Improvements in Automatic Central Telephone Switch Apparatus.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in Automatic Central Telephone Switch Apparatus.
I, FRANZ NISSL of Zieglergasse 27 Vienna VII Engineer and Electrician, do
hereby declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
This invention relates to apparatus whereby a single main circuit can he
employed for connecting several speaking stations situated at comparatively short
distances from each other to a central station, so as to obviate the considerable
costs and inconveniences arising from the use of a separate circuit for each
speaking station.
This apparatus, which offers the advantage of great simplicity and reliability as
compared with arrangements hitherto proposed for effecting the same purpose,
consists mainly of a switch apparatus which is introduced at a point of junction of
the several line wires of a group of subscribers with the said common main circuit,
and is so
arranged that each of the speaking stations can enter automatically and
consecutively into communication with the central station, which can in like
manner enter into communication with the separate speaking stations without
inconveniencing the other subscribers.
The position for the time being of this switch apparatus is indicated both at the
central station and at the several speaking stations by means either of audible or
visible signs, or by both combined, so that the central station can call separately
any one of the subscribers connected to the switch apparatus, and each subscriber
can, when the turn comes round to him, enter into communication with the central
station, and through this with any other subscriber.
The central telephone switch also contains Brrangements for controlling or
stopping its motion, either from the central station or from a subscriber's station,
and also appliances for automatically putting the same into action again, whereby
conversations of greater duration are rendered possible.
I will proceed to describe the said apparatus in connection with the accom-
panying drawings in which
Figure I shews a diagram of the general arrangement, and Figure 2 a diagram
of the construction of the automatic central telephone switch.
Figures 3 and 4 shew views of detached parts of the switch and its mode of
action, Figures 5 and 6 shew two other modes of action of such a switch ;
Figures 7 and 8 shew diagrams of two devices for giving audible indications of
the shifting of the switch;
Figures 9, 10 and 11 shew a front view, plan and side view of a special
construction of the central telephone switch with the stopping and starting devices.
Figure 12 shews to an enlarged scale the commutator roller of the switch, and
Figure 13 shews cross sections thereof on lines 1 to 12.
Figure 14 shews two views of a part of the releasing mechanism; and
Figure 15 shews a diagram of an arrangement for bringing two separate groups
of subscribers stations into communication without the use of a central station.
As shewn at Figure 1 there is a common main circuit L for a group of
subscribers I II III IV, the number of which can vary according to the average
extent of use of the telephone, such circuit L leading from the central station to
the point of junction K, at which the automatic switch apparatus is applied; from
this the separate lines extend to the several subscribers.
The central telephone switch apparatus situated at K consists of a commutator
which is actuated by a suitable motor so as to bring automatically and consecutively,

page_text: each of the several connected subscribers stations in connection with the common
main line, for a certain length of time.
Figure 2 shews the arrangement of the switch for this purpose, it being assumed
that four subscribers I to IV, are connected to the same. It consists of the discs
or rollers A. B. C situated on one common axis or on 'separate axes and which can
be combined to form a single roller. These discs or rollers are rotated by a motor
and carry contact pieces, which, during their motion, establish consecutively the
connection between one of the subscribers stations and the central station.
The disc A has for this purpose the contacts 1, 2, 3, 4, with which the contact
spring sliding on A, consecutively makes contact, whereby the subscribers I, II,
III, IV are' consecutively put in communication with the main line for a certain
length of time.
As shewn by Figure 3, the position; for the time being, of the spring or
disc A can be indicated both at the receivers at the central station and at those of
the subscribers stations by means of special contacts or interruptions a¹ a² a³ a¹ on
the discs A, a source of current S'being at the same time introduced into the
line L, which however must not influence the indicating apparatus at the central
station.
As by this arrangement the subscriber is not informed of the position for the
time being of the central telephone switch and only receives an indication when
the contact of his apparatus is already made, which would result in imperfect
observation of the indication and loss of time, it is advantageous to provide a
special or ring circuit R, extending from the central telephone switch in such
manner that all the subscribers stations are included in it so that in the latter the
position for the time being of the commutator can at all times be observed.
.١.١٠٠.
For this purpose the secondary coil of an induction apparatus J is included in
the circuit from the spring contact to L, while the ring circuit R contains the
secondary coil of a second induction apparatus 'J'.
