement, operated by the electromagnet E or E', the step-by-step
motions of the one or other travelling switch corresponding to the impulses of the

page_text: current sent from the transmitter placed in the telephone of the subscriber
"calling"; these impulses acting on the distribating relay F according to their
direction so that the "communication" switch B', is actuated by the local battery B
when the relay F receives a current of the one direction and the switch A¹, is
actuated by the local battery ẞ when the relay F receives a current of the other
direction.
The switch B¹, is as above mentioned in constant electrical connection with one
of the terminals of the relay F, whereas the magnetized core of the solenoid A',
(so long as B', has not moved, and so long as this solenoid is still on its normal
contact) is in electrical connection (by wire t, contacts t³, t, t³, wire t",
contacts to, t, finger 18, and wire t¹, as shewn clearly in Figure 4*) with the "call"
terminal L so that the solenoid core is thus in electrical connection with one of.
the terminals of the distributing relay F and consequently with one member of the
subscriber's line to which the cell C under consideration corresponds.
It is thus evident that once the switch B', (of the subscriber who is about to
"call" another subscriber) has commenced to traverse the "communication" row
of divisions B the circuit between the solenoid core and the line of the subscriber
calling will be opened, so that no current (emanating from another subscriber who
may at that moment desire to call the first mentioned subscriber) can pass into the
line of this subscriber, whilst this same subscriber is himself manipulating his
apparatus.
وو
As to the normal "conversation contact m the core of the solenoid A¹, is never
in electrical connection with this contact m unless it is so placed by the special
action of the telephonic transmitter of the subscriber to whom this cell corresponds
when this subscriber is called.
It is also to be remarked that when the core of the solenoid A', traverses the
"call" row A by sliding from one division to the next, a temporary interruption is
produced between the solenoid core and the line of the subscriber "calling in order
to avoid operating the apparatus in the cells corresponding to the metallic divisions
with which the solenoid core is only in transitory contact.
This temporary
interruption is due to the fact that as the switch B', must be operated before the
solenoid switch A', is set in motion the circuit will have been broken by the
insulated spring contact t³, (mounted on the switch carrier B',) having already left
the contact plates t³, t' Fig. 4.
By the employment of an independent electromechanical propelment for each of
the travelling switches A', B', the subscriber "calling" is enabled to move them
along the rows A, B, as far as necessary and to arrest them at any given moment
in order to effect all necessary commutations of the apparatus in the cell corre-
sponding to the subscriber to be called; and also to ring up, and enter into
conversation with, the subscriber "called "; and when this conversation is finished
to return all the mechanisms in the cells corresponding both to the subscriber
calling" and to the subscriber " called to their initial positions.
66
con-
Referring now to the subscriber's telephonic transmitter, it is sufficient to say
that it consists of an ordinary transmitter as generally used, the construction,
connections, and working, being unchanged so far as the "calling" and "
versation" are concerned. But where the bell-ringing mechanism is actuated by
alternating currents, produced by a magneto-electric generator, as in the system of
telephone in general use in London, these currents must be rectified and converted
into negative currents in any suitable way, as will be readily understood without
explanation.
But to the ordinary transmitter there is added a special transmitting mechanism
for the purpose of enabling a subscriber to call any other subscriber and put
himself in communication with him.
This special transmitting mechanism and the circuit connections of the parts are
illustrated in Figures 4, 42, and will now be described in detail with special
reference to Figures 10 to 17 whereof Figure 10 shews a face view of the special
transmitter with the cover and front plate removed, Figure 11 being a part

page_text: sectional plan, and Figure 12 a part sectional side elevation of same. Figures 13,
14, 15, and 16, shew details, and Figure 17 is a plan of the current commutating
levers.
The special transmitting mechanism comprises two numerator mechanisms R, R',
of suitable construction for the purposes intended, and these numerators may be
actuated electro-mechanically by means of return currents consequent on the
manipulations of the travelling switches A' B' at the central station, in which case
each numerator would be actuated by a separate electro-magnetic propelment
mechanism, such a mode of actuating the numerators affording a means of verifying
the working of the travelling switches A', B¹.
But in view of the precision with which these switches are operated by the
means herein before described such verification is in practice unnecessary and the
numerators may for all practical purposes be operated mechanically as hereafter
described, in which case only one electro-magnet will be required in my special
transmitter and this for the purpose of operating an indicator bearing service
inscriptions.
These numerators record visibly by the figures exhibited at the front of the
instrument, the current impulses sent by the subscriber "calling" to the relay F
for the purpose of closing the circuit of the local battery at the central station
through the electro-maguet of one or other of the propelment mechanisms of the
switches A', B', in the cell C (corresponding to this transmitter) at the central
station, the numerator R counting the step-by-step motions of the switch B¹, and
the numerator R', counting those of the switch A'.
