Improvements in a System of Automatic Telephone Exchange.
Year: 1896

page_text: Improvements in a System of Automatic Telephone Exchange.
I, SALOMON BERDITSCHEWSKY-APOSTOLOFF of 23, Leadenhall Street in the City of
London, Electrical Engineer; do hereby declare the nature of this Invention to be as
follows:-
This Invention relates to improvements in the construction of the apparatus
employed in the system of automatic telephone exchange forming the subject of a
previous application for Letters Patent dated the 15th day of June 1895, No. 11,951;
and it has for its object in particular to lessen the cost of construction and to
facilitate the installation, working, and supervision of the apparatus at the central
station.
According to the present Invention the mechanisms at the central station which
respectively correspond to the different subscriber's circuits, instead of being
contained in separate cells are contained in any convenient number in the same case
wherein they are arranged side by side and instead of rows of contacts over which the
travelling switches appertaining to each mechanism move being separate contacts
for each mechanism connected by wires externally of the cells, the switches move over
and make contact with the connections themselves which are placed within the case
and form rows of contacts common to all the mechanisms contained in that case. By
dispensing with external wires alternating with and crossing each other in space which
render the installation and coupling up of the cells a work of considerable magnitude
and difficulty and involve liability of making cross contacts, and by dispensing with
separate enclosing cells which prevent the working of the various moving parts being
observed for purposes of supervision and adjustment and which are exceedingly
difficult of access and to replace in position, accidental cross contacts cannot occur.
One side of the case is made of glass and is removable to enable the movements of all
the mechanisms contained to be observed and access thereto to be had. The glass
cover serves as the insulating support for the "conversation" set of contacts, and as
these are not brought into use for the electrical manipulation of the various
mechanisms, the glass cover may be temporarily removed when access is required for
testing and regulating purposes.
In carrying the improvements into effect the two travelling switches of each
subscriber's mechanism travel across and make contact with parallel conductive strips
let into or otherwise affixed to the surface of an insulating slab forming the bottom
or back of the case, the two sets of conductive strips (distinguished as the "call" and
"communication" strips respectively) extending the whole length of the slab and
being preferably arranged at opposite sides of a central portion where the bridge
switch is situated, the paths of the two switches being in the same straight line each
across its respective set of "call" or "communication" strips with the bridge switch
between them, and all the mechanisms contained in the same case being similarly
arranged side by side so that the conductive strips or contacts are common to all.
The glass plate forming the cover of the case has that portion of the inner surface

page_text: opposite to the "call" set of strips provided with similar strips to form
"conversation" contacts which may be formed by strips of metal applied in the form
of foil or deposited as a thin coating or film burnt on or otherwise attached to the
glass.
The corresponding strips of different cases would be connected into continuous
series by flexible wires or other means permitting the independent movement of the
cases for inspection of any particular case without severing the connections with the
adjoining cases. With this object the cases may be arranged horizontally or at any
inclination, be superposed in tiers, and fitted to slide drawer-like in supporting
frames, or they may be set up on edge and be movable in a horizontal direction at
right angles to their plane to permit of access to any one of a number of closely
juxtaposed cases, a convenient arrangement being to suspend the cases or sets of two
or more superposed cases by rollers running on overhead rails. Cases so arranged
may be double-faced, that is, both the front and rear faces are available for carrying
the mechanism. When the cases are so arranged that the action of gravity can
come into play to effect the return movement of the switches the use of a spring for
that purpose as described in my said former application may be dispensed with but
where a spring is required I preferably make the propelment screw tubular to
contain a torsional spiral spring which may be of such considerable length as to
permit of making the requisite number of turns without material variation of the
torsional stress and to diminish friction the screw would be journalled in ball
bearings.
The improvements also relate to the transmitter mechanism and consists in
substituting for the numerators composed of sets of number wheels, and for the
power-actuated mechanism by which they are operated, and for the mechanism by
which they are automatically returned to zero, numerators formed of metal tapes
self-winding on spring barrels which are wound off by turning a winding handle and
caused to exhibit their figures consecutively at apertures in the transmitter casing,
the spring barrels being combined with circuit-closing mechanisms operating as
before described and the automatic return to zero being effected by the self-rewinding
of the tapes on their spring barrels when the latter are permitted to come into action
by the release of controlling detents under the pressure of a button.