"The primary coils of both apparatus J and J' are connected to the current
producer S', the spring contact and seriatim to the contacts 11 21 31 4' of the
rotatable disc B.
..
The contact pieces 1 2 3 4¹ are fixed upon the disc B in such manner as to
have certain relative position to the contact pieces on the disc A, that is to say,
when or shortly before the spring f' comes upon the corresponding contact piece l'
the spring will come in contact with 1 on disc A, and this position will be
indicated in the telephones which are introduced into the secondary coils of the
induction apparatus J J and in the main line L and ring circuit R, by means of
one, two or more sharp sounds at the first second and following contacts, owing to
the inclusion or exclusion of the current generator S.
The receiving apparatus TT TT in the subscribers stations are in this
arrangement connected in parallel in the ring circuit; they could however of course
also be arranged in series..
125
Also, in place of a metallic circuit, earth can be used for the return current, as
shewn at Figure 4.
11
The arrangement can also be such that the ring circuit R is connected to the
primary coil of the induction apparatus J in which case the second apparatus Ji
can be dispensed with; in place of the telephone, galvanometers or other electric
optical indicators can be used for these indications at the subscribers stations,
in 20
In the arrangement, shewn at Figure 5 one induction apparatus is arranged in
the central telephone switch and induction apparatus are also arranged in the
subscribers stations.
41.511571
19.
12
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"The ring circuit R. (with metallic or earth return conductor) contains the
primary coil of the induction apparatus J, the spring, contact of the disc B,
consecutively the contact pieces 1', 23' 4', the current generator S and the
primary coils of the induction apparatus JJ JJ of the subscribers stations.
There may
also be included in the same the galvanometers or other electric
Heel'indingford RD D D
antine
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page_text: וי
The telephones T &c. are in the same circuit that contains the secondary coils of
the induction apparatus J J J J The indications are rendered visible at the
subscribers stations by the galvanometers and audible by the telephones.
The induction apparatus J1 &c. can be so, combined with the induction
apparatus &c. which are under any circumstances required in the subscribers
stations, and the telephones be so combined with the receivers for ordinary
telephonic working by suitable means such as by switches, as to serve for both
purposes.
If the subscriber I (Figure 2) desires to communicate with the main circuit,L,
he puts the telephone T to his ear or applies his ear to the same and waits until
the determined sign for his own station is given; this will be the case as soon as
the current from the contact spring flows through the primary coil of the
induction apparatus J. thence through the primary coil of the other induction
apparatus J to the battery S', and back to the contact 1 and spring.
In all the telephones the corresponding sign will be heard, for example a single
snapping sound which is produced by the introduction and immediate exclusion, of
the current generator S' into and out of the primary circuit. The telephones are
preferably included in the ring circuit by the indicated bridge connection but they
may also be excluded in the position of rest and only be included by the act of
listening at the particular station.
The course of the current in the circuit L is as follows:-
From the contact spring into the secondary coil of the induction apparatus J,
into the main circuit L to the central station, into earth or along a return wire
to E of station I, through the short circuited inductor K' the electromagnet
and the wire to the contact piece 1. of dise A and back to the spring contact f
The central station will consequently also hear the sign for the subscriber I when
the telephone is in circuit. The subscriber I, as soon as he hears the particular
sign, is in a position to enter into communication with the central station.. By
bringing into action the current generator, turning the crank handle of the magneto
inductor, or otherwise producing a current, the subscriber I can call the central
station; similarly the central station can call the subscriber I.
167
The commutator dise revolves with a certain speed in order, that all subscribers
may successively be put in position to call the central station or ice versa.
The duration of each contact is determined according to the number of the
subscribers and the corresponding conditions of working, but is as a rule not
sufficiently long for carrying on a telephonie conversation. Each subscriber must
therefore be in a position to maintain the contact position which connects him with
the main circuit L for a certain length of time.
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For readily effecting this purpose the subscriber can stop the motion of the
commutator for a certain time when his turn, comes round.
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For this purpose the disc, C Figure 2 with its contact pieces 111 2 3 4 16.
provided, which come consecutively into contact with the sliding contact by
rotation of the dise C, this action being made to correspond accurately with the
contacts of disc B.
11. "
The contact pieces 12" &c. are in communication with the corresponding.
subscribers I, II III IV. From the contact spring a wire leads to the electro-
magnet E whose armature a is connected to a disengaging device, so, that by the
motion of the armature this device comes into action and at the same time the
further motion of the discs A. B. C is retarded or entirely stopped....