SO
The mechanism by which the current impulses are sent and the numerators
are operated comprises a spring barrel O (or its equivalent) the operation of the
mechanism depending on the finger pressing upon one or other of two buttons N,N',
the button N corresponding to the part of the mechanism whereby the relay
operated that current impulses are sent from the local battery to the propelment
mechanism of the switch B'; and the button N', corresponding to the part of the
mechanism whereby the relay is operated for sending current impulses from the
local battery to the propelment mechanism of the switch A'. These two
mechanisms are similar in construction and it will be sufficient to describe one of
them, the barrel O actuating the one or other of them through the medium of a
pinion o', and a toothed wheel O'.
is left
The wheel O¹, is constantly in gear with the pinions of two clutches p, p, which
are so adjusted by mechanism actuated from the buttons N, N¹, that when the left
band button N is operated the right hand clutch p', is disengaged and vice-versa, at
the same time that (whichever button N or N₁ is operated) the spring barrel
(which is normally prevented from revolving by the discs P, P¹,) is released and
allowed to revolve for actuating the one or other of the circuit-closing and impulse-
registering mechanisms. When then the button N is operated, the clutch
in gear and drives the disc P whose motion is limited to a half revolution for each
simple pressure on the button N but the motion of the disc P may be permitted to
continue for as many revolutions as may be necessary, the means by which this is
accomplished being as follows:-The button N mounted in the front of the
transmitter case bears upon a spindle n which is free to slide longitudinally in its
bearings and is kept in the forward position by a spring n'. The spindien is
provided with a conical cam 2, adapted to act on a lever g fast on a rocking
spindle Q which also carries a detent lever q whose cranked end is adapted to
engage with one or other of two escapement pins p³, pt, of which there are two
diametrically opposite sets fixed on the face of dise P. The pins p³ p¹ are on
different radii and at different radial distances so that the oscillation of the detent
lever by the cone cam n² will move said detent out of the path of pin p³
into the path of pin p', the return motion of the cam permitting the detent to
return into the path of pin p of the other set of pins, whereby one half revolution
of the disc P is permitted. The rock shaft Q is capable of sliding longitudinally
in its bearings so as to move the detent lever q', entirely out of the plane of

page_text: rotation of the escapement pins p³, pª, thus leaving the disc Pat liberty to make-
any number of revolutions. The rearward sliding movement of the rock shaft Q
is effected by turning the outer head n³ of the button N so that a hole in the
back of the outer head engages with a stud n, fixed in a revolving bush n³,
provided with a crank arm whose pin n°, acts, when so turned, against the inclined
cam surface of a quadrant groove n', made in the face of the lever 9. The
groove n', being concentric with spindle n, the pin n³, on entering said groove.
prevents the lever q from oscillating, whilst the pin no, acting on the inclined cam
surface of the groove, forces the rock shaft Q backwards so as to remove the
detent lever q¹ out of the path of the escapement pins p³ p, the lever q¹ being
returned to position by a spring 92, when the head n³ is turned back to its normal
position.
The torsion of this spring 92 acts to give the return angular motion of the detent
lever g', and the compression of the same spring produces the return sliding motion
of the rock shaft Q, as the case may be.
Each clutch pinion with which the wheel O¹, gears is in one with the corre--
sponding half of the clutch and is loose on the spindle P2, the other half of the
clutch being free to slide on, but turning with said spindle and being pressed into
gear with the loose half by a spring plo.
The disengagement of the one clutch and the leaving of the other clutch in gear
is effected through the medium of a rock lever p engaging by slots pⓇ with the
tail ends of the clutch levers 7, each end of the rock lever being formed with an
inclined cam face p8 against which bears a corresponding cam face formed on the
end of a pin p which projects rearwards from the detent lever q' so that, whether
the rock spindle Q be rocked or be moved longitudinally as above described, the
corresponding arm of the rock lever p will be moved backwards and its opposite
end will be moved forwards, the backwardly moving end of lever p³ not affecting
the clutch lever at that end by reason of the play in the slot p whilst the forwardly
moving end of said lever effects the disengagement of the clutch at that end.
A spring 9 on the rock spindle allows forward motion of said spindle, and of pin p³-
when that end of the rock lever is moved forwards and clearance is left between
the other parts of the mechanism necessary to permit of this motion.
2°
Two tappet pins fixed at diametrically opposite points on the disc P act on a
lever arm fixed to a rock spindle 2 which is actuated in the other direction by
a torsion spring ³. Another lever arm on the spindle ³, carries a crank pin * to
which is jointed a pawl which engages with a ratchet wheel which is in one
with a large ratchet wheel the wheel r being engaged by a spring pawl 28 acting
as a jumper and preventing retrograde motion of the wheel which is geared by a
pawl with a ratchet on the units wheel of the series. A notched wheel S at the
opposite end of the numerator R (Figures 18, 19, 20) determines the oscillation
of a levers whose free end acts as a circuit-closing device to close the circuit of
the subscribers battery between two contacts ss2, at the passage of each tooth of
wheel S, which wheel S is fast with the axis of the wheel so that the circuit
of the subscribers battery is closed at s¹² at each change of figure exhibited by
the units wheel of the numerator R during its forward motion. Suitable means-
are provided whereby the numerator wheels are returned to zero without causing
the transmission of current impulses, when the conversation is terminated.
The return of both the numerators to zero is permitted by pressing on a button N*,
whereby longitudinal motion is imparted to a rod R³ carrying cone cams 10 each-
of which is thus made to act on a pin fixed to the pawl and so disengage
the driving ratchet from the units wheel, so that all the wheels of both the
numerators are free to be returned to zero by any suitable means.