The improvements also relate to the construction of the commutators in the
transmitter for sending the one a succession of three currents positive, negative and
positive, in the order named, and the other two positive currents in succession for
the purpose of producing the effects described in my previous Specification. These
commutators are formed by pairs of spring contact pieces on opposite sides of an
insulating block carrying the necessary contacts against which the springs are caused
to abut by the pressure of a button.
Dated this uL J
CTI 1900
COMPLETE SPECIFICATION.
Improvements in a System of Automatic Telephone Exchange.
I, SALOMON BERDITSCHEWSKY-APOSTOLOFF of 23 Leadenhall Street, in the City of
London, Electrical 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 improvements in the construction of the apparatus
employed in the system of automatic telephone exchange forming the subject of

page_text: previous Letters Patent dated the 19th day of June 1895, No. 11,951 and it has for
its objects in particular to facilitate the installation, working, and supervision of the
apparatus at the central station.
According to the present Invention the mechanisms at the central station which
respectively correspond to the different subscribers' lines instead of being enclosed
each in a separate cell, are arranged side by side in cases, any convenient number
being contained in the same case, and instead of using rows of contact studs within
the cells grouped by external conductors the conductors are placed within the case
and contact is made with them directly by the travelling switches of all the
mechanisms contained in that case. By dispensing with external conductors as in
the previously described arrangement, the labour and difficulty attending the
installation and coupling up of the cells and any liability of accidentally making
cross contacts are entirely avoided; and by substituting a case constructed as hearafter
described for separate enclosing cells the working of the various moving parts
may be observed and access may be conveniently had thereto for purposes of
supervision and adjustment, the cover of the case being for this purpose made of
glass and serving as the insulating support for the "conversation" set of grouping
conductors. As these conductors are not brought into use for the electrical
manipulation of the various mechanisms the glass cover may be temporarily removed
when access is required to the mechanisms contained in the case for testing and
regulating purposes.
Reference is to be had to the accompanying drawings forming part of this
Specification wherein Figure 1 is a front view representing (in an elementary
manner) the opposite ends of the same or different cases containing subscribers'
mechanisms at the central station four such sets of mechanisms only being
represented and these being contracted in height. by breaking out the middle portion
of each of the switch-operating screws and also the grouped contact strips, the glass
frame being supposed removed and the ends of the frame partly broken out to shew
the contact strips passing through them. Figure 2 is a horizontal section, the
switch-operating mechanisms being omitted and their positions represented only by
the switches and the pitch circles of the switch propelling screws. Figure 3 is a
vertical section which, like Figure 2, shews the case adapted to have switch-operating
mechanisms mounted at each side of the base board although the mechanism is
represented at one side only. Figure 4 is a face view of one end of the case with the
glass cover in position, Figures 3 and 4 also shewing one of the supporting carriages.
Figure 5 is a front elevation of one of the switch-propelling mechanisms, the middle
portion of the frame the propelling screw and of the electrical connections appertaining
to the switch being broken away and the grouped conductors over which the
switch moves being omitted. Figure 6 is a corresponding vertical section, a few of
the grouped conductors being shewn at the upper and lower part. Figure 7 is an
elevation corresponding to the lower part of Figure 6 viewed from the opposite side,
the solenoid switch being supposed to be in its normal position in these three
Figures. Figures 8, 9, 10, are cross sections on lines 8-8, 9-9, 10-10, Figure 5,
respectively, these Figures representing the solenoid switch mechanism as viewed
from beneath. Figure 11 is a face view, Figure 12 a cross section (on line 12-12
Figure 11), and Figure 13 a side elevation of the other switch, the propelling
mechanism which is similar to that of the solenoid switch being omitted, and the
switch being supposed to have been moved from its normal position. Figure 14 is a
face view, Figure 15 is a side elevation, Figure 16 a central section, and Figure 17 a
detail of the bridge switch or rotating commutator by which the proper sequence of
operations of the mechanism to which it appertains is controlled. Figures 18 and 19
are sectional side and face views of a numerator. The same parts are similarly
indicated in all the Figures, and the same letters being as far as possible used to
indicate parts corresponding or equivalent to those in the previous Specification
already cited in order that the latter may be read along with the present one to
facilitate the comprehension of the working of the mechanism as a whole.