The armature is for this purpose provided with fork mounted on pivots.p
which fork on the electro magnet E being rendered active, causes the lever H,
which, in a state of rest bears with a stud n on projections on the fork, to
drop off.
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The lever is thus caused to engage with a ratchet wheel S on the axis of the
cominutator so as to stop the motion of the latter.
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If therefore station 1 desires to communicate with the central station, the

page_text: subscriber will at once bring the commutator to a stand still, by sending a current
through the wire ', disc C and contact 1" and through the electromagnet E.
The course of the current is then as follows. From the magnet-inductor K or
other current producer, on the depression of key t¹ to contact 11 spring f" to the
electromagnet E and through the return wire or earth back to the inductor K'.
After the speaking is finished the central station or the subscriber can set the
commutator in motion again; or the clockwork controlling the commutator can be
connected with a current generator which after a certain lapse of time automatically
transmits to the central station the sign for breaking the connection.
But as in the first above mentioned case the one or other subscriber might occupy
the line too long, while in the second case the apparatus would be too complicated,
and the subscriber, in order to hold a longer conversation would first have to apply
to the central station to be reconnected, it is preferable to combine with the
disconnecting mechanism a clockwork which raises the lever H into the normal
position after a certain time, for example 3 or 5 minutes, so that the commutator
can start again.
This is effected, as shewn at Figure 2, by means of a cam e.
If therefore the subscriber requires to speak for some time, he does not ring off;
the central station then maintains the connection, and if no other subscriber of the
same group signals during the interval, the subscriber who is connected up can
again speak for the fixed length of time when his coutact piece comes round
again.
On the termination of the speaking the subscriber rings off in the usual manner.
In Figure 2 the electromagnet E is in the local circuit of the particular subscriber,
and not in the main circuit.
It might however be arranged in the main circuit, as at Figure 6, whereby on the
one hand the number of the requisite wires would be diminished and the com-
mutator simplified; on the other hand however, irrespective of the fact that the
electromagnet would always remain in the line, the motion of the commutator would
be stopped each time the central station signalled which would be disadvantageous
because frequently a subscriber does not reply at once and this interval of time is
consequently lost for the other subscribers."
If namely the central station signals a subscriber with the arrangement as at
Figure 2, the commutator continues to move forward with the determined speed,
and only the subscriber can stop the same, this having to take place before
answering the signal.
If the called subscriber does not at once answer, but allows the contact to move
past, he must wait with his answer until his turn comes round again.
With a larger number of subscribers in each group. the
that with the commutator disc or roller there is combined a phonograph (Figures 7
arrangement may be such
and 8). The respective contact point will then be indicated by a certain sound or
word, or simplest, by the calling of the number, which particularly facilitates
the working at the central station. As it is here only a question of a few regularly
recurring sounds, such phonograms could be easily produced.
The roller B, provided with the corresponding phonograms has a microphone M
placed opposite it in such manner that its membrane is vibrated either directly or
indirectly by means of the microphone and its battery S³ the corresponding sounds
are transmitted into the main line L or through the ring circuit R into the
subscribers stations.
The phonograms on the commutator roller must of course correspond with. the
positions of the commutator plates; they might however, as shewn at Fig. 8 be
employed in combination with contact pieces 1 21 31 41, if in addition to the spoken
word also the before mentioned signs, consisting of a snapping of the telephone or
an oscillation of the galvanometer are to be produced. The arrangement can be
effected according to the diagrams either at Fig. 2 or Fig. 5, and will be readily
understood without further description.

page_text: A suitable construction of the commutator device is shewn at Figs. 12 and 13.
On the cylindrical surface of a roller W of insulating material there are provided,
separate from each other the above mentioned contact pieces for the discs A B C ;
on this roller slide the insulated spring metal strips (contact springs or brushes)
which on the rotation of the roller W come into conducting contact with the
corresponding contact pieces at the corresponding places. The arrangement of the
contact pieces is according to the diagram at Fig. 2.
The sliding contact F corresponds to the contact point marked 10 of B Fig. 2,
and is always in conducting contact with the ring shaped piece C Fig. 12 while
the spring passes over insulated parts of this ring C₁, so that the current is broken
and closed again during certain intervals of time, whereby the before mentioned
audible or visible signals are given.