The other circuit-closing and impulse-registering mechanism being similar, it
will be sufficient to refer to it in the general description of the working of my
automatic telephone.
It is to be noted that as the numerator R would not require to be operated
if there were any subscriber's number lower than No. 100 it follows that the use,

page_text: as subscribers' serial numbers, of all numbers below 100 is inadmissible in the
apparatus as here described. It is also to be observed that as the normal contact /
and the first division of row A are one and the same, no number which terminates
with 0, 0, or 01 can be used as a subscriber's number in the present example.
That is to say in addition to the figures 1 to 99 being inadmissible as above
stated the numbers 100, 101; 200, 201; 300, 301; 400, 401; and so on are
excluded from use when the apparatus is constructed as in the present example.
The numerator R' of the subscriber calling must therefore of necessity always
be moved from zero a distance not less than the distance of two teeth of its
ratchet in order to attain to the serial number of the subscriber to be called as
hereafter explained.
The indicator dial U is a ring divided into four seginents respectively
Fearing inscriptions indicative of the phases of operation of the mechanisin
and serving to direct the subscriber in the manipulation of the transmitter.
These inscriptions are brought successively into view at an aperture in the
cover, and may be the following or their equivalents :-"Off," which signifies
the position of repose; "Call," which is intended to signify only to the subscriber
called that a call has been given; "Ring" which is a direction to the subscriber
calling that he should "ring up the subscriber to be called; "Are you there";
which is the equivalent of the usual telephone enquiry and indicates that the
subscriber called is ready to proceed with the conversation.
"
The dial operating mechanism is shown in front elevation in Figure 18 and in
horizontal section (in two positions) in Figure 19, Figure 20 being a side view of
the circuit closing lever S operated by the numerators R.
The dial U is carried by a circumferentially grooved ring U' connected by
screws u¹ to a boss U¹ which turns upon a fixed stud u.
Across the groove U³
project four pins u² fixed to a conical cam dise W adapted to slide upon,
and to turn with, the boss U', the pins u² acting as driving teeth for
engagement by a detent u³, and by the click u attached to a lever u³ connected by
a link with the armature of the electro-magnet E³. The screws u³ pass through
longitudinal slots in a tube w fixed to the cam disc W, and sliding on the boss U,
its closed front end being in position to receive pressure from the stem of the
spring press-button N' so that when the latter is pressed inwards, the cone W will
be moved backwards, thus withdrawing the studs u² from their position across the
groove U2, and therefore out of the path of the driving click u and detent u³ lying
in the said groove, leaving the boss and dial U free to be rotated to the left under
the action of a coiled spring Us attached to the boss U' and to a fixed point, and
which is wound up during the four step-by-step motions of the dial to the right; the
motion of the dial in both directions being limited to a complete revolution by an
arm w shewn separately in side view in Figure 21 and pivoted stop w². A spring w³
returns the cam disc W and pins w to their normal position, when the pressure on
the button N¹ ceases. The cone cam W acts upon a lever W whose other end
engages with the rod R2 so that when the cam W is pressed backwards by the
button N, the cone cams 10 carried by rod R' act on the driving ratchets of the
respective numerators R, R' as above mentioned, the return motion of the rod R²,
being effected by a spring.
It has been mentioned that it is preferred that the number of contacts or divisions
in each row A should not exceed 99, even although there are more than 10,000
subscribers on the same telephonic system. By this limitation of the number of
contacts in the rows A. the numerator R' is limited to a units and a tens wheel, so
that the series of figures exhibited by the numerators R R conjointly (when these
have been actuated as above described, so as to place the switches B' A¹ on the
divisions or contacts whose conjugation corresponds to a subscriber whose serial
number is higher than 10,000) shall always correspond to the serial number of
that subscriber.
The number of contacts in the rows B may however exceed 100, and may
theoretically be as many as 999, without requiring more than three wheels for the

page_text: numerator R, it being understood that when the figures of both numerators are
read together as one, the figure exhibited by the units wheel of the numerator R
occupies the "hundreds" place in the conjoined figures.
Where then the number of divisions in rows B, differs from that in the rows A
the number of subscribers thus provided for may not be a square number, but will
equal the product of the number of divisions in row B multiplied by the number
of divisions in row A, and in that case the number of divisions in a row A (which
is the square root of the whole number of subscribers when A and B have equal
numbers of divisions) is equal to the whole number divided by the number of
divisions in row B and vice versa.
Having described generally the construction of the various parts of the mechanism
of this improved automatic telephone apparatus, I will now proceed to describe its
mode of working, assuming for the sake of example, that it is desired to establish
telephonic communication between two subscribers, and this without the possibility
of a third subscriber overhearing the conversation. These three subscribers will
be distinguished by the letters X, Y, Z.
Figure 4, represents the telephonic transmitter in the office of the subscriber X
and likewise the corresponding cell C, at the central station. Figure 4 represents
the same apparatus belonging to the subscriber Y and Figure 42, represents the
apparatus belonging to the subscriber Z. The dot and dash lines indicate the
wires connecting the transmitters with their respective cells C at the central station
and likewise the connections between the mechanisms of the same cell and between
the mechanisms of the one cell and those of the others.