Each subscriber on the system is represented at the central station by a set of

page_text: mechanism comprising a pair of electro-magnetically operated switches A', B',
forming, so to speak, the terminals of the two members of the subscriber's line, these
switches being respectively movable over ro s A, B, of conductors with which the
switches make contact and by which the normal contacts of the switches are grouped
as described in the previous Specification, the conductors B being used both for purposes
of mechanical operation and for telephonic conversation, whilst the conductors A are
used only for the former purpose, a third set of grouping conductors A3 being
provided to which the switch A is electrically transferable at the proper moment. for
the purpose of establishing an alternative circuit used exclusively for conversation
purposes, this set of conductors being carried by a glass plate C forming the cover of
the case.
In the present construction of the apparatus the conductors A, B, are parallel
insulated conductive strips let edgewise into grooves in, or built up with alternating
insulating strips upon, a slab C the conductive strips extending the whole length of
the slab and being preferably arranged the set A above, and the set B below, the
middle portion of the face of the slab where the commutators G of the various
subscribers' mechanisms are mounted. The series A, B, of conductive strips with
which the switches A¹, B¹, respectively make contact are. common, to all the
subscribers' mechanisms which are arranged side by side upon the same face of the
slab.
To economize space both faces of the slab C carry similar arrangements of
conductive contact strips A, B, and switch mechanisms, and each side is covered by a
glass plate C carrying conductors A².
The conductors A at the opposite faces of the slab would be connected by cross
connections, as at 1 in Figure 2, which may either be permanent or detachable (as
shewn) and similarly the conductors of different cases would be connected by flexible
connections, as at 2 in Figure 2, so that corresponding conductors A are continuous
throughout and common to all the mechanisms contained in all the cases of the
installation. Similarly for the series of conductors or contact strips B. To facilitate
connecting up the flexible connections 1 and 2 they may terminate in spring plugs
which are inserted in sockets in- the insulating bed so as to make contact with the
respective conductors.
Assuming that there are 10,000 subscribers to be served there would be 100
contact strips in the series A and 100 contact strips in the series B by means of which
the contacts whereon the switches A1, B1, of the 10,000 subscribers' mechanisms at
the central station normally rest will be grouped in the manner described in the
previous Specification, the only differences being those due to the fact that there is
one normal contact strip common to all the mechanisms of the same group, the
normal contact strip at the commencement of series A being equal in width to two
conductors and the intervening insulation and including in itself the first conductor
of the series A. The 10,000 mechanisms being supposed, for purposes of explanation,
to be divided into 100 groups each comprising 100 adjacent mechanisms, the normal
contact strip is common to a group of 100 mechanisms, the strips appertaining
to different groups of mechanisms being respectively connected to different conductors
of the series A as described in the former Specification. Similarly as regards the
grouping of the normal contact' strips m by the conductors A².
Each switch B is in permanent connection with its normal contact strip k¹ which
in this case is not placed at the commencement of the series B but extends parallel
with the path of the switch so that the latter may always maintain connection with
it by spring finger k. These normal contacts A¹ are grouped differently to the normal
contacts, that is to say in every group of 100 mechanisms the contact strip k¹ of
the first mechanism of the group is connected to the first conductor of the series B;
the contact strip of the second mechanism of the group is connected to the second
conductor of the series B; and so on for the normal contact strips k¹ of all the
other mechanisms of the group, so that each conductor A corresponds to a different
group of mechanisms whilst each conductor B corresponds to the different mechanisms
of the same group. As however the system of grouping forms no part of the present

page_text: Invention it will be unnecessary to describe it more fully or to illustrate it in the
drawings. It only remains to explain that A* and m are exactly opposite A and
and are formed of strips of metal foil cemented or otherwise attached to the inner face
of the glass plate C¹.
The plate C is carried by an inner frame adjustably mounted in an outer
frame C³ so as to enable the strips of series A to be brought exactly on a level with the
corresponding strips of series A, the frame being hinged at the top to the case to
admit of its being swung out to give access to the mechanisms contained in the case,
suitable means (not shewn) being provided of supporting it when thus swung
out.
The strips A2 at the two sides of the same case, as likewise those of adjacent
cases, are continuously connected by flexible connections 3, 4, (Figure 2), similar to
those (1, 2,) before described but in order to avoid disturbing the connections when
the glass cover C¹ is opened, these connections 3, 4, are coupled to sets of short, metal
insulated strips A permanently embedded in the end margins of the frame of the
These strips project within the case a short distance so as to present the inner
ends exactly opposite to the strips A upon the glass each to each; contact being
established between the strips A and the corresponding strips A automatically in
closing the case by insulated springs A one end of each spring being in permanent
contact with a strip A2 and the other end being, by the act of closing the case,
brought into contact with the corresponding strip A³. A convenient means of
supporting these 'springs is a notched or grooved rod of insulating material embraced
by the springs which are received in the notches or grooves, and present their two
ends to contact with the strips A2 A3 as described, this rod being fixed to the
glass-carrying inner frame C as shewn.
