Improvements in and relating to Electric Telephone Systems.
Year: 1894

page_text: Date of Application, 25th June, 1894
Complete Specification Left, 23rd Mar., 1595-Accepted, 8th June, 1895
PROVISIONAL SPECIFICATION.
Improvements in and relating to Electric Telephone Systems.
I, HENRI NOEL FRENAY-OLYFF, of 64 Rue Dailly, Brussels, in the Kingdom
of Belgium, Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to electric telephone systems and has for its object to
simplify the arrangement at the central station and also at the stations of the
subscribers.
In principle the improved arrangement differs from the installations heretofore
used in that the operation of all the apparatus and accessories serving for the
transmission of the call signals and for putting two subscribers in communication is
effected by breaking the circuit, contrary to what takes place in the systems hitherto
employed where these apparatus and accessories are operated by the closing of the
circuit or by sending transient currents through the line.
Now the improved mode of intercalation, with a permanent current, of the parts
for the intercommunication leads to the suppression of a considerable number of
these parts at the station of the subscriber and to a remarkable simplification of the
connections to be established at the central station.
I may recapitulate the various operations to be effected between the subscribers
and the central station, which consist in signalling to the central station the call of
a subscriber by disengaging the shutter of an annunciator; in putting, by the
introduction of a plug into the jack and by the operation of a key, the operator in
communication with the subscriber who calls in making sure, by means of the test.
line, whether the subscriber called is not connected at another table; in connecting
this subscriber then at the table of the operator by the introduction of the second
plug into the corresponding jack and in calling him by switching the call generator
into the line; in connecting the two subscribers by the operation of the key which
at the same time puts in circuit the annunciator of the end of the conversation
by insulating the post of the operator.
In considering the most complete installations, that is to say those where the
central station is provided with a multiple switch board 1 may state that the
essential simplifications which result from the improved arrangement, characterized
by its operation by the breaking of the circuit, consist at the central station in the
suppression of the test line, and at the stations of the subscribers in the suppression
of any current generator or other intermediate devices concerning the call, all the
accessories relative to these functions being transformed in consequence, with the
exception of the call generator at the central station and its accessories, and also
the telephone post of the operator, which undergo no changes and operate as in the
systems heretofore used by the closing of the circuit.
I may suppose the employment of commutators with jacks to be universally
adopted at the central station, and these apparatus have scarcely to undergo aur
changes for the improved system.
In the first place I will deal with installations without a multiple system for a
single-wire network and then pass on to the multiple systems and double-wire
networks with or without multiple boards.
In the arrangement heretofore used for calling the central station the subscriber
has at his station a magneto current generator or battery by which he sends
currents through the line, at the end of which is at the central station an annunciator

page_text: connected directly with the earth to ilisengage the shutter for exciting the electro-
magnet which attracts the armature and raises n stud.
In the improved arrangement the current generator is dispensed with at the
subscriber's station and replaced by a source of electricity (some elements of
battery) at the central siation and common to all the subscribers, this source of
electricity being included between the amminciators and the earth likewise common
to all the subscribers. In this system the current obtained from the central source
is permanent and keeps the shutters of all the annunciators engaged by the
attraction of the armatures whose studs traverse the shutters. For disengaging
them the circuit must be broken, because then the armature ceasing to be attracted
the said stud drops and enables the shutter which is no longer retained to fall down.
This therefore gives rise to but a slight modification in the annunciators hitherto
used, whilst on the other hand I effect a saving of all the call current generators at
the subscribers' stations. The call devices are replaced at the subscriber's
station by a simple interruptor.
The interruptor may be actunted either by a button upon which the subscriber
presses, or also in an automatic manner by unhooking the telephone.
When use is made of the interruptor the line in which the receiving bell is
included passes to earth through the hook of the telephone and the interruptor
whose button it is sufficient to push in order to break the circuit and disengage the
shutter from the annunciator at the central station. The receiving bell operating
only under the action of alternating currents may be inserted into the circuit of
the battery at the central station without inconvenience.
In case the interruptor is suppressed and the circuit is broken automatically by
the unhooking of the telephone the post is so arranged that the line circuit will to
connected to the bell by the hook itself, the bell being then inserted between the
latter and the earth.