It is to be understood that, although only three sets of apparatus are represented
as an example, the connections would be similar for any number of cells this
number being limited to a number equal to the product of the number of insulated
contacts contained in one of the rows A multiplied by the number of contacts
contained in one of the rows B, the mechanisms of all the cells being actuated from
the same local battery.
Let it be supposed that subscriber X wishes to enter into communication with
subscriber Z whose number, for the sake of example, is 1512. It will be seen by
the diagram Figure 2, that this number corresponds to the conjunction of division 15
of row B, with division 12, of row A, and as the correspondingly numbered
divisions of the rows B, of all the cells are connected together, and the
correspondingly numbered divisions of the rows A of all the cells, are also connected
together, it follows that the number 1512 corresponds to division 15 of the rows B,
and division 12, of the rows A, of all the cells. If now subscriber X by the
manipulation of his special transmitter, causes the travelling switches B₁
and A¹ which are contained in the cell C at the central station corresponding to
subscriber X, to be placed respectively upon division 15, of the row B and division 12
of the row A, those switches will be in electrical communication with the
switches B' A corresponding to the subscriber Z (by the lines 15B and 124)
assuming that the switches B₁ A¹ of that subscriber are in their normal position.
Consequently the switches B₁ A¹ of subscriber X will be in connection with the
distributing relay F of subscriber Z and therefore with the line wire and telephonic
receiver of that subscriber. Then the subscriber X after certain manipulations
of his transmitter which will be hereafter described will be in position to ring up
subscriber Z.
In order that subscriber X shall place his switch B₁ upon division 15, it is
necessary that he should manipulate button N until by the action of the spring
barrel O the numerator mechanism R exhibits the number 15 which denotes that
the circuit closers has closed the circuit at s¹ fifteen times and has consequently
sent fifteen successive current impulses from the subscribers battery to the
distributing relay F in the cell of the subscriber X. As the contact s¹ is connected
to the positive pole of the subscriber's battery, and as the contact s² is connected
through one member of the line circuit with one pole of the distributing relay F

page_text: in the corresponding cell C, the other pole of that relay being connected through
the other member of the line with the negative pole of the battery the current
impulses sent as above described will be positive in direction.
Each positive current impulse sent into the relay causes the armature fto
oscillate so that the tongue switch f2 bears against the contact f and thus closes
the circuit of the local battery 3. The fifteen positive current impulses sent as
above mentioned will therefore close the circuit of the local battery fifteen times
in succession through the coils of the electromagnet E' provided that the switch A¹
of this same cell is in its initial or normal position.
This is effected in the following manner :-The tongue switch f is in permanent
communication with the positive pole of the local battery at the central station,
and the contact f' is in electrical connection with a metal rod T fixed in the same
cell C, in such position that a spring contact t, attached to the carrier of the
switch A will rub upon said rod, throughout the travelling motion of the switch.
Another spring contact t¹ which is the continuation of t bears (when the switch
carrier is in its initial position) upon a small contact which is in electrical
counection with one terminal of the electro-magnet E¹ whose other terminal is
permanently in connection with the negative pole of the local battery at the
-central station.
The electro-magnet E¹ being thus energised fifteen times in succession will
(through the medium of the propelling mechanism before described) move
the switch B' on to the fifteenth metallic division of the row B where it will
.remain.
By similarly operating the button N₁ of the transmitter the numerator R' is
actuated until it exhibits the number 12 whereby the lever s will have closed the
circuit twelve times between the contacts 58. The contact is connected
'with the negative pole of the subscriber's battery and the contact s is connected
(through the same member of the line circuit as that to which s² is connected) with
one pule of the distributing relay F the other pole of which is connected with
the positive pole of the subscriber's battery. The negative impulses thus sent to the
relay F cause its tongue switch f³ to bear against the contact f³ thus closing the
circuit through the electro-magnet E provided that the bridge switch G is in its initial
position. To produce this result the contact f³ is connected directly with one terminal
of the electro-magnet E, the other terminal of which is connected with a contact j
on which (when this bridge switch is in its initial position) bears the spring
-contact j. The contact j is in one with the smaller contact which latter at the
same time bears on the contact this contact j being connected with the negative
pole of the local battery ẞ the positive pole of which as before mentioned is
connected to the tongue switch f2 of the relay F. This electro magnet E being
thus energised twelve times in succession will operate the propelment mechanism
of the switch A¹ and place it on the twelfth division of the row A where it will
remain.
The number of the subscriber to be called being now exhibited by the instrument
of the subscriber calling, it is necessary (in order to prevent the position of the
switch A being altered by the subsequent manipulations of the transmitter) to cut
off the electro-magnet E from all communication with the relay F thus blocking
the electro-magnet E.
It will be evident that once the switches B' A' have been placed in the requisite
positions, the electro-magnets E¹ E are no longer required to act.