Each subscriber's mechanism at the central station comprises a propelment
mechanism for the switch A¹ and another for the switch B', these mechanisms being
arranged above one another in corresponding relation to the conductors A B with
which the switches make contact and being alike in all essential respects. Each
propelment mechanism comprises a screw spindle D having a fast pitched screw
thread receiving step-by-step notion, this mechanism and electrical connections for
the moving parts being mounted on a frame 5 removably fixed to the base slab C, so
that each switch, its propelment mechanism and the electrical connections of that
mechanism, can be removed as a whole for testing purposes without interfering with
the working of the other mechanisms in the same case.
It will be sufficient to describe the mechanism of the switch A¹ and then point out
in what respect the mechanistn of the switch B¹ differs.
The switch A is carried by a nut & which being prevented from turning (by means
of a pair of friction rollers di straddling a guide rod ) is caused by the revolution
of the screw spindle D to travel across the series of conductors or contact strips A.
The screw spindle D receives a step-by-step rotary motion by means of a ratchet
wheel D¹ fixed upon its axis and engaged by a spring-pressed click d' carried by one
arm of a three-armed lever D³ loose on spindle D as a fulcrum and actuated in the
one direction through a bell crank lever and link e by the armature of an
electro-magnet E and in the other direction by the antagonistic spring 6 attached to a
second arin of lever D³, 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 A is moved a distance equal to the pitch of the contact
strips A.
In order to provide for a quick return motion of the switch to its normal position
the rotation of the screw spindle D, due to the advance motion of the mechanism,
winds up a spirally coiled spring Da contained in the tubular screw spindle D and
acting by torsion, the one end of the spring being attached to the footstepped lower
end of the spindle D and the other to the fixed stud 7 (Figure 6) upon which the
upper end of the tubular spindle D is journalled through the agency of a ball bearing,
as shewn, the stud 7 being capable of rotary adjustment and provided with ratchet
mechanism (Figure 8) for the purpose of giving the required initial tension to the

page_text: spring D². By the employment of a screw spindle of relatively large diameter the
obliquity of a fast pitched screw thread is much more favourable for producing
the traversing motion of the nut upon it than with a screw of smaller diameter and
of the same pitch, at the same time that the friction between the screw and nut is
diminished and there is less liability of slackness between them and greater
certainty of moving the nut the exact distance required to place the switch upon a
given contact strip. By making the screw spindle tubular, weight is diminished and
by housing the spring within the screw the space which would be occupied by a
separate spring barrel is saved. Moreover by using a spring coiled in a spiral form
one or more times upon itself in the manner of a roller blind spring, a spring of great
length may be used which may be initially wound to the required tension and of which
the tension will not be materially altered by the few extra turns of the screw required to
traverse the nut from one end of the screw to the other, so that the force of the
spring. tending to produce the return motion and opposed to the propelling
mechanism remains practically constant at all points in the traverse of the
nut.
This
A spring-pressed detent engaging with the ratchet wheel D¹ prevents
retrograde motion and sustains the switch A¹ at any position to which it may have
been raised, until the quick return mechanism is allowed to come into action.
is effected by means ofan electro magnet E² whose armature disengages the click d¹
and detent d from the ratchet wheel D which being thus set free is revolved.
quickly under the force of the wound up spring D2. The armature of E2 acts thus
through the agency of lever 8, link 9, and lever 10, the latter being fulerumed loosely
upon spindle D and bearing with its bevelled end against a pin 11 on the click d¹
which when thereby raised raises with it the detent d². The lever 10 after having
thus moved click and detent d² out of engagement with the ratchet wheel D¹ is
retained (by the hooked end of a spring-pressed lever d engaging with it, as shewn
in Figure 6) until the return of the switch carrying nut d to its initial position,
whereupon nut d strikes against a rod de coupled to lever ds and so disengages the
hooked end of the latter from the lever 10 which is thus permitted to be returned to
its normal position under the action of a spring 12.
