Year: 1887

page_text: Date of Application, 8th June, 1887
Complete Left, 3rd Mar., 1888
Complete Accepted, 4th May, 1888
Communicated from abroad by EMIL MAURITIUS, of Kreuznach, in the Empire of
Germany, Inventor.
I, WILLIAM PHILLIPS THOMPSON F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors 6, Lord Street, Liverpool in the County of Lancaster and 323 High
Holborn in the County of Middlesex, Civil Engineer, do hereby declare the nature of
this invention to be as follows:-
The following is an exact Copy of the specification as communicated by Emil
Mauritius.
The telephone systems now in use have many disadvantages, of which the following
may be mentioned, namely,
(1) According to the present system the calling and concluding signals do not
differ from each other.
(2) The strength of the call battery is often insufficient, and consequently the
signals are not transmitted with sufficient clearness.
(3) The absence of a certain check to ascertain whether the calls have been
transmitted to their respective places, whereby it is impossible to discover at once
interruptions of communication.
All the telephone circuits are provided when at rest with current from the central
station, either 1st by means of an electro dynamic machine, or 2nd by connecting
cach group of 15 to 20 lines of approximately equal resistance with a common battery.
The connections are arranged so that all the batteries at the central station are placed
with the same pole connected with the earth, and each has its other pole connected to
the corresponding electro magnet of the relay.
When the wires are in the state of rest, the circuits are closed by the coils of the
relay, by the line wires, and by the call bell coils, which are in the telephone
stations.

page_text: The signal shutters are so arranged that they fall off when the current is interrupted.
The relays in the signal box are polarized in the sense of the direction of the line
current.
The arrangement at telephone terminal stations is as follows.-
The line wire is led direct to the body of the switch from the lightning arrester of
the apparatus. The switch is also provided with two contacts which are insulated
from each other, and also from a third contact. The three contacts are placed on
springs. Opposite the two first contacts there is besides, fixed on to the switch lever,
a metal piece insulated from the latter, which metal piece connects the two first
contacts when the receiving instrument of the telephone is hung up.
It should be noticed that the signal battery has the opposite poles to that of the
line battery connected with the earth.
The above described arrangement works in the following way :-
The terminal station wishes to speak to the central office.
The subscriber takes the instrument from the hook or lever. The weight of the
instrument being thus removed, the lever moves, breaking the connection with the
line current, but coming in contact with another (a fourth) contact piece which
re-establishes the connection of the circuit with the telephone. The shutter in the
board at the central office has fallen down. The clerk connects the wire on the
speaking apparatus, and receives the orders of the subscriber. The subscriber's call-
bell remains in the mean time at rest.
The armature of the call bell is resting on the interrupting spring. The said spring
cannot however transmit any of the current as the lever of the switch is lying on the
aforesaid fourth contact, and the zinc pole of the call bell battery is in consequence
insulated.
The central office wishes to speak with the terminal.
The operator plugs the line wire to the speaking apparatus, and thereby interrupts
the line current. At the terminal station the telephone is still hanging on the hook
of the switch. The aforesaid first two contacts are connected by the metal plate,
which is insulated from the switch lever. The said lever also touches the third con-
tact. In consequence of the interruption of the current, the armature of the call bell
falls against the interrupting spring, which as long as the telephone is hanging on the
hook of the switch lever, is intermittently connected by its binding screw and the first
two contacts, with the zinc pole of the call bell battery; and by the armature with
one end of the call bell coils. The other end of the coils is connected with the carbon
pole of the battery, and is besides in electric connection with the earth. The call bell
will continue to ring as long as the telephone is hanging on the hook, and as long as
the line current is interrupted.
This ringing will be heard on the telephone at the central office as a drumming
noise, as a series of induced currents will pass through the telephone at the calling
station from the pole of the now active call bell.
The origin of these currents is attributed to the fact that the end of the coils of the
call bell electro-magnet is on the one hand connected with the carbon pole of the call
bell battery, and on the other hand with the earth.
The sounding current will therefore divide itself at the call bell, one part returning
to the carbon pole of the battery, and the other passing to the earth.
(3) If now two terminal stations are to be connected, the clerk of the central office,
who has received the call of the terminal station in the way described in (1) will con-
nect this station with the second, in the usual manuer. The line current in the electro
magnet of the call bell at the second station is thereby interrupted, and the hell begins
to ring. The induced currents which thereby proceed from the bell take their course
through the relay of the central office (which is polarized in the direction of line
current) without placing it in operation, because the signal batteries of the call bells
of the terminal station have their opposite poles connected with the earth to those of
the line batteries, and through the telephone of the first station, which will sound as
long as the call bell sounds at the first station, that is, until the subscriber at the
second station takes the telephone from the hook for the purpose of speaking, and thus