It will be remembered that as the switch A' has been moved, the contact t
has quitted the contact t² and consequently the electro magnet E' is already cut
off from the relay; and, as this electro-magnet E' was energized by positive
impulses, all positive impulses now entering the relay F will pass through the
electro-magnet E', one terminal of which is connected directly with the negative
pole of the local battery whilst the other terminal is connected with a metal
rod T. This rod T¹ is placed in the path of the spring contact t' so that, when the

page_text: carrier of the switch A¹ has been moved from its initial position, the circuit will
be closed between T¹ and T, which as before mentioned is connected with the
contact of the relay F, against which contact the tongue switch f' bears when
a positive impulse traverses the relay, which tongue switch as before mentioned is
connected to the positive pole of the local battery. Thus it will be seen that
when switch A is moved from its initial position, each positive impulse sent into
the relay F will cause the bridge switch G to be moved to the extent of one tooth
by the electro-magnet E' (energized by the local battery) thus breaking the
circuit of the electro-magnet E at j and so making it impossible to actuate that
electro-magnet by a negative current. By the same movement of the bridge
switch G the contact j is placed on another contact 3 and the contact upon the
contact thus closing the connection between ³ and which connection will
remain closed during the remainder of the forward movement of the bridge:
switch G.
The positive current, by which the bridge switch G has thus been moved the
distance of one tooth, is sent to the relay F by the subscriber pressing upon a
third button N2 and thereby operating certain switches in the transmitter which
will be hereafter described, it being sufficient to here state that their operation_is
such that, by a single pressure upon the button N2, there will be sent to the relay Fa
succession of three current impulses; first, the positive current above referred to;
secondly, a negative current; and thirdly, a positive current. The first of these
currents cannot pass through the solenoid, because the communication of the
solenoid core of the subscriber's line bas been cut, by the fact that the switch B'
has been moved from its initial position, and has consequently broken the circuit
of the solenoid core, at the contacts t t which are only connected (when the
switch B' is in its initial position) by the spring contact to mounted on the carrier
of that switch. The first of these three currents (which is positive) therefore acts
only on the relay F and causes the electro-magnet E to be energized by the local
battery, and the bridge switch G to be thereby moved the distance of one tooth
thus cutting at j, jjj the connection between the relay F and the electro-
magnet E; and by the same movement restoring the connection of the solenoid
core with the line by the contact of j with and with . The same movement
of the bridge switch has also brought the first division of the series g into con-
nection with the roller contact gl. The divisions g are all in direct communication
with the positive pole of the local battery, whilst the contact 9' is connected with
one terminal of the relay F the other terminal of which is connected with the
negative pole of the local battery; whilst, as before stated, the two members of
the subscriber's line are connected with the two terminals of the relay, and they
are also connected in the subscriber's transmitter with the two terminals of an
electro-magnet E6.
The effect of closing this circuit between 9 and g', is that a positive current is
sent from the central station, through the electro-magnet E the effect of which is
to cause the indicator dial U in the transmitter to rotate to the extent of one
division of the indicator.
The effect of the second current sent from the transmitter to the central station.
(which current is negative) is as follows: It enters the relay F but produces no
effect on the electro-magnet E, whose circuit is cut and consequently the mechanism
of subscriber X remains in the position to which it has been brought.
The two switches B' A' being connected to the terminals of the relay, this
current therefore enters these switches, passes through the contacts 15 and 12 on
which they have respectively been placed and consequently passes through the
wires 15 and 12A which connect these divisions respectively with the corre-
sponding divisions in the cell belonging to the subscriber to whom the
combination (15)-(12) corresponds, according to the diagram Figure 2. This
subscriber in the present example is subscriber Z, whose number it will be
remembered is 1512.
The switches A' B¹ of subscriber Z being in their normal position, that is to say,
C

page_text: being in contact with the normal or line contacts, the current passes through them
and enters the terminals of the relay F, of subscriber Z. The current being a
negative one causes the tongue switch f of Z's relay to bear against the contact f
thus closing the circuit of the local battery through the electro-magnet E of
Z's apparatus, it being supposed that Z's bridge switch G is in its normal position.
The effect of this is to send a single impulse through the electro-magnet E in
consequence of which the wheel D is moved to the extent of one tooth, and the
switch A is moved a corresponding distance. By this movement the switch A¹
does not leave the normal contact 7, and spring t8 does not quit the two contacts to t
which are of equal length to that of contact l, but the spring contact t¹ quits (2
and consequently breaks the circuit of the electro-magnet Ẹ of Z's apparatus.
By this same movement the spring contact t¹ has passed on to the contact rod T
so as to connect the electro magnet E with the contact f* of the relay F.
Although this negative current passes through Z's line it produces no action upon
the electro-magnet E in Z's transmitter, which it will be remembered is only
capable of being actuated by a positive current. The third current sent by
subscriber X (being a positive current) causes the tongue switch f* of X's relay to
hear against the contact f, again closing the circuit of the local battery through
the electro magnet E thereby moving the bridge switch G, to the extent of
another tooth which is the second from its initial position. The effect of this
movement is to again close at g g', the circuit of the electro-magnet E in
✗'s transmitter, and consequently to again send a positive current from the local
battery at the central station, whereby X's indicator is moved to the extent of
another segment (the second) so that it then exhibits a direction to X to "ring-up.'
This same third current (which is positive) besides thus actuating the relay, passes
through the switches B'A' through the divisions of the rows B A on which they
are placed, through wires 15 B and 12 A to the corresponding divisions of the
rows BA in Z's apparatus, through Z's switches B₁ A' to the terminals of
Z's relay F. It therefore causes the tongue switch f of Z's relay to bear against
contact thus closing the circuit of the local battery through the electro-magnet E,
(the switch A being no longer in its initial position) so that the electro magnet
moves the bridge switch G of Z's apparatus the distance of one division. The
effect of this movement on Z's apparatus is exactly the same as that which was
produced by the movement of the bridge switch G in X's apparatus, that is to say,
the circuit of the electro-magnet E, is cut at j and j and a positive current is sent
from the local battery through g g₁ which current entering Z's line wire, joins the
positive current coming from X, energises the electro-magnet E' in Z's transmitter
and moves Z's indicator the extent of one division thereby notifying to Z that he
is "called."