The call having been transmitted by the subscriber the operator insulates the line
from the call signal and from the earth by introducing one of the plugs of a pair of
intercommunicating cords into the jack corresponding to this subscriber. He thus
pots this subscriber in communication with his post by the operation of the key
which he has for this purpose. Then he introduces the plug of the second cord into
the jack of the subscriber with whom it is desired to communicate and he calls him
by connecting with the line of this subscriber the circuit of the alternating current
generator by pressing a button. Then he insulates his post by the operation of the
key, leaving the two subscribers in communication; he waits until the annunciator
of the end of the communication is disengaged, which he has placed in the circuit of
the subscribers by the displacement of the key inserted between each pair of flexible
cords.
According as this key occupies one or the other position there is in the circuit of
the cords either the annunciator of the end of the conversation or the microphone
of the operator cabling him to communicate with the subscribers either by
speaking to them or by exciting their receiving bell by connecting the circuit of
the alternating current generator to one or the other line by pressing the
corresponding buttons.
When in the arrangement heretofore used the operator displaces the key from
one of these positions to the other the circuit of the annunciator of the end of the
conversation will be interrupted which can therefore operate only as long as it is put
in circuit by an operation of the key. In the improved system this interruption
must not be able to take place, because it would have the effect of unduly operating
the annunciator of the end of the conversation, which is operated in the same
manner as the call annunciator, that is to say by the breaking of the current due to
the operation of the subscriber pressing the interruptor. In this ense the old key
could not therefore be used and it must be completed so as to keep the circuit of
this annunciator always closed. This is obtained in a very easy inanner by providing
the key with two contacts, a third contact always connecting the circuit to the
battery even when the two contacts communicate with the operating post; while

page_text: these contacts connect.the circuit of the annunciator to the line by the operation of
the key when the operating telephone is put out of circuit. The key has preferably
the form of a sector made by wood or ebonite, adapted to turn upon its centre and
carrying at its peripheral part the three contacts sliding alternately upon six springs,
the first pair corresponding to the call signal, the second pair to the call buttons,
and to the cords, and the third pair to the operating post. A call generator and
buttons or contacts, are provided which enable call currents to be sent through the
flexible cords through plugs on the lines.
The application of the permanent current arrangement to the multiple system
renders it possible, as already stated, to suppress the test line and to retain no other
connections than those which unite together at all the tables the jacks of the same
subscriber.
In fact the independent test line connecting the body or fixed part of the jacks
was indispensable in the system heretofore used.
Now in the improved system the call signals are in a closed circuit and there is no
inconvenience in directly connecting the second spring to the body or fixed part of
the jack, and this arrangement considerably simplifies the installation. On the other
hand if under these conditions 1 introduce a plug into the jack the circuit of the
subscriber is broken and the call signal would be disengaged if the circuit could not
be connected to other earth than that of the subscriber. This can be obtained in a
very simple manner. Wires are connected to the call buttons and the key of the
table and flexible cords carry the plugs. The plugs and cords have a double circuit
and the second of these circuits is permanently connected to the earth. The second
circuit of the plug connects the body or fixed part of the jack, while the first circuit
corresponds to the first spring of the jack and consequently to the subscriber.
Therefore even before this circuit is broken to the annunciator by the raising of the
spring it is closed by the body or fixed part of the jack connected to the second
circuit and to the earth common to these circuits. In this manner the circuit formed
ly the body or fixed parts and the connections between their jacks may therefore be
broken at will without inconvenience for the annunciation, and all the wires of the
test line of the system hitherto employed are suppressed.
To make sure whether the circuit has been broken by the introduction of a plug
at any table before giving communication to a subscriber it is sufficient to send
through the said circuit weak alternating currents for example by the aid of a small
magneto machine or small induction coil susceptible of producing a certain noise in
the telephone of the operator when the latter touches with the extremity of a plug
the body or fixed part of one of the jacks of the line, which noise is heard as long
as the circuit is not broken, but which ceases to reach the ear of the operator
as soon as the circuit is broken. Suppose for instance the communication to be
established with the second table as has heen stated, the body or fixed part and the
second strip of the jack are then put to earth, and the extremity of the plug is in
relation with the upper spring of the wire of the subscriber.
