Improvements in Switch-boards for Telephone Exchange.
Year: 1889

page_text: Date of Application, 27th July, 1889
Complete Specification Left, 27th May, 1890-Accepted, 27th Sept., 1890
PROVISIONAL SPECIFICATION.
Improvements in Switch-boards for Telephone Exchange.
We, Mix & GENEST, a Limited Company of Berlin S.W. 14A Neuenburger St.,
Germany, and WILLIAM OESTERREICH Engineers 14A Neuenburger St., Berlin S.W.
do hereby declare the nature of this invention to be as follows:-
The switch boards now in general use for telephone exchange require a contract for
each subscribers line at each section of the board, and there is a local test wire
connecting the metallic body of the spring jacks, by means of which the attendant
can ascertain whether the called line is engaged or not.
The employment of two wires for each line causes, in a large exchange, considerable
expense and our invention has for its object to do away with the test wire and thus
not only saving about half the wire but also simplifying the construction of the
switch-holder.
According to our invention each switch hole consists merely of two conducting
portions, a socket and a spring lying against and insulated from the former by means
of ebonite or the like.
The wire passes through a number of switch holes and after the last switch hole an
indicator and a test battery as well as a small adjustable resistance for regulating the
current are inserted.
For testing purposes the galvanometer can be inserted into the line by a plug, with
double connecting cord.
The testing plug consists of a metallic body shaped towards the end as a shoulder
neck and head. The body is surrounded by an insulating tube and the lower portion
of the latter is in its turn surrounded by a metallic tube, from which as well as from
the central metal body, issues connecting wires.
The length of the switch hole and of the plug correspond with each other in such a
manner, that when the plug is inserted into the hole, the head lifts the spring with
which it then has contact while the metal cover has contact with the switch-tube, so
that a galvanometer inserted between the wires of the plug is circularly connected and
if it indicates a current, the whole line must be free.
The connecting plug consists of a metal cylinder ending in a head and provided
with an insulating ring just beneath the head, forming the neck. A connecting wire
is fastened to the end of the plug. If the plug be inserted sufficiently far for the edge
of the switch hole to he against the insulating ring, then the wire is connected.
London, July 27th 1889.
C. R. BONNE & Co.,
Applicants' Agents.
COMPLETE SPECIFICATION.
Improvements in Switch-boards for Telephone Exchange.
We MIX AND GENEST LIMITED and WILLIAM OESTERREICH, of Neuenburgerstrasse,
Berlin, Germany, Electrical Manufacturer and Electricians 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 :-
In the multiple switch boards hitherto used in central telephone exchanges, the
arrangement has been that besides the wires which run through the entire board from
one contact spring to another, yet another wire is provided which connect the main
bodies of the individual springs with each other, this latter being the so called
test wire

page_text: The first mentioned wire connects the subscribers main line with each respective
switch board, contact being first made between the first switch board and the main
line, another wire leading to the second board and so forth through the entire system.
In the last switch hole of the system the contact is connected with a signal or alarm
from which the conducting wire leads the current to earth.
The second mentioned wire which as above stated is utilized for testing purposes
extends from one contact point to another of the switch holes in a corresponding
manner to the wire connected with the main line. This arrangement renders it
possible for the attendant in charge of the switch board at the exchange to state
whether there is at any moment a connection already established between any
individual switch.and the main conducting wire.
But by the adoption of the arrangement constituting the essential feature of the
present invention, which are described in this specification and illustrated in
Figures 1 to 8 on the accompanying sheet of drawings a very considerable simplification
of the above described arrangement is effected.
The testing wire is in the first place dispensed with altogether, and this enables the
switch holes and their connections to be also simplified in construction. Thus the
switch which in other existing switch boards, actually consists of three distinct parts,
are, in the switch designed according to this invention, composed only of two parts, so
that a large saving in the space occupied, as well as economy in cost of the apparatus 18
hereby accomplished.
To enable the invention to be clearly understood, the several figures and letters of
reference marked upon the annexed drawings are hereinafter referred to.
Fig. 1 represents in the form of a diagram the arrangement of our improved
multiple switch board with annunciator or drop K and battory B.
Fig. 2 shows the arrangement of the switch hole in cross section longitudinally in
the top part of the said figure and in top plan view in the bottom part of the figure.
The arrangement or construction herein shown comprises a tube or cylinder a and
in connection therewith the termination aº, which latter part a serves for the purpose
of fastening the switch in the board of the exchange, into which the plug is required
to be inserted. The contact spring 6 is insulated from the tube a, at the end marked c
by means of a piece of ebonite or similar material but is in contact with such tube at
the point d. It is thus evident that the extra contact piece for establishing connection
which has hitherto been employed in the switch holes of multiple switch boards is in
this way no longer required.
The plug of the switch hole is represented in Fig. 4. It consists of two metallic
parts & which are insulated the one from the other but each one is in contact with
the conducting wires s and s¹ respectively. The part extends through the whole
length of the plug and is isolated from the part by means of the tube n which is
composed of ebonite or other similar insulating material. It is also provided with the
groove or recess m.
Upon the insertion of this plug into the switch hole represented in Figure 2, the
contact spring of the switch hole is lifted up by the entrance of the head or part K
of the plug, and when the part K has been inserted far enough into the switch hole,
the downwardly bent portion o of the said spring brests in the groove or recess m in
the plug.
By this movement the plug k is firmly secured in its position in the switch hole.
At this time there is no contact between the spring band the tube or cylinder a at
point d but the spring 6 is in contact with the head of the plug K and the interior of
the cylinder or tube a is in contact with the tubular part of the plug. Upon forcing
the plug still further into the tube or cylinder a, the part o of the spring 6 is released
from the groove or recess m in the plug, and rests or presses upon the insulating
or ebonite tube n thereof. The spring b is thus insulated from the plug as well as
from the cylinder a and the cylinder a is only lett in contact with the part k and
therefore with the conducting wires in connection therewith.
The plug thus takes, in being worked, two different positions. In the first position,