page_text: stops the call bell. As soon as the communicating parties have ceased speaking, and
the telephones are replaced on their hooks, the call bells at both places begin to ring.
The induced currents which proceed from the bell of the first station (the station
which desired the connection) pass through the coils of the relay at the central office
in an opposite direction to the line current, and are opposed to the poles of the line
current. They will cause therefore the armature of the relay to rattle rapidly, a sign
which lasts until the clerk in the central office again restores the wires to their normal
condition, and thereby puts the call bell and the two terminal stations out of action:
The two call bells and their batteries belonging to them act independently of each
other, not isochronically. The currents do not therefore neutralize each other in the
core of the relays, at least not to any large extent.
The concluding signal is very definite, being visible and audible.
As the ringing of the bells at the terminals, until the connection was broken at the
central station, would be annoying to the users, a simple contrivance such as a pieco
of india-rubber, between the bell and the hammer, or a felt cover on the bell may be
used to muffle the sound.
Referring now to the arrangements of a telephone intermediate station.
Below the switch lever of the said station are applied two auxiliary contacts, which
are separate from each other, but are at times connected by the lever so as to act as
conductors, in the same way as the upper contacts hereinbefore described are connected.
The contacts are all placed on springs. The connection of the lower contacts with the
battery (No. 2) and its call bell, as well as the other wire connections, are arranged
in any convenient manner.
Between the two relay contacts and the battery belonging to the other call
bell (No. 1) is inserted a small cranked switch.
When the crank is placed against that contact of the relay (hereinafter called the
rest contact) which is used when the relay is in a state of rest (that is, when the
apparatus is in its calling position) and when a correspondence is taking place through
the said intermediate station to a station beyond, the call bell (No. 1) of the former
would sound as long as the conversation lasted.
The turning of the switch to working contact with the relay causes the bell to be
inactive during the conversation, but it becomes active again when the subscriber has
finished his conversation. The central office is supposed to be situated on the left side
of the intermediate station. The battery of the call bell (No. 2) is arranged to work
in the same direction as the line current, so that it reinforces the saine, and is so
proportioned, that when the switch, above referred to, is placed in working position,
both the station call bell, and that at the terminal, are silenced. The intermediate
station requires to be provided with a key in the circuit of the line current, only when
more than one intermediate station is included, in the system. The closing signal will
be given by the call bell No. 1 at the intermediate station in the way already described.
In arranging the design for an intermediate station, it has been taken for granted;
that the calling of the station is done in the central office, either through putting in
and pulling out of the "jack" or by means of a call button. The stations correspond
with each other and with the central office in the following manner :-
(1) The central office wishes to speak with an intermediate station, or with a
terminal station.
The operator gives the pre-arranged signal several times in succession by means of
the call button. In consequence of this the corresponding shutter falls down, but is,
however, replaced by the operator. Should the shutter again fall down without the
operator pressing the button, it would indicate that the intermediate or terminal station
had been placed in the transmitting position, and that the user at one of these stations
had taken down the telephone for the purpose of speaking. The lever of the switch
at the intermediate station connects the lower contacts. The armature of the call
bell (No. 2) is attracted by its electro-magnets in consequence of the circuit of its
battery being closed by the coils of the said call bell, and by those of the call bell of
the terminal station. If, however, this circuit is interrupted by displacing the switch
of the terminal station, the, armature of the call bell (No. 2) falls against its inter-

page_text: rupting spring, and the call bell acts as an automatic interrupter. If the user at the
intermediate station wishes to wait for the call of the terminal station, he presses upon
a button placed between battery and call bell (No. 2). The latter is silenced by this
action, whilst the call bell