66
"
Subscriber X now proceeds to follow the direction (exhibited by his indicator)
to ring-up" and this he does by sending negative currents, the apparatus of ✗
and Z in the positions to which they have now been brought being able to give
passage to negative currents, without any other action being produced than that of
ringing. These negative currents whether galvanic currents or rectified magneto
electric currents are sent in the ordinary way.
. I will now describe how the three currents positive, negative, and positive, are
sent by the subscriber in the order indicated by pressing the button N³. The stem
of button N acts on two lever commutators 3 which are connected mechanically
but insulated from one another, and which are constantly connected respectively
with the two members of the subscriber's line and are normally held in the position
shewn by a spring. By pressing the button N' these commutators are caused to
pass, first, over a pair of contacts whereof is connected to the positive pole
of the subscriber's battery, and v to the negative pole of the same battery, whereby
a positive current is sent through the subscribers line to the corresponding cell at
the central station as above described. By the continued movement of the
commutators under the pressure of the button N' the commutator ³ is brought
on to contact 6, and v passes on to a third contact v' which, like v is connected to

page_text: the positive pole of the subscribers battery, so that being always connected with
the negative pole, a negative current is now sent through the subscriber's line to the
corresponding cell at the central station. On releasing the button N2 the spring
returns the commutators to their original position, the commutators in passing over
the contacts on their return movement, again sending a positive current
through the line wire to the corresponding cell at the central station.
1
"
The subscriber Z (having been " rung-up' as before described and the "call"
being confirmed by the inscription exhibited on his instrument) operates the
button N2 of his transmitter, and thus sends three currents from his transmitter to
his corresponding cell at the central station, these three currents being likewise
positive, negative, and positive, in the order above mentioned. The first of these
three currents arriving at the relay F, of Z's apparatus causes the tongue switch f³
to bear against the contact f* and thus close the circuit of the local battery through
the electro-magnet E. This electro-magnet thereby moves the bridge switch G
the distance of one tooths that the contact g' is now on the second division g. The
effect of this is to close the circuit of the local battery at g g' and therefore to send
a positive current through the electro-magnet E of Z's transmitter. The electro-
magnet E consequently turns the indicator of that transmitter the distance of one
segment and exhibits a direction to Z to "ring-up." Besides producing this effect
the same positive current from the subscriber's instrument passes through the
switches B'A' of Z's cell, and through the normal contacts on which they are
situated to the terminals K. L. The terminals K, L, are respectively connected,
K with division 15 of row B, and L with division 12 of row A. of Z's cell; and
as the correspondingly numbered divisious of the rows A of all the cells are
connected together, and as those of rows B are likewise connected together, it
follows that the positive current sent by the subscriber Z enters the switches B'A'
of X's apparatus, and passing to the terminals of the relay F, this current enters
X's line, and (by causing the tongue switch of that relay to bear against the
contact ) closes the circuit of the local battery through the electro-magnet E
thereby moving the bridge switch G of X's apparatus, a third time, the distance of
one tooth. The effect of this is to place the contact g¹ upon the third division g
of the bridge switch, and thereby to send a positive current from the local battery
(simultaneously with the positive current which enters the line directly through
the electro-magnet E of X's transmitter, whereby X's indicator is moved the
distance of one division so that it now exhibits an inscription denoting that the
subscriber can now speak.
The effect of this third movement of the bridge switch G of X's apparatus, is to
place the spring contact bars i respectively on the contacts 10 and to place the
spring contact bars upon the contacts. The contact 10 being connected
with the positive pole, and the contact with the negative pole of a few elements
only of the local battery B and the contacts being connected with the winding
of the solenoid switch A', the effect of placing the bridge switch G, in the position
just described is to send a current of a certain direction, through the winding of the
solenoid of X's apparatus, which current by the inductive action that it produces in
the magnetized core of the solenoid, causes the said core to be moved in the
direction of its axis until its other contact point bears upon the corresponding division
(ie. No. 12) of row A² where it remains. The second current sent by subscriber Z
(which is negative) produces no effect whatever; but the third current (which is
positive) produces the same effect upon the apparatus of Z, as that produced on the
apparatus of X by the first positive current, so that the bridge switch G in
Z's apparatus, has now heen turned to the third position; the indicator has been
turned so as to exhibit the third segment; and the core of the solenoid switch A¹
of Z's apparatus has been transferred from the first division of row A to the first
division of row A2, which division is in permanent connection with the terminal M
of Z's apparatus..
It will be remembered that the terminals M of the normal contacts m are grouped

page_text: in exactly the same way as the terminals L of the normal contacts / of rows A, and
therefore the solenoid core of Z's apparatus is now in direct communication with
that of X.
It is also to be noted that the last mentioned positive current has not acted upon
the mechanism in X's cell, because the solenoid core in that cell has been moved
out of contact with the row A so that the circuit was thereby broken.