In order to neutralize the effect of possible inequalities in the power of the electro-
magnet E, due to variations in the strength of the current energizing it, the
magnet E does not drive direct but puts the spring.6 in tension which by its recoil
gives the propelling impulse to the lever D. To further guard against over-driving
the wheel D is provided with pins 13 corresponding in pitch to the ratchet teeth,
one of which at the conclusion of each forward step of the wheel D¹ is engaged by a
detent 14 mounted on a radius arm 15 pivoted to a fixed point 16 and coupled by a
link 17 with the third arm of the lever D³ so that at each oscillation of said lever
under the action of the electro-magnet E the detent 14 is moved out of the path of the
pin 13 with which it was last engaged and is returned into the path of the next
succeeding pin at each oscillation of the lever under the action of the spring 6.
In order that the detent 14 shall not oppose the revolution of the wheel D¹ during
the return motion the detent is so pivoted to the arm 15 as to form a rigid stop to
motion of the pins only in the one direction, and give passage to the pins in the other
direction a spring 18 tending to maintain it in operative position.
In order to prevent lost motion between the ratchet wheel D' and its driving pawl
the former is made circularly adjustable upon its carrying hub 19 by screws and
slots 20.
To ensure an accurate fit of the nut d upon the screw spindle D the nut is split at
one side and clamping screws 21 are provided for tightening it up.
The nut carrying the switch B and the mechanism for operating it are similar in
every respect, the switch itself and the electrical connections only being different as
hereafter described.
The switch A¹ is formed by the magnetized core of a solenoid 23 clamped in a
bracket 24 mounted on the nut d by means of adjusting screws 25 so that the switch A¹
is presented perpendicularly to the rows of contact strips A and A² and its position

page_text: relatively to the nut and its propelling mechanism may be accurately adjusted so that
at each step-by-step motion of the latter, the switch will coincide in position with a
contact strip. The switch occupies a horizontal position and is free to be moved
longitudinally under the influence of a current of the one or other direction passing
through the solenoid coil which also forms a guide for the switch, the latter being
norinally maintained by a light spring 26, when no current is passing, in contact with
the planed face formed by the exposed edges of the strips A and the insulating
material in which they are embedded, the switch being of such length that its other
end is just clear of the face of the glass plate carrying the series of contact strips A*
so that by the sliding motion of the switch in the direction of its own length it may
be transferred from the series A to the series A or vice versa.
The switch B' differs only in so far that it has no solenoid coil and is formed by a
conductive pin mounted in insulated guides in its bracket 24 and is constantly pressed
by a spring 27 towards the planed face formed by the exposed edges of the
strips B and the insulating material in which they are embedded. "The switch B makes
contact with this surface only during its upward or advancing motion being raised out
of contact on the return motion by the engagement with a stud 28 projecting from it
of an arm 29 fast on the axis of a segment roller 30 mounted in a spring pressed
bearing 31 carried by the bracket 24 so as to bear on a path formed by one side bar
of the fraine 5 the rotary motion of the segment being limited in the one direction
by the stud 28 abutting against the guide of the pin B and in the other direction by
a pin 32 so that at the commencement of the advancing motion of the switch the
ari 29 is withdrawn from the stud 28 by the partial rolling of the segment 30 upon
the frame 5 thereby allowing the switch B' to be moved by spring 27 from its norinal
position (indicated in dotted lines in Figure 13) so that it will make contact with the
first and succeeding strips of series B as it moves over them. During the remainder
of the advancing motion of the switch the segment slides upon the frame 5, the parts
remaining in the same relative position. As soon as the return motion of the switch
commences the segment rolls in the opposite direction and the arm 29 at once raises
the switch B' so that it does not make contact with the strips B over which is passes
during its return motion, the segment 30 again sliding on the frame 5 until the
switch reaches its normal position.
Each frame 5 upon which a switch propelment mechanism is mounted is removably
attached to, and in close contact with, the face of the base board, say, by its lower
bevelled edge being supported upon the correspondingly underent edge of a rail 33
screwed to the base board and by its upper end being secured by a turn-button 34,
the frames 5 being alternated with vertical bars 35 permanently secured to the base
board and serving the double purpose of cross braces to retain the series A, B, of
contact strips and their insulation in position upon the base board and also to support
the conductors by which electrical connection is established with the various parts of
the mechanisms mounted upon the removable frames 5.