If the operator of one table wishes to take this subscriber and if by means of a
plug he touches the body or fixed part of the jack he no longer hears the noise of
the magneto machine. If it is the operator of another table he does not hear the
noise either, the body or fixed part being put to earth and the derived current to
the operator much too weak to enable the noise of the magneto machine to be
heard. When therefore the operator hears the noise of the magneto machine
through the jack touched, the subscriber is free, and he is occupied when the noise
is no longer heard.
If in the simple or multiple systems I wish to reduce the number of elements
necessary for the operation of the annunciator of the end of the conversation it is
sufficient, instead of having this annunciator and the battery in tension, to put it in
derivation.
The annunciator is constructed and regulated for operating by a current of given
intensity, and this intensity is reached in the circuit of the annunciator only at the
moment when the subscribers, having finished speaking, interrupt their line and,

page_text: thus insulating the second derivation connected to the battery by these lines, canse
the whole current of the battery to pass through the annunciator.
The application of the system with a permanent circuit to double wire networks
comprises the same simplifications as herein before described, and it may be easily
realized by some insignificant constructive changes to be made in the jacks, plugs
and their connections.
With the single-wire networks, the jack has two ships. The only change to be
made therein consists in connecting the second strip to the body or fixed part of the
jack by a temporary contact which at rest connects the line to the bell and the
earth. If the subscriber, in order to ring, unhooks the telephone he breaks
the circuit, the current from the battery at the central station ceases to pass
through the call signal and the latter operaies. The arrangement at the subscriber's
station is extremely simple. The bell at this station is then insulated and the
apparatus for the conversation is put in the closed double circuit at the central
station by the introduction of the plug which insulates the second strip of the jack
by removing it from the contact.
The arrangement of the jack is such that when the plug is introduced
three-quarters it comprises three circuits the first of which is put in connection with
the earth. When the plug is introduced the first contact must take place so as lo
put one of the strips to earth before it is moved away from the said contact in order
to obvinte the operation of the annunciator. By pushing it then home the second
contact of the plug closes by another strip the circuit through the line in the same
manner as it has already closed the same by the third contact through the other line
by the body or fixed part of the jack.
The manner in which the plug is connected to the operating apparatus does not
require any supplementary explanation.
Instead of a plug with three circuits use may be made of a plug with two circuita
but in this case a third strip is needed in the jack for the purpose of putting the
annunciator to earth.
In this arrangement the form of the plug is the same, but the third strip of
the jack permits the suppression of the circuit which it replaces for putting
the annunciator to earth the extremity of the plug putting the second and third
strips previously in circuit.
Then the operations take place as follows: For ringing at the central station the
subscriber unhooks his telephone, interrupting by this operation the circuit at
the central station, by introducing the plug into the jack for putting to earth the
annunciator by its first contact.
The first strip is put in communication with one line and the body or fixed part
of the jack with the other line. The circuit is then closed at the central station
upon the post of the operator. The subscriber called is rung in the ordinary
manner. By operating the key the annunciator of the end of the conversation is
inserted in derivation upon the two lines.
When the conversation is finished it is sufficient for the two subscribers to hang
up the telephone for automatically breaking the circuit and consequently stopping
the operation.
For the application to the multiple system the jack receives outside the contact a
second contact corresponding to the first strip, while the plug remains exactly as
set forth.
11. has thus the effect of putting the second to earth by its circuit and then
putting by the other contact the third strip in communication with the second strip
and the body or fixed part of the jack with its circuit.
The connection of the plug with the operating devices is as follows:-
The bobbin of the microphone comprises three circuits, one of which is connected
to the circuits of the two plugs. This arrangement serves to realize the test line.
When a subscriber called is not in communication, and the orifice of the jack is
touched a noise is heard in the telephone due to the battery whose current passes
through an annuncintor the strips contacts and bodies or fixed parts of the jacks
through the circuit of the plug with which is operated and lastly through the third

page_text: circuit of the bobbin so that a current will be induced in the telephone. If on the
contrary the subscriber is in communication this circuit is broken and nothing is
heard.
The suppression of the test line is therefore realized by the arrangement in
consequence of the jacks and of their plugs with the same facility and simplicity for
the double wire networks as for single-wire networks.
Dated this 25th day of June 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
1. HENRI NOEL FRENAY-OLYFF, of 64 Rue Dailly, Brussels, in the Kingdom
of Belgium, 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 :-
My invention relates to electric telephone systems and has for its object to
simplify the arrangement at the central station and also at the stations of the
subscribers.
