Improvements in and relating to Switch Devices for Effecting the Connections in Telephone Systems.
Year: 1891

page_text: Date of Application, 13th July, 1891-Accepted, 9th July, 1892
COMPLETE DIEUETUATION.
Improvements in and relating to Switch Devices for Effecting the
Connections in Telephone Systems.
A communication from abroad by JOHANN DIETZ, of Nuremberg, in the Empire
of Germany, Technologist.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agoncy for
Foreign Patent Solicitors, 6, Lord Street, Liverpool, and 6 Bank Street,
Manchester both in the County of Lancaster & 323, High Holborn in the County
of Middlesex, Civil Engineer, do hereby declare the nature of this invention and
in what manner the same to be performed, to be particularly described and
ascertained in and by the following statement :-
The improved automatic central switch in its simplest form is shown in Figures 1
and 2 of the accompanying drawings, and consists of a disc of insulating material,
into the circumference of which there are insorted as many metal pieces as there
are speaking stations to be connected thereto.
Figures 1 and 2 represent an arrangement of switch for use in connection with a
telephone exchange having 12 subscribers. In the centre of this disc there is an
axle which carries a ratchet wheel a and a pointer b. Above this wheel the ratchet-
piece c is placed, movable on the point A and is connected with the polarised
armature d. The ratchet wheel has twice the number of teeth that there are
speaking stations. Further, an electromagnet E is fixed on the disc, the ends of
the wires of which magnet are connected on the one hand with the person calling
and on the other hand with the pointer b. Finally, an earth circuit closer x x is
also provided from the pointer b.
A current interrupter is placed at the speaking station, by means of which the
subsoriber can send current impulses towards the central station. Assuming the
negative pole of the polarised armature d to be at the end over the electromagnet E,
subscriber No. 11 can be connected with any desired speaking place by sending &
sufficient number of current impulses through the electromagnets. The current
passes from the conductor, through the little piece of metal 11, the electro-
magnet E to the centre of the disc and from here through to the earth.
When the pointer is pushed forward to the desired contact, in Figure 1 to
contact 7, subscriber 11 sends a negative current through the switch, the
pointor, the contact 7 and the conductor to the point 7, whereby the alarum in 7
is caused to ring. When the acknowledgement has been received, the conversation
can begin.
When the conversation is ended, subscriber 11 sends one positive current impulse
through the switch whereby armature dis again attracted and the pointer is
turned between contacts 7 and 8; therewith the connection between and 11
is again broken. The earth circuit closer does not unfavourably affect the passago
of the conversation, as it has a very high resistance.
Each speaking place is supplied with the apparatus shown in Figure 5. In this
apparatus, there is the toothed wheel e, the current interrupter, the finger key
for effecting the call, a lever g for hanging the telephone T on, M is the microphone,
Jis the induction coil, and B the battery. The lever has an insulated pivot and
each end of the lever is insulated from the other, being connected with the
positive pole and with the negative pole of the battery B by means of the
springs and respectively.
This lever further carries the insulated metal plato f³.
A catch. engages in the ratchet wheel e, which also has an insulated piece of
metal. The ratchet wheel itself has twice as many teeth as there are speaking
places, and each second tooth has a number which corresponds to the similar