In order to enable the frame 5 and the mechanism carried by it to be easily placed
in position between the cross braces 35 each of the latter is shewn as having a gap cut
partly across it and across the electrical conductors fixed upon it which is filled by a
hinged block 22 secured by a button and carrying spring bridges which press upon
the flattened ends of the interrupted conductors and maintain their continuity."
Electrical connection with the switch A¹ is established (subject to the action of the
controlling mechanism) throughout the travelling motion of the switch as follows:-
The switch A is connected by flexible wires (which do not impede the slight
longitudinal motion of the switch above described) with spring fingers 36 and 37
mounted on an insulating bleck on the nut d and in permanent sliding contact with
conducting strips 38, 39, carried by an insulating bed mounted on frame 5, the
strips 38, 39, being connected with spring fingers 40, 41, which bear upon contact
studs 42, 43, in connection with conductors 44, 45, mounted on the adjacent cross
brace 35. The coil of the solenoid is similarly connected with spring fingers 46, 47,
in sliding contact with conducting strips 48, 49, on fraine 5 and connected with
spring. fingers 50, 51, bearing on studs 52, 53, in connection with conductors 54, 55

page_text: The nut d upon which switch A is mounted also carries spring fingers { t¹ insulated
from the nut but in electrical connection with each other which are in sliding contact
the one t with a conducting strip T and the other t' at first (when the switch is in its
normal position) with a short contact and after the completion of its first step with
a conducting strip T. Tand T¹ are carried by an insulating bed fixed to frame 5
and the strip T is connected with a spring finger 56 which bears against a stud 57 in
connection with conductor 58; whilst contact t2 is connected with a spring finger 59
bearing on a stud 60 in connection with conductor 61; and strip T is connected with
spring finger 62 bearing on stud 63 in connection with conductor 64, the
conductors 58, 61, and 64 being carried upon the adjacent cross brace 35. The two
contacts to which (when the switch A¹ is in its initial position) are coupled by the
insulated forked spring & carried by the nut d are connected with spring fingers 65, 66,
which bear upon studs 67, 68, respectively connected with conductors 69, 70.
The coils of the electro-maguet E are connected with spring fingers 71, 72, bearing
on studs 73, 74, connected to conductors 75 and 76. Similarly the coils of electro-
magnet E are connected with spring fingers 77, 78 bearing on studs 79, 80, in
connection with conductors 81, 82. By the use of spring fingers on the frame 5 and
studs on the standing part of the base board, all the electrical connections with the
mechanism carried by the frame 5 are established automatically by the mere act of
placing the frame 5 in position.
The switch 1 is electrically connected by its insulated spring 27 with spring finger k
which is in sliding contact with the normal contact strip carried by an insulating
bed on the frame 5 and in connection with a spring finger 83 bearing on a stud 84
connected with conductor 85. The two contacts t³ which (when the switch B' is in
its initial position) are coupled by the insulated forked spring to carried by the nut d
of said switch are connected with spring fingers 86, 87, which bear upon studs 88, 89,
connected with the conductors 70 and 44 before referred to as connected with the
interrupter contact and the switch A respectively. The electro-magnet. E is
connected like electro-magnet. E by spring fingers and studs with the conductors 90, 91,
and the electro-magnet E is connected (like electro-magnet E) by spring fingers and
studs with conductors 92, 93.
The commutator G (Figures 14 to 17) by which the distribution of the central
station battery current to the electro-magnets E, E, E, E, E, E, is controlled is
identically similar in construction and operation to that described and illustrated in
the Specification of the previous Patent except that the electro-magnets E E' are
placed somewhat differently and act through a somewhat different arrangement of
levers and links as shewn.
The commutator or bridge switch G comprises: (1st). A number of contacts g in
one with the quadrant-shaped body portion G but separated from one another by
insulating divisions, which are shifted beneath a spring finger g' to the extent of one
division at each current impulse passing through the electro-magnet E, the finger
terminating in a metal roller g having an insulating segment and capable of limited.
rotation so as to make contact only during the forward movement of the commutator.
A spring finger g makes contact with the body portion G of the commutator;
(2nd). Insulated bridge contact-bars i, i¹, 12, 13, which are moved over
contracts,, 8ª, 67, 4º, 3º, 2º,, ;(3rd). An insulated bridge contact barj which
is moved over contact j,j, j, j. The commutator is moveable about a central pivot
and is actuated from the armature of the electro-magnet E through a click g² and
ratchet quadranty. It receives a sudden and complete return motion by the action
of a spring when the electro-magnet E, energized by a current, releases the
click g², which happens simultaneously with the return motion of the travelling
switches A, B. The ratchet quadrant is also engaged by a detent g', the simultaneous
disengagement of and g being effected by a rod e coupled to the armature of
electro-magnet the head of the rod e' sliding against an inclined surface eti
and abutting against the click g and also engaging by a stud with the tail of the
detent go.