In principle the improved arrangement differs from the installations heretofore
used in that the operation of all the apparatus and accessories serving for the
transmission of the call signals and for putting two subscribers in communication is
effected by breaking the circuit, contrary to what takes place in the systems
hitherto employed where these apparatus and accessories are operated by the
closing of the circuit or by sending transient currents through the line.
Now the improved mode of intercalation, with a permanent current, of the parts
for the intercommunication leads to the suppression of a considerable number of
these parts at the station of the subscriber and to a remarkable simplification of the
connections to be established at the central station.
I may recapitulate the various operations to be effected between the subscribers
and the central station which consist in signalling to the central station the call of
a subscriber by disengaging the shutter of an annunciator; in putting the operator
in communication with the subscriber who calls by the introduction of a plug into
the jack and by the operation of a key; in making sure, by means of the test line,
whether the subscriber called is not connected at another table; in connecting this
subscriber then at the table of the operator by the introduction of the second plug
into the corresponding jack and in calling him by switching the call generator into
the line in connecting the two subscribers by the operation of the key which at
the same time puts in circuit the clearing out annunciator by insulating the post
of the operator.
In considering the most complete installations, that is to say, those where the
central station is provided with a multiple switch board I may state that the
essential simplifications which result from the improved arrangements, characterized
by its operation by the breaking of the circuit, consist at the central station in the
suppression of the test line, and at the stations of the subscribers in the suppression
of any current generator or other intermediate devices concerning the call, all the
accessories relative to these functions being transformed in consequence with the
exception of the call generator at the central station and its accessories, and also
the telephone post of the operator, which undergo no changes and operate as in the
systems heretofore used by the closing of the circuit.
I may suppose the employment of communicators jacks to be universally adopted
at the central station, and these apparatus have scarcely to undergo any changes
for the improved system.

page_text: In the first place I will deal with installations without a multiple system for n
single-wire network and then pass on to the multiple systems and "double-wire
networks with or without multiple boards.
In the accompanying drawings
Figure 1 is a diagram of the old arrangement of call annunciators;
Figure 2 represents the arrangement of the call annunciators according to the
present invention.
Figures 1 and 24 are the respective arrangements of the annunciators
themselves.
Figure 3 represents the arrangement of the subscriber's apparatus with an
interruptor.
Figure 4 shows the same apparatus in which the functions of the interruptor are
replaced by the hook of the telephone.
Figures 5 and 6 are two different arrangements of the operating key for the
station.
Figure 6 is a modified arrangement of the key.
Figure 68 is a diagram of the old arrangement with a multiple switch board and
a test line.
Figure 7 represents the now arrangement, the test line being suppressed.
Figure 8 is the arrangement of the plugs and of the cords relative to the latter.
Figure 2 is a diagram of the improved arrangement applied to double-wire
networks.
Figure 4 is the arrangement corresponding to the latter at the subscriber's
apparatus.
Figure 9 represents the arrangement of jacks and plugs for double-wire networks
according to this invention.
Figure 5 represents the arrangement of the cards and their connection with the
operating parts.
Figure 10 is a modification of the jack shown in Figure 9.
Figure 11 represents the prrangement of the jacks for the system with a multiple
switch board of the improved kind with the test line omitted.
Figure 12 shows the connection of the plugs with the parts for the inter-
communication and the operating key and
Figure 13 a diagram of the general arrangement of the system with a multiple
switch board according to this invention.
In the arrangement heretofore used for calling the central station the subscriber
bas at his station a magneto current generator ur battery by which he sends
currents through the line, at the end of which is, at the central station, an
annunciator A connected directly with the earth as at T Figure 1 to disengage the
shutter for exciting the electromagnet which attracts the armuture and raises a
catch (Figure 1^).
In the improved arrangement the current generator is dispensed with at the
subscriber's station and replaced by a source of electricity P (some elements of a
battery) at the central station and common to all the subscribers, this source of
electricity being included between the annuncintors and the earth likewise common
to all the subscribers, (Figure 2). In this system the current obtained from the
central source is permanent and keeps the shutters of all the annuseintors engaged
by the attraction of the armatures whose catches puss through the shutters V
(Figure 2). For disengaging them the circuit must be broken, because then the
armature ceasing to be attracted, the said enich e drops and enables the shutter
which is no longer retained to fall down. This therefore gives rise to but a slight
modification in the annunciators hitherto used, whilst on the other hand I effect a
saving of all the call current generators at the subscribers' stations. The call
devices are replaced at the subscriber's station by a simple interruptor I.