page_text: number on the switch disc. If the subscriber desire to adjust his switch disc to
any particular number, it is only necessary to turn his ratchet wheel until the
desired number reaches the catch i, as, by this manipulation, exactly as many
positive current impulses are sent through the conductor to the switch as is
necessary for adjusting the disc to the required number.
The electric current passes then from the positive pole of the battery to the
spring through, the contact, the ratchet wheel e, the catch i, the pins
and (as, by the revolution of the ratchet wheel e, the catch i is raised by its
teeth and the pin is pressed on the spring K') to the conductor and from
thence to the switch, whilst the current from the negative pole of the
battery runs to the spring, the metal niece, the contact and to the
carth.
If the pointer on the switch has been moved forward to the required number,
the negative current requisite for calling is thereby simply forwarded to the place
to which it is desired to call by pressing down the lever f by means of a finger
key. Thereupon the electric current goes from the negative pole of the battery
through the springs h³, the metal plate, the contact K to the line, whilst the
positive current from the positive polo is conducted through the spring h', the
metal plate and the contact K to the earth.
When the reply is received, the telephone is taken off the hook whereby both
telephone and microphone are connected for speaking.
When the conversation is completed, the ratchet wheel e or the pointer of the
switch apparatus must in no case be placed back in its original position, but must
be only moved forward about one tooth.
4
The single switch discs are arranged one behind the other, and, in fact, each
one of the same numbers conducting to one another of the whole of the discs is
connected, as also each speaking place is connected with its corresponding contact
number.
Figure 2 represents a side view of such a disc, on each side of which a
switching apparatus is placed, so that thereby one disc suffices for two
subscribers.
Figure 3 represents a sketch of a conductor for six subscribers. By this
arrangement, and 3, for instance, speak together, as well as 2 and 6. Actually,
however, the wire conductor is simpler than those shown in the sketch, as the same
mutually conducting contact numbers are simply connected by a metal band, and
from this metal band the conducting wire leads to those stations of which the
contacts bear the numbers.
If the number of subscribers attain such a pitch that a single disc no longer
suffices, each subscriber has (Figure 3), at the central station, instead of one disc,
a suitable number of the same.
Figure 4 shows, for instance, such a developed connecting device in which each
disc (I, II, III, IV and V) is intended for each 100 subscribers.
The armature of the small disc is negatively polarised, that of the
dises I, II, III, IV, V, positively polarised.
The calling subscriber, by means of a positive current impulse, places the
pointer of the smaller diac on tlie desired disc, and by means of a negative impulse,
the pointer of the corresponding larger disc is placed at the required number.
The call in this case must be offected by means of an alternating current.
In the latter case, each speaking place is supplied with the apparatus shown in
Figure 6. This consists of the two adjustable discs e¹ and with the
catches and, each of which again has an insulated metal bush m' and m³
respectively.
By turning the ratchet wheel e, positive current impulses, and by turning e³,
negative current impulses are sent towards the switch. In the first case, the
electric current goes from the positive pole of the battery. B to the ratchet
wheel e¹, through the catch, the pin A, the spring & (as, on the turning of the
ratchet wheel, the pin A¹ of the catch it comes in contact with the spring ) to the

page_text: line, whilst the negative current from the negative pole is conducted to the earth
through the ratchet wheel e³, from the axle of this through the catch to the
metal bush m', and from here through the contact (which contact is also actunted
by the revolution of the wheel).
In a similar manner, by revolving the ratchet wheel.e', negative current impulses
may be sent to the switch. The call takes place by means of an alternating
current which is produced by an induction apparatus, for which purpose the
induction coil J is provided with an iron core and a cut off catch. The current
thus goes from the minus pole of the battery through the spring *, metal piece f³,
contact (through the pressing down of the signal knob ), the primary wire 11
of the induction coil J, the cut off catch L, wires 3 and 4, contact and
metal picce ', and wire 5 to the positive pole. The alternating current produced
passes from the secondary wire 22, of the induction coil, through the telephone T,
contacts, k, to the line, whilst the other end of the secondary wire leads to
the earth.
In order that the switching discs may not be set in motion through alternating
currents of the call, the electromagnets of these discs are wrapped with corre-
epondingly strong wires so that any attraction of the polarised armature is
prevented.
When the reply has been received, the telephone is taken off the hook, whereby
the telephone and microphone are connected up. In order that the current of the
microphone may not bring the cut off catch into action, the stop catch Lis
polarised, so that the positive microphone current does not act on the same, but the
negative current produced on pressing down the finger key does.
When the conversation is ended, the disc e' must be brought back to its original
position. In order now to prevent the disc e' being turned before disc e² is brought
into its original position, both ratchet wheels have only a single crank which,
for instance, is suspended on a chain and an arrangement is adopted by means
of a disc seated on the axle of the wheel e, so that the crank fixed at e' may
be only drawn out and inserted into e' when has come back to its original
position.
By the above described arrangement of the central switching station, disturbing
side currents are not entirely excluded. In order also to entirely avoid such side
currents the central switch station is arranged in the manner described hereinaftor
and shown in Figure 7.
The ratchet wheel of the switching disc is not actuated by a direct current but
by means of a relay, further, the switching disc is provided, in addition to the
electromagnet E already described, with a second electromagnet E', together with
the armaturo o belonging thereto, and this latter arrangement serves for the
purpose of breaking the connection with the pointer Z shortly before the moment
when the closing of the circuit for actuating the ratchet wheel is accomplished.
The relay which is provided with a counter, coil, is formed of the two poles el
and el, which, for the purpose of being easily seen, are shown in the drawing as
if they were situated one beneath the other; e is the positive part of the relay or
that pole which is actuated through the positive current, whilst e" represents the
negative part.
The switching is effected by means of the arrangement before described and
shown in Figure 7 on the drawing in the following manner :-
The person at the telephone, who is going to make the call, sends first a certain
number of positive current impulses through its conductor. The positive part e¹
of the relay is thereby influenced, and then, through the electromagnet E', at ench
current shock, the connection with the pointer Z is interrupted, whereby the
ratchet wheel gradually adjusts, by means of the relay current, the pointer in the
manner described in Figures 1 to 6 to the desired contact number.
The positive current flows away from the line through the relay e¹ell to the
earth.
! In consequence of the above described operation, the lever a¹ approaches to