In the case of the employment of phonographs, the corresponding phonograms
are provided on the commutator roller or on a special roller revolving at the same
speed.
The arrangement of the other contact pieces and sliding springs is such that the
circuits belonging to the corresponding signs are for the time being put in con-
ducting communication.
Thus to the sliding contacts F and fis connected the circuit with the battery S1
and the primary coils of the induction apparatus J and J'; to F, the circuit of
the electro magnet E; to f f f f₁ and ƒ ƒ ƒ₁f the circuits 1, 1, 1, 1, and
of the subscribers and to the main circuit 1, with the secondary coil
of the induction apparatus J.
For example, if the commutator has given the sign for the subscriber I, there
must be connected with the main line the circuit of the subscriber I, and at
the same time also, the circuit of the electro magnet E must be connected with
the local circuit of the subscriber I; this is effected by the contact 11, by means
of the spring contact F1 with L and as 1 is in constant conducting communication
with 27, from 27 to spring f₁ through I, to station I; furthermore, simultaneously
through the contact 1 by means of spring F' to E and, as 1" is in constant com-
munication with 31, from 31 through and ² to station 1.
The contacts 1 2 3 4 and 31, 32, 33, 34 are advantageously made somewhat
shorter than 11 21 31 4' and 27, 28, 29, 30, in order that it may not occur that at
the last moment of the contact on 1 or 2" & c. the commutator be stopped and the
respective contacts 1ª 2 &c. and 27, 28, &c. have already passed their corresponding
contact springa.
The following contact pieces are always in conducting connection:
11-27, 2-28, 3'-29, 4¹-30; 1-31, 21-32, 3-33, 41-34.
The main line is, in the commutator position shewn in Figs. 2 and 12, con-
nected for a certain time with circuit to the subscriber I, and at, the same time
the electromagnet E's circuit is connected with circuit ₁ of subscriber I.
This interval of time depends upon the speed of rotation of the roller W. The
particular subscriber can stop the motion of this rollet for a certain time, after
which the clockwork is automatically released, and the roller continues its
motion.
For this purpose a train of wheels may be employed of which one part is
stopped simultaneously with the commutator, and is then set in motion again.
Greater reliability is however obtained by means of two trains in connection
with each other, as shewn at the central telephone switch Figs. 9-11, where the
driving motion is obtained for example by weights G' and G³, which might
however be replaced by springs or other motive power.
The train L drives the commutator roller W and the train L' contains the
electro-magnet E and prevents, after the releasing has been effected, the further
motion of the train L' for a certain time. One of the trains is consequently always
in motion while the other is at rest.
The weight G'acts on the first motion wheel of the train Lª, and through a
suitable train and through escapement q1 and pendulum p the desired speed is

page_text: obtained for the commutator roller W. The train L' with the first motion wheel 6ª
and the weight G has such a train with escapement and pendulin that
the wheel will revolve once during the interval of time fixed for telephonic
speech.
The arrangement whereby on the release of the train L the train L' is stopped
until the wheel has performed one revolution consists of a three-armed
lever N N N³, fixed on the axis X of the train L³.
The arm Nis so weighted that it tends to turn the axis X in the direction of
the hands of a clock, and when at rest, it lies with its bent chisel-edged end upon
the shoulder g' of the releasing fork g (Fig. 14).
If the fork, which is pivotted at p, be moved to and fro, the arm N¹ will fall,
turning the axis X and thereby the arms N' and N³. The oscillation of the fork
is effected by the current sent through the electro magnet E, the armature à of
which engages with its rod u in a slot of the fork g, as shewn.
The wheel of the train L' bears with a pin against the arm N' when the
train L³ is at rest; on the upward motion of N the pin is released and wheel r¹
and consequently the train L can' turi.
On the axis Y is a two armed lever 01 02 whose arm O' bears with a pin to in a
notch of the disc which rotates with the axis X.
As soon as disc turns, the arm O is raised on its periphery, and the other
arm is moved in the contrary direction to the hands of a clock.
The latter arm is so formed that during this motion it stops the oscillation of the
pendulum p' and consequently the motion of the train L'.
The train L' now remains at rest as long as the train L is in' motion.