I
The interruptor may be actuated either by a button upon which the subscriber
presses, or also in an automatic manner by unhooking the telephonic.
When use is made of the interruptor I the installation of the station receives the

page_text: arrangement shown in Figure 3. The microphone M with its battery 1, its
induction bobbin and the telephone are arranged at rest as shown in Figure 3.
The line Lin which the receiving bell S is included passes to earth through the
hook C of the telephone and the interruptor I whose button it is sufficient to push
in order to break the circuit and disengage the shutter of the annunciator at the
central station. The receiving bell S operating only under the action of alternating
currents may be inserted into the circuit of the battery at the central station
without inconvenience.
In case the interruptor is suppressed and the circuit is broken automatically.by
the unhooking of the telephone the station is arranged as shown in Figure 4, that
is to say the line circuit will be connected to the bell by the hook itself, the
bell S being then inserted between the latter and the earth.
The call having been transmitted by the subscriber the operator insulates the
line from the call signal and from the earth by introducing one of the plugs of a
pair of intercommunicating cords into the jack corresponding to this subscriber.
He thus puts this subscriber in communication with his apparatus by the operation
of the key which he has for this purpose. Then he introduces the plug of the
second cord into the jack of the subscriber with whom it is desired to communicate
and he calls him by connecting with the line of this subscriber the circuit of the
alternating current generator by pressing a button. Then he insulates his
apparatus by the operation of the key, leaving the two subscribers in communi-
cation; he waits until the clearing out annunciator is actuated, which he has placed
in the circuit of the subscribers by the displacement of the key inserted between
each pair of flexible cords.
According as this key occupies one or the other position there is in the circuit
of the cords either the clearing out annunciator or the microphone of the operator
enabling him to communicate with the subscribers either by speaking to them or
by exciting their receiving bell by connecting the circuit of the alternating current
generator to one or the other line by pressing the corresponding buttons.
When in the arrangement heretofore used the operator displaces the key from
one of these positions to the other the circuit of the clearing out annunciator will
be interrupted which can therefore operate only as long as it is put in circuit by an
operation of the key. In the improved system this interruption must not be able
to take place, because it would have the effect of unduly operating the clearing out
annunciator which is operated in the same manner as the call annunciator, that is
to say by the breaking of the current due to the operation of the subscriber
pressing the interruptor. In this case the old key could not therefore be used and
it must be completed so as to keep the circuit of this annunciator always closed.
This is obtained in a very easy manner by constructing the key W as shown in
Figure 5, that is to say by providing it with two contacts c c a third contact c¹
always connecting the circuit to the battery PI even when the two contacts c
communicate with the operators instruments M' as in Figure 5. while these
contacts connect the circuit of the annunciator A' to the line by the operation of
the key when the operators telephone is put out of circuit as shown in Figure 6.
The key has preferably the form of a sector made of wood or ebonite, adapted to
turn upon its centre o and carrying at its peripheral part the contacts c c c sliding
alternately upon six springs rr, p, r, the first pair corresponding to the call
signal, the second pair to the call buttons band to the cords, and the third-pair
to the operators instruments. G is the call generator and b are the buttons or
contacts which enable call currents to be sent through the flexible cords c² c
through plugs on the lines L, L.
The application of the permanent current arrangement to the multiple system
renders it possible, as already stated, to suppress the test line and to retain no other
connections than those which unite together at all the tables the jacks of the same
subscriber.
In fact the independent test line connecting the body or fixed part of the jacks
was indispensable in the system heretofore used.

page_text: Now in the improved system the call signals are in a closed circuit and there is
no inconvenience in directly connecting the second spring to the body or fixed part
of the jack, and this arrangement considerably simplifies the installation as will be
seen from Figure 7. On the other hand if under these conditions 1 introduce a
plug into the jack the circuit of the subscriber is broken and the call signal would
be disengaged if the circuit could not be connected to other earth than that of the
subscriber. This can be obtained in a very simple manner by the arrangement.
shown in Figure 8. In this figure are the wires connected to the call buttons
and the key of the table and are the flexible cords carrying the plugs b
The plugs and cords have a double circuit and the second of these circuits is
permanently connected to earth. The second circuit of the plug connects the body
or fixed part of the jack, while the first circuit corresponds to the first spring of
the jack and consequently to the subscriber. Therefore even before this circuit to
the annunciator is broken by the raising of the spring it is closed by the body or
fixed part of the jack connected to the second circuit and to the earth common to
these circuits. In this manner the circuit formed by the body or fixed parts and
the connections between their jacks may therefore be broken at will without
inconvenience for the annunciator, and all the wires of the test line of the system
hitherto employed are suppressed.