page_text: the positive pole e and thereby the passage of the current of the battery B¹ is
established.
This current then flows from the positive pole of the battery B¹ to the spring c¹
and from this latter through the lever a', the contact spring and the electro-
magnet E. In consequence of this, the lever o' is attracted by the electromagnet E¹
and is thus placed out of contact with the contact piece p', and thereby the
conducting connection with the switch pointer Z is interrupted.
Shortly after the closing of the circuit, brought about by means of the contacts c¹
and ', a second circuit is completed through the contacts and, which are
connected with the lever a¹ or the electromagnet E, which latter is so arranged
that it can only encounter rafter d'.
The ratchet wheel and the electromagnet E are influenced through this second
closing, and in such a way that the closing of the current through d always takes
place before that through, and the connection with the switch pointer is each
time interrupted before the moment when the electromagnet E of the local
battery B receives a current impulse for actuating the switch mechanism."
The call follows through the negative current, by means of which, in this case,
the negative relay pole el is actunted, and thereby the lever is attracted.
8
In consequence of the turning of the latter, the contacts y¹ and h¹ or i¹ and A¹
are connected with each other by means of the metal ends s and of the lever.
The insulated metal plate n' is simultaneously lifted from the contacts and m³,
and thereby its connection is interrupted.
The negative relay current then goes, in consequence of this, through,,, the
lever o', contact p' and switch pointer Z to the place to which the message is to go,
whilst the positive current passes through h, a', and s to the earth.
Now in order that the relay may not be actuated in sympathy through the reply
current, which is also negative, of the telephone receiver communicated with, it is
provided with a countor coil, so that the reply current cannot influence the relay.
The reply current passes; therefore, from the line of the answering telephone
receiver through Z, through m³, n', l', the relays ell, el to the calling telephone
receiver; at the same time, however, a current of the same strength flows through x,
the contacts,, and the counter coil ly to the earth. As the same current
of similar strength now traverses the relay in both directions, the penetration of
any free magnetism into the relay is prevented. Thus the reply current reaches the
calling receiver whilst the current traversing the counter coil is led off into
the earth.
The contact pieces" and ", as well as the connecting piece n", are for the
purpose of cutting off the counter coil while the call is being made. It is preferable
also to introduce the two resistances W and W', of which W₁ serves to oppose
such a resistance to the switching current as well as the calling current that the
major part of these currents is conducted to the earth, so that thereby the relay
at once comes into action whilst the smaller resistance W is intended to limit as
much as possible the circuit through the earth of the armature current.
Having now particularly described and ascertained the nature of the Enid inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is:-
1. An automatic central switch for telephone use in which, by means of the
current impulses sent into the conductor by the person calling, a ratchet wheel is
set in graduated motion in a given direction with the aid of an electromagnet
having a polarised armature, which moves a closed circuit indicator over a circuit
closer arranged on the circumference of a switch disc until the call is effected by
the contact of the circuit closing piece on the receiver of the place called on with
the indicator by means of a current sent from the opposite direction by the person
at the telephone who is making call.
2. The modification of the switch described in Claim 1 for use in the working.of
large telephonic systems, in such a way that, for each connecting wire, a main

page_text: switching disc is employed, the circuit closing pieces of which are connected with
each one of the switch discs arranged for a given number of the remaining
connecting conductors, whereby the connection of the conductor at the calling end
with that at the receiving is brought about in such a way that the adjustment of
the indicator of the main switch disc through current impulses from one direction
causes the movement of the indicator of the group of discs through current
impulses in an opposite direction and the call is made by means of an alternating
current.
3. In the automatic central switch described in Claims 1 and 2, the arrangement
whereby the ratchet wheel is not actuated by a direct current, but by means of a
relay, and, further, the introduction of a second electromagnet, as well as of two
circuit closing pieces d' and f1 coming successively into contact with the lever a'
for the purpose of breaking from time to time the connection with the circuit-
closing indicator for guarding against injurious outside currents, before the
ratchet wheel is set in action, and finally the arrangement of a counter coil on
the relay by means of which any free magnetism developed in the relay by the
reply current is lessened.
DLL 1 T.... 1001
WM. P. THOMPSON & Co.,
Agents for the Applicant.