To enable the commutator to be readily removed for testing it is fixed to the base

page_text: board C in the same way as the frames 5 of the switch mechanisms, and connection
between its various contacts and the standing conductors is automatically established
by the act of fixing the commutator in position by means of spring fingers and
contact studs 94, 95; 96, 97; 98, 99; 100, 101; 102, 103; 104, 105; 106, 107;
108, 109; 110, 111; 112, 113; 114, 115; 116, 117; the spring fingers being respectively
connected as shewn with the various contacts of the commutator and the studs being
respectively connected with conductors which for purposes of identification are
distinguished in the different. Figures of the drawings by the same reference numerals,
so that the electrical connections of the various parts may be easily followed.
The connections of the central station battery and of the subscribers' lines, with the
mechanisms contained in the frane is by wires which externally of. the frame C are
flexible to permit of the frame being moved as hereafter described, +Band - B
being respectively connected with the positive and negative poles of the central
station battery and +8 with the middle part of the same battery and being carried
within the frane for connection with the different parts of the several mechanisms,
as shown by the broken lines in Figure 1. a and a¹ are the two members of the
various subscribers' lines connected with their transmitters (not shewn) and with the
terminals of the polarized relays F of their corresponding mechanisms which are
preferably placed at the upper part of the case C.
Each relay F has an armature f pivoted at f¹ to one pole of a permanent magnet and
provided with a tongue switch which oscillates between the two contacts f f and
serves to thus close the circuit of the central station battery through the coils of one
or other of the electro-magnets E, E³, or E*.
The function of each relay F is identical with, and the electrical connections
established by it under the control of the commutator G between the central station
battery and the various electro-magnets are precisely similar to, the function and
connections described in the former Specification.
Each case C containing a number of mechanisms as above described is suspended
clear of the floor by end carriages 118 having rollers 119 running upon rails carried
by. pairs of girders 120, any convenient number of cases being similarly suspended
upon the same pair of girders upon which they are movable so as to admit of the
eases being normally closely juxtaposed so as to occupy the minimum of space or of
being separated as may be required for access to any one of them for inspection or
adjustment of the mechanism the flexible connections already referred to as connecting
the corresponding conductors or contact strips of the several series A, A, and B being
sufficiently extensible to permit of this separation of the cases without breaking the
continuity of the connection. The travelling motion of the case upon the rails may
be conveniently imparted by a handing rope or chain 121 upon a wheel 122 fast upon
a shaft 123 extending the whole length of the ease and having a pinion 124 at each
end in gear with spur wheels on the rollers 119. The attachinent of the roller
carriages to the frame of the case may be by means of a metal strap extending around
the sides and bottom of the case and the cases may be provided with rubber buffer
stops 125.
In Figure 1 the mechanism indicated by the letter X is supposed to have been
moved by the operation of the transmitter of the subscriber calling, into position to
establish telephonic connection with the telephone of the subscriber called whose.
corresponding mechanism is indicated by the letter Z
The grouping combination of mechanism Z being supposed for example to correspond
to the fifteenth conductor of series B and the twelfth conductor of series A, the.
switch B¹ of the mechanism X has accordingly been raised so as to make contact
with the fifteenth conductor of the series B and the switch A has been raised to the
twelfth conductor of the series A and may be supposed to have been transferred thence
to the corresponding conductor of the series A. The grouping combinations of
mechanism X and of the other mechanisms shewn, being immaterial, they are not
indicated,
Although these mechanisms are shewn in the same Figure they would be contained
in different cases if they appertain to different groups of mechanisms,

page_text: The improvements in the transmitter are illustrated in Figures 18 and 19 which
represent side and face views of one of the two numerator and circuit closing
mechanisms, the other mechanism being identical except that the numbers on the
tape have only two places of figures.