It is only now that the two subscribers are in position to enter into conversation
with each other, which they now proceed to do.
The telephonic communication thus established will be apparent by diagram
Figure 2 supposing the solenoids to have been transferred to the rows A2 in X's
and Z's apparatus.
When the conversation is completed the subscriber X presses the button N³
whereby he so operates two commutators v vas to bring them into passing contact
with the contacts vl 10 which are connected, the first with the negative pole of the
subscriber's battery and the second with the positive pole of the same battery
whereby a positive current is transmitted.
When the pressure on the button ceases these commutators return, and in
returning produce the same contacts with the same result viz.: the transmission of
a positive current. The first positive current sent by X closes the circuit of his
battery through the relay F of his cell C, thereby causing the tongue switch to
bear against the contact f* thus closing the circuit of the local battery through the
electro magnet E. This electro-magnet consequently turns the bridge switch G
to the extent of another tooth and has for effect to place the fourth contact g in
contact with y¹ and so send a return current to X's transmitter where the circuit
of the local battery being closed through the electro-magnet E the latter moves
the indicator so that it exhibits its fourth segment bearing the indication denoting
repose or that communication is "off."
By the same movement of the bridge switch G the spring contact bars i i¹ are
placed in communication with the contacts 12 (whereof the first is connected
with the negative pole and the second with the positive pole of a portion of the
local battery) and the spring contact bars are also placed upon the
contacts which it will be remembered are in communication with the winding
of the solenoid. In this position of the bridge switch G a current (of opposite
direction to that which was previously sent through the winding of the solenoid)
will pass through the solenoid winding and will cause its magnetized core to make
a return movement within the coil or winding so that the core is again placed on
the row A of divisions. The same first. positive current enters by the
switches A' B' of X's cells and thence through the grouping wires (by which the
divisions whereon those switches are now situated are connected with the normal
contacts of Z's cell) to the switches A' B' of Z's cell. It there produces the
same effects upon the mechanisms of Z's cell and Z's transmitter, as was described
in respect of the apparatus of subscriber X. The second positive current sent
by X (as above described in respect of the first positive current) will cause
the bridge switch G of X's cell to move forward to the extent of another tooth,
but as soon as the spring contact bars 2 connect the two contacts the
circuit of the local battery will be closed through the three electro-
magnets E E³ Es. The electro-magnets E2 E³ will act on the propelment
mechanisms (whereof one is illustrated in Figures 5 and 6) and so cause the clicks
of the propelment mechanisms of A¹ B¹ to be thrown out of gear and enable these
parts to return to their initial position, the electro-magnet E' performing the
same office in respect of the bridge switch G as will be readily understood. For
this purpose is connected with the positive pole of the battery and with one
of the terminals of each electro-magnet E E E whose other terminals are
connected with the negative pole of the local battery.
The same positive currents also enter the mechanism of Z's cell and there
produce absolutely the same effects, so that the whole of the mechanism (with the

page_text: exception of the numerators) has now returned to its normal position and is therefore
in condition to permit of the manipulation being recommenced when it is again
desired to establish communication.
It will be seen that throughout the manipulation of the apparatus belonging to
the two subscribers X and Z the apparatus of the subscriber Y has remained
entirely undisturbed and this remark applies to the apparatus of all the other
subscribers in connection with the telephonic system. It is furthermore to be
observed that since the solenoid switches A' of 'X's and of Z's apparatus, have
quitted their normal contacts whilst conversation was going on between those
subscribers and since the transfer of the solenoid cores from rows A to rows A"
can only be effected by the operation of the mechanism of the subscriber who has
been "called" and will then only put that subscriber in telephonic commmuni-
cation with the subscriber by whom he was called, it follows that it was impossible
for Y or any other subscriber to "ring up" X or Z or to overhear telephonically
the conversation carried on between X and Z.
Instead of the subscriber being required to press a special button N* for the
purpose of acting on the mechanism whereby the number wheels of the two.
numerators in his transmitter are returned to zero, this effect may be produced
by the weight of the telephonic receiver itself when hung on the ordinary switch.
hook.
In conclusion it is to be observed that the terms positive and negative as
applied to the two members of the subscribers circuit and the mechanism in.
connection therewith, are used merely by way of contra distinction and are
interchangeable, or may be replaced by other terms, whereby the members may be
distinguished the one from the other.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed I declare that what I
claim is :-
1. A system of automatic telephone exchange wherein the members of each
pair (constituting a subscriber's circuit entering the central station) terminate in
independently movable switches capable of being electro-mechanically propelled.
along rows of insulated contacts, the positive members of all the pairs (and
consequently the switches in which they terminate and the contacts on which the
switches normally rest,) being connected in a certain order in groups, which
groups are respectively connected to corresponding contacts of all the rows of
contacts appropriated to positive members; the negative members of all the pairs
being connected in a certain order (different to that in which the positive members.
are connected) in groups which are likewise respectively connected to corre-
sponding contacts of all the rows of contacts appropriated to negative members ;.
the difference between the orders of grouping the positive and negative members
being such that any one group of positive members comprises the positive members
of pairs or couples whose negative members are comprised each in a different
group of negative members, and reciprocally, so that a different pair or couple.
corresponds to each of the different combinations formed by conjoining any one-
of the positive set of contacts with any one of the negative set of contacts, the
numbers of the groups in the two sets of groups of which the contacts are the
terminals, (and consequently the numbers of wires in the two sets of wires.
connecting corresponding contacts) being factors whose product equals the
number of possible combinations and consequently the number of subscribers
who may automatically intercommunicate through the central station, as.
specified.