page_text: that is when the plug is inserted half way into the switch hole, the cylinder a. and the
spring bare in contact respectively with the conducting wires s and s' between which
in an intermediate position is inserted the galvanometer.
But in the second position, however, that is when the plug is fully inserted into the
switch hole, the head or front part k of the plug, as well as the conducting wire s'
attached to it, are quite insulated whilst the tube a remains in contact with the
conducting wites by means of the part of the plug.
The conducting wire L shown in Fig 1 coming from a subscriber, to the exchange
leads through the switch hole I in that figure to the tubular part a and this is now in
contact with spring & the latter being at the same time in contact with a' of the next
switch hole through the conducting wire 1, leading thereto.
The spring of the switch II is similarly in contact with the tubular part a³ of
switch III through the conducting wire and the spring of the switch hole III is
in contact with a³ of switch holo IV through conducting wire 12, this arrangement
'being continued throughout the system and terminating in the resistance W through
annunciator K. and battery B to earth.
The arrangement of the last contact switch is represented in Figure 3. The shell e
has two ebonite or insulating pieces c at one end, and also an ebonite or insulating
portionat its other end. Two springs & fare attached to the ebonite pieces c and
the spring bis in contact with the tubular part e by means of the part d and is
provided upon its inner surface with a piece of ebonite or insulating material ?.
The contact spring frosts or presses upon the ebonite pieco and is thus insulated
when at rest For making contact with this switch hole the plug shown in Fig. 5 15
to be employed, and this plug also admits of two distinct positions being occupied in
the process of its insertion. Thus when the plug shown in Fig. 5 is inserted into the
tubee Fig. 3 for a certain distance, the inwardly bent portion of the contact springf
becomes fixed in the groove or recess m' of the head or front part (Fig. 5) whilst
the piece of ebonite or insulating matenal upon the inner surface of the contact
spring is forced into contact with the head or part kl, the contact spring being in
contact with the part of the plug and thereby with the conducting wires in
connection with the said part . The part 6 is insulated, when the plug is in
this position and also when the plug is still further inserted into the switch hole;
but upon this further insertion tho bent part of the contact spring frests upon n this
contact spring is then also insulated and only the conducting wire is in contact with
the tubular part e by means of part of the plug.
The plug shewn in Fig. 5 inserted in the last switch hole of the series is now in
contact with the plug (shewn in detail in Fig. 4) of the adjacent or other switch holo
by means of the conducting wires s' and s² and the conducting wire s is also in contact
therewith through the intervention of the sensitive galvanometer G in the circuit. It
is evident than any other current testing appliance may be subsututed for the sensitive
galvanometer G if preferred. The contact spring of the last switch hole of the
entire series is connected with the transmitting instrument in use by the attendant in
charge of the exchange and Fig. 6 shows the arrangement of the conducting wires
coming from the subscribers A and B through wires L and L.
As long as no plug is inserted the linos Land L' would both be connected to the
earth by means of circuit passing through spring b, annunciators K K' and the
battery Z common for the various circuits. Suppose now that A calls the station then
the flap at K would drop. The attendant now inserts the plug shewn in Fig. 5
sufficiently far into switch hole IV for it to attain its first position whereby the indent
of spring adjusts itself to the corresponding indent in the plug head ¹ and the
circuit between the wire L and the speaking apparatus of the attendant is thereby
established. Furthermore the flap & is out of circuit because of the spring & being
raised by the plug from its contact position and insulated by the ebonite piece i and
subscriber A can thus speak with the station attendant.
If now A demands to speak to B the attendant has to ascertain whether the line L',
which connects B with the station is free. This test is done by means of the plug
shewn in Fig. 4 which the attendant inserts in a switch for L'. In Fig. 6 it is