To make sure whether the circuit has been broken by the introduction of a plug
at any table before giving communication to a subscriber it is sufficient 10 senil
through the said circuit weak alternating currents for example by the aid of a
small magneto machine or small induction coil G' (Figure 7) susceptible of
producing a certain noise in the telephone of the operator when the latter touches
with the extremity of a plug the body or fixed part of one of the jacks of the line,
which noise is heard as long as the circuit is not broken, but which ceases to reach
the ear of the operator as soon as the circuit is broken. Suppose for instance the
communication to be established with the second table (Figure 7) as has been
stated, the body or fixed part and the second strip of the jack are then put to
earth, and the extremity of the plug is in relation with the upper spring of the wire
of the subscriber.
If the operator of table 1 wishes to take this subscriber and if by means of a
plug he touches the body or fixed part of the jack he no longer hears the noise of
the magneto machine. If it is the operator of table 3 he does not hear the noise
either, the body or fixed part being put to earth and the derived current to the
operator much too weak to enable the noise of the magneto machine to be heard.
When therefore the operator hears the noise of the magneto machine through the
jack touched, the subscriber is free, and he is occupied when this noise is no longer
heard.
If in the simple or multiple systems I wish to reduce the number of elements
necessary for the operation of the clearing out annuncintor it is sufficient, instend
of having this annunciator and the battery in series, as in Figures 5, 6, 5 and 12,
to put it in shunt as in Figure 6*.
The annunciator is constructed and regulated for operating by a current of given
intensity, and this intensity is reached in the circuit of the annunciator only at the
moment when the subscribers, having finished speaking interrupt their line and,
thus insulating the second shunt connected to the battery by these lines, cause the
whole current of the battery P to pass through the annunciator.
The application of the system with a permanent circuit to double wire networks
comprises the same simplifications as hereinbefore described, and it may be easily
realized by some insignificant constructive changes to be made in the jacks, plugs
and their connections.
With single-wire networks, the jack has two strips, as shown in the diagram
Figure 2. The only change to be made therein consists in connecting the second
strip to the body or fixed part of the jack by a temporary contact K which at rest
connects the line L' to the bell S and the earth T. If the subscriber, in order to
ring, unhooks the telephone thus moving the switch from the position pl to the

page_text: position he breaks the circuit, the current from the battery P at the central
station ceases to pass through the call signal A and the latter operates. The
extremely simple arrangement at the subscriber's station is represented in
Figure 4. The bell S at this station is then insulated and the apparatus for the
conversation is put in the closed double circuit at the central station by the intro-
duction of the plug which insulates the second strip of the jack by removing it
from the contact K.
The arrangement of the jack is represented in a more complete manner in
Figure 9, which shows the plug introduced three-quarters. The plug in this case
comprises three circuits the first of which is put in connection with the earth.
When the plug is introduced the first contact must take place at a so as to put one
of the strips to earth before it is moved away from K in order to obviate the
operation of the annunciator A. By pushing it then home the second contact n³ of
the plug closes by the strip the circuit through the line L' in the same manner
as it has already closed the same by the third contact L2 through the other line by
the body m or fixed part of the jack.
The manner in which the plug is connected to the operating apparatus is shown
with sufficient clearness in Figure 5A does not require any supplementary
explanation.
Instead of a plug with three circuits use may be made of a plug with two circuits
but in this case a third strip is needed in the jack for the purpose of putting the
annunciator A to earth.
This arrangement is represented in Figure 10. The form of the plug is the
same, but the third strip 13 of the jack permits of the suppression of the circuits n
which it replaces for putting the annunciator to earth, the extremity of the plug
putting the strips previously in circuit.
Then the operations take place as follows: For ringing at the central station the
subscriber unhooks his telephone, interrupting by this operation the circuit at the
central station by introducing the plug into the jack for putting to earth
the annunciator A by its first contact (Figures 9 and 10).