The improvement consists in substituting for the sets of number wheels previously
used, and for the mechanism by which they are returned to zero, numerators formed
of metal tapes which are wound off from one spring barrel to another and caused to
exhibit their figures consecutively at apertures in the transmitter casing, the winding
mechanism being combined with circuit closers operating as before described and the
automatic return to zero being effected by the self rewinding of the tapes on their
spring barrels. The figures represent the left hand numerator which corresponds to
the hundreds, thousands, and tens of thousands places of figures. R is the metal tape
normally wound on a spring barrel 126 and passing over a driving druin 127 having
teeth 128 engaging in holes 129 in the tape, the tape being secured to a second
spring barrel 130, the tension of whose spring is opposed to, but is less powerful than,
that of the barrel 126. In passing over the driving drum 127 the tape is exhibited
at an aperture in the casing the driving and releasing motions being as follows:-
Fast on the spindle 131 of the winding handle 132 is a pinion 133 in gear with a spur
wheel 134 loose on the axis of the driving drum 127 and in gear by a pawl 135 with
a rachet wheel 136 fast with the driving drum, so that by turning the handle 132
the driving drum draws the tape R from the spring barrel 126 until the required
number is exhibited, the tape being taken up by the spring barrel 130, where it is
retained by the pawl 137 engaging with a ratchet wheel 138 fast on the axis of the
winding handle. For every time the figure exhibited at the aperture is changed, a
circuit closer comes into action to close the circuit of the subscribers' transmitter
battery through the subscribers' line as described in the previous Specification, the
circuit closer being formed of a pair of contact springs as which are momentarily
united by contacts s on a wheel S of insulating material in one with spur wheel 134.
The mechanism by which the tape is at the required moment re-wound on barrel 126
consists of pins 139 adapted to come beneath pawl 135 there being as many pins 139
as there are teeth on ratchet wheel 136 (the number of said teeth corresponding to the
number of tape figures exhibited during a single revolution of the drum) these pins
being carried by arms 140 fast on a rock shaft 141 which also forms the axis on which
drum 127 and wheel 134 run loose and which is common to both of the numerator
mechanisms of the transmitter. The rock shaft 141 has an arm 142 to which is
connected a link 143 actuated by the push button which effects the release of the
indicator dial (not shewn) as described in the previous Specification, so that by rocking
the shaft 141 the pawl 135 of each numerator mechanism is lifted out of engagement
with its wheel 136 by the adjacent pin 139 thereby allowing the spring barrels 126 to
rewind the tapes without revolving spur wheel 134 and consequently without causing
the circuit closer to come into operating during the rewinding.
In order that the pins 139 shall not obstruct the rotation of the pawl 135 with
wheel 134 during the drawing off of the tape, the pawl 135 is formed with a bevelled
face and the pins 139 are mounted to slide in guide holes in the arms 140 and are
pressed into operative position by springs 144 so that on the bevelled face of the
-pawl 135 meeting a pin the latter recedes and allows the pawl to slip past it.
In other respects the transmitter is substantially identical in construction and
operation with that described in the previous Patent and it is unnecessary to again
describe it or to repeat the general description of the apparatus as a whole."
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that what I
claim is :-
1. In the herein described system of automatic telephone exchange, mounting a
number of the mechanisms side by side in the same case so that the switches work
over and make contact directly with series of grouping conductors extending within

page_text: the case and accessible in common to the switches of all the mechanisms substantially
as specified.
2. In the herein described system of automatic telephone exchange, mounting a
number of the mechanisms side by side in the same case so that the switches work
over and make contact. directly with series of grouping conductors extending within
the case and accessible in common to the switches of all the mechanisms and providing
the case with a cover of glass to permit the working of the mechanisin to be seen and
serving as the insulating support for the third or conversation set of grouping
conductors as specified.
3. Making the glass cover removable and providing means substantially as described
whereby the connections with the conductors carried by the glass are automatically
restored by the act of closing the cover.
4. Mounting each switch with the whole of its propelment mechanism and the
contacts by which electrical connection is maintained by the travelling parts, upon a
separate frame so as to be self contained and removable as a whole as described.
5. The herein described means of removably mounting the mechanisms upon the
base board of the case, and of automatically establishing the electrical connections
with the various parts by the act of placing the mechanism in position.
6. Making the switch propelment screw tubular and housing within it a spirally
coiled spring applied as described for effecting the return motion of the switch.
7. Suspending the cases containing the mechanismis by overhead carriages running
upon rails so as to admit of the cases being closely juxtaposed or separated as may be
required, the grouping conductors of the several cases being in continuous connection
substantially as described.
8. The herein described numerator tape and circuit closing mechanism substantially
as specified.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.