page_text: assumed that the plug is inserted in switch hole II but the action throughout
remains the same whether the plug is inserted in this or in any other switch hole
of the series.
The plug must be so far inserted that the inwardly bent portion o of the contact
If the line 15 free then all 5
spring brests in the groove or recess of the plug head Z.
the springs rest upon the shell a and a current passes from battery through
annunciators K' into wire-L by way of spring b of switch III and through the head k
of the plug, through the conducting wires to galvanometer G, which is, as will be
seen, in the circuit between the end of the plug and the cylindrical part of the
switch hole. But if, on the other band the conducting wire is engaged and con- 1
sequently any one of the springs b raised no effect will be shewn by the galvanometer
and the plug will then he removed by the attendant.
The -plug-marked 5 in Fig. 6 is also connected through the line wire s² to the
galvanometer, so that a part of the current will pass through the wire s' into the
transmitting apparatus; and another part through the wire leading to earth, but
this current does not interfere with the galvanometer, and consequently not with
the result of the test which has to be made. If through the indication given by
the galvonometer it is clearly shown that the line wire L is free the attendant
pushes the plug further home, into its second position in which the spring b is in
contact only with the insulating ring n of the plug and the conducting wire s' is
therefore out of circuit and the respective line connecting A and B by way of s²s are
connected.
The subscriber A is now communicated with, and when the plug 5 (Fig. 6) is
pushed home into its second position the transmitting apparatus of the attendant is
switched out. As the current travels from L' by way of s, G. and to L the
galvanometer G always remains prepared to receive the finishing signal. Should it
be undesirable to have a battery in the exchange as represented by Figs. 1 and 6, the
same result may be effected by the employment of a condenser (which is indicated by
the letter e in Fig. 7) in the line wire at the rear of the telephone instrument.
This last instrument is generally suspended upon a hook at the extremity of lever f
which swings around the point s*. Through the weight of the supported instrument,
fx is kept in touch with the contact *, the current from which is conducted to earth
over a resistance W., On the removal of the telephone instrument F from the hook,
the passage of the current to earth is interrupted through the lever fx falling (through
its own weight) whereby contact is established at a*.
This method of switching can be applied both in connection with the transmitting
and the receiving instruments. It has the advantage of causing a very considerable
decrease of the interfering noises produced in long single conducting wires, which
tend in existing arrangements to interrupt the clear understanding of the conveyed
message at the receiving end of the line.
Fig. 8 shows the form of plug which is to be employed in this latter connection. It
consists essentially of two parts, marked and the first being of metal and the
second of an insulating material, and in the conducting wire of which is inserted a
testing galvanometer and a battery with ground connection. Upon the insertion of
this plug into the tube a (Fig. 2) ³ is connected by a whilst b is isolated through kª.
If no current be apparent then the line would be occupied.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we hereby declare that we
claim as our invention :-
1. In multiple switch boards for telephone exchanges the arrangements by which a
battery can be used for testing, so as to dispense with the usual separate test wire,
consisting essentially in the special construction of the parts forming the switch hole
substantially as described and as shewn in the drawings.
2. In-such switch boards the specially constructed switch-hole consisting of a metal
cylinder with 2 movable springs of which the one when at rest 13 in contact with the
cylinder while the other when at rest is insulated from it, the former being provided

page_text: with an insalating attachment substantially in the manner as and for the purpose
described.
3. The insertion of a current tester or galvanometer between lines sand & from plug
in Fig. 4 on the one hand and line from plug in Fig. 5 on the other hand,
substantially in the manner as and for the purpose described.
4. In such switch boards the testing of the circuit from the station by means of a
plug the metal part of which carries an insulating head and in the circuit of which
is inserted a current tester and a battery with earth connection substantially as
described.
Teted 92-dd 1800
C. R. BONNE & Co,
Authorized Patent Agents, 41, Eastcheap, E.C, Agents to the Applicant.