The first strip is put in communication with one line L' and the body or fixed
part of the jack with the line L. The circuit is then closed at the central station
upon the instruments M' of the operator. The subscriber called is rung in the
ordinary manner. By operating the key W (Figure 5) the clearing out
aumanciator A is inserted in shunt upon L and L.
When the conversation is finished it is sufficient for the two subscribers to hang
up the telephone for automatically breaking the circuit and consequently stopping
the operation of A¹.
For the application to the multiple system the jack receives outside the
contact Ka second contact K' corresponding to the strip as shown in Figure 11
while the plug remains exactly as shown in Figure 9. It has thus the effect of
putting to earth by its circuit n' and then putting by the contact K' the strip
in communication with the strip and the body or fixed part m with its circuit.
The connection of the plug with the operating parts are shown in Figure 12.
The microphone induction coil has three circuits, one of which is connected to
the circuits an¹ of the two plugs. This arrangement acts as the test line. When
a subscriber called is not in communication, and the orifice of the jack is touched a
noise is heard in the telephone due to the battery P whose current passes through
the annunciator A, strips, contacts and bodies or fixed parts of the jacks,
through the circuit n' of the plug with which 1 operate and lastly through the
third circuit of the coil B so that a current will be induced in the telephone T. If
on the contrary the subscriber is in communication this circuit is broken and
nothing is heard.
The suppression of the test line is therefore realized by the arrangement in
consequence of the jacks and of their plugs with the same facility and simplicity
for the double wire networks as for single-wire networks.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, 1 declare that what
1 cluim is :-
First. In electric telephone systems, for the purpose of simplifying the same and
suppressing the call generators at the subscribers stations and the test line at the
central station, the arrangement of the connections between the stations of the
subscribers and the various parts at the central station in such a manner that
the operation of the call and clearing out annunciators and the signalling of
occupation of the test shall be caused by breaking the current which traverses them
in a constant manner at rest and emanates from a source of electricity at the
central station.
Second. In single wire network of the kint set forth in the first claim the
intercalation of the call annunciator between the battery or common source at the
central station, connected on the other hand to the earth and the jack connected
through the line of an interruptor at the subscriber's station likewise put th
earth, the shutter of the annunciator being thus maintained by the excitation of
the electromagnet and disengaging by the operation of the interruptor breaking the
circuit (Figure 2), and in certain cazes the replacement of the interruptor by the
hook of the telephone (Figure 4).
Third. In a telephonic network of the kind set forth in the first claim the
employment at the central station of an operating key keeping the circuit of
the nununciator of the end of the conversation closed in all its positions in order to
prevent its untimely disengagement during the operations (Figures 5 and 6).
Fourth. In a single-wire network of the kind set forth in the first claim the
arrangement of the test characterized by simple connection of the first strip of
the jack of one table with the second strip of the jack of the preceding table, and
the connection of the second strip with the fixed part of the jack, and by the
combination with these jacks of a plug with a double circuit, one of which com-
municates with the subscriber while the other sends to earth the current of the
annunciator for preventing its disengagement by interrupting at the same time an
induced current the noise of which is normally perceptible by the operator
ascertaining by this interruption that the subscriber has been given to another
table (Figures 7 and 8).
Fifth. In a network of the kind set forth in the first claim for telephoning by
double wire, a jack with two strips the second of which is independent of the first
and normally closes the circuit of the annunciator hy an intermediate contact K
of the fixed part of the jack (Figure 2) in combination with a plug with three
lines the third of which serves for putting to earth the annunciator before breaking
the contact the other two closing the double-wire circuit by the first
strip and the fixed part of the jack (Figures 9 and 5^), and the modification of this
jack with three strips, one of which is connected with the earth of the annunciator
(Figure 10).
Sixth. In a double-wire network of the kind set forth in the first claim the
arrangement of the test characterized by a jack with three strips, the third of
which comprised between two intermediate contacts K, K' connects at rest the
circuit of the annunciator to the line by the first contact K the second K' serving
to connect the circuit to the earth of the annunciator at the time of the introduction
of the plug by cutting it out of the line, the induced current of the test being
produced by a third circuit of the induction coil at the post of the operator
(Figures 11, 12 and 13).
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.