2. In a system of automatic telephone exchange, wherein the positive members.
of all the subscribers lines, the switches in which they terminate, and the contacts
on which said switches normally rest are connected in groups, and likewise the
negative members, their switches, and normal contacts are connected in groups
differently formed, so that any one group of positive members comprises the

page_text: positive members of pairs or couples whose negative members are comprised in as
many different groups of negative members and vice-versa, the groups of positive
and negative members being respectively connected to all the contacts occupying
corresponding positions in all the rows of positive and negative contacts
respectively; and wherein the two members of each pair terminate in electrically
propelled switches independently movable over the rows of positive and negative
contacts respectively; the combination with the one switch and its row of
contacts, of a third row of contacts opposite thereto and grouped similarly to the
grouping of the elements to which those contacts correspond, the switch in question
being electro-magnetically transferrable from the one row of said contacts to the
other or third row so as to provide an alternative circuit of communication which
by such transfer of the switches from the one set of contacts to the other, becomes
for the time being an exclusive circuit for the purpose of maintaining secrecy, as
described.
3. In a system of automatic telephone exchange wherein the two members of
each subscriber's line constituting a pair terminate in electrically propelled
switches independently movable over rows of positive and negative contacts
respectively, and wherein the positive members of all the subscribers' lines, the
switches in which they terminate, and the contacts on which said switches
normally rest are connected in groups, and likewise the negative members, their
switches and normal contacts in groups differently forme 1, (so that any one group
of positive members comprises the positive members of pairs or couples whose
negative members are comprised in as many different groups of negative members
and vice-versa, the groups of positive and negative members being respectively
connected to contacts occupying corresponding positions in all the rows of positive
and negative contacts respectively) the combination, with electro-magnetic
propelment mechanisms for operating the respective switches and with means of
closing the circuit of the local battery through the electro-magnetic propelment
mechanism of the one or other switch (according to the direction of the current
received from the transmitter) of circuit closing mechanisms respectively adapted
to send, the one a succession of impulses of the one direction, and the other a
succession of impulses of the other direction from the transmitter to the relay, and
of numerator mechanisms for recording the number of impulses so sent, substantially
as specified.
4. In an automatic telephone exchange system wherein the two members of each
subscriber's line constituting a pair terminate in electrically propelled switches
independently movable over rows of positive and negative contacts respectively,
and wherein the positive members of all the subscribers lines, the switches in
which they terminate and the contacts on which said switches normally rest are
connected in groups, and likewise the negative members their switches and normal
contacts in groups differently formed, (so that any one group of positive members
comprises the positive members of pairs or couples whose negative members are
comprised in as many different groups of negative members and vice-versa, the
groups of positive and negative members being respectively connected to contacts
occupying corresponding positions in all the rows of positive and negative contacts
respectively) the combination, with electro-magnetic propelment mechanisms for
operating the respective switches and with means of closing the circuit of the
local battery through the electro-magnetic propelment mechanism of the one or
other switch (according to the direction of the current received by it from the
transmitter) of circuit closing mechanisms respectively adapted to send the one a
succession of impulses of the one direction, and the other a succession of impulses
of the other direction from the transmitter to the relay, and of numerator
mechanisms for recording the number of impulses so sent, the movements of the
one switch and consequently the number of contacts in the row over which it
moves being limited to ninety-nine the corresponding numerator therefore having
only a units and a tens wheel of figures, whilst the movements of the other switch
and the contacts over which it moves and the figure wheels of the corresponding

page_text: numerator are unlimited in number so that the figures conjointly exhibited by the
two numerators may always correspond to the serial number of the subscriber
on whose combination of contacts the switches may for the time being be
placed.
5. In an automatic telephone exchange system wherein the members of each
subscriber's line the switches in which they terminate and the contacts on which
said switches normally rest and over which they are traversed are connected in
groups differently formed for the positive and negative members as herein
described, the combination with each switch carrier of a screw spindle mounted to
rotate and of electro-magnetically operated mechanism adapted to impart step-by-
step rotary motion to the screw spindle, the switch-carrier being formed as a nut
adapted to be traversed upon the screw spindle when it is revolved by the electro-
magnetic propelment mechanism for traversing said switch over the corresponding
row of contacts, as specified.
6. In an automatic telephone exchange system wherein the members of each
subscriber's line, the switches in which they terminate, and the contacts on which
said switches normally rest and over which they are traversed, are connected in
groups differently formed for the positive and negative members as herein
described, the combination with each switch carrier of a screw spindle mounted
to rotate and of electromagnetically operated mechanism adapted to impart step-
by-step rotary motion to the screw spindle, the switch carrier being formed as a
nut adapted to be traversed upon the screw spindle when it is revolved, and of
mechanism for quickly returning the switch carrier to its initial position, said
mechanism being operated substantially as described.
Dated this 19th day of February 1896.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.