When the pins of wheel has reached the hook shaped end of the lever arm N³,
this arm, and with it N N are moved in the contrary direction to the hands of
the clock, whereby the arm N' will be again lifted on' to the shoulder of the fork
and the pin u will again bear against arm N2; at the same time lever arm O¹ falls
into the notch of disc and pendulum p' is released, consequently the train L' is
set in motion' again while L' is stopped.
บ
..
By means of the described central telephone switch apparatus two separate
groups' of subscribers only connected by a commion main line can be brought into
reciprocal communication without the use of a' central' station.
In this case, as shewn at Fig. 15 there is provided in each of the points of
junction K Ko one of the switch apparatus. If for example subscriber I of
group IV desires to speak with subscriber Vo of the other group Io-Vo,
subscriber I first brings the cominutator of switch K to a standstill at the right
moment, whereby he is put in lasting connection with line L, and is enabled, to
hear on his instrument' the signs of the other switch apparatus at Ko. As soon as
the sign of station Vo is heard, subscriber I rings up station Vo; the latter then
first stops the commutator Ko, rings back to I and speech can then take place.
After the prescribed time has clapsed, both subscribers are automatically cut out
again by the resumed motion of the commutators of both switch apparatus, thus
affording other subscribers the opportunity of using the line.
It will of course be understood that the subscribers of one and the same group
are enabled by the central telephone switch apparatus to speak with each other.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. An automatic central telephone switch apparatus for putting subscribers
stations consecutively in connection with a main circuit, consisting of a commutator
composed of one or more revolving contact discs A, B, C, or a roller W,
whose
contact pieces establish communication through a sliding spring consecutively
between each of the subscribers stations and the main circuit, in combination with
a ring circuit R with induction apparatus connecting all the subscribers stations,
the commutator and a local battery being so connected with the said ring circuit

page_text: that the position, for the time being, of the commutator is indicated both in the
main circuit and in each of the subscribers stations, substantially as described.
2. In apparatus such as is referred to in the first claim, the inclusion of the
receiving telephones in the secondary circuits of induction apparatus J and J' or
the combination of the commutator with a phonograph and microphone M, or the
introduction of galvanometer or other optical indicating apparatus B' B' &c. into
the subscribers circuits, for the purpose of rendering the position, for the time
being, of the commutator audible or visible, or both, at the several stations,
substantially as described.
3. In the apparatus referred to in the first claim, the arrangement of induction
apparatus JJ J³ J* in the several subscribers stations whose telephones are
included in the secondary circuits of these apparatus while the primary circuits of
these apparatus and of the induction apparatus J arranged in the central telephone
switch are included in the ring circuit R, substantially as described.
4. In the apparatus referred to in the first claim, the use of a stopping device for
arresting the motion of the commutator for a certain length of time, either at the
central station or at the subscribers stations, such stopping device consisting of an
electromagnet E, whose armature a is connected to a fork g which on the actuation
of the armature causes a locking lever H to engage with a locking wheel Se on the
commutator, substantially as described.
5. In the apparatus referred to in the first claim, effecting the automatic putting
in motion of the commutator after being stopped by the stopping device, by means
of a clockwork mechanism which after a given lapse of time causes & came to
release the lever H from the locking wheel S, substantially as described.
6. In the apparatus referred to in the first claim, the employment of two
clockwork mechanisms L' and L, of which the one actuates the commutator
roller W, while the other is controlled by the electromagnet E and on being set in
motion, stops the motion of the first one for a certain length of time, substantially
as described.
7. In an electromagnetic releasing mechanism such as is referred to in the fifth
and sixth claims, the arrangement of a three armed lever N' N N³ mounted on the
axis X of the clock-work mechanism L', one arm N' of which is held in the
position of rest by a fork g which can be made to oscillate by means of the electro-
magnet E, and a two armed lever O'0' mounted on the axis Y, which lever stops
the motion of the pendulum pl of the clockwork L'and consequently also the motion
of the latter when by the oscillation of the fork g, the lever N¹ N* N* is released
and thereby causes the clockwork L' to be set in motion, while by this motion the
lever arm N is again raised on to the fork and thus frees the said pendulum so as
to set the clockwork L' in motion again, substantially as described.
8. The combined use of two automatic central telephone switch apparatus of the
kind referred to in the first claim, for connecting two groups of telephone subscribers
that are connected by a common main circuit, substantially as described.
Dated this 17th day of October 1893.
ABEL & IMRAY,
Agents for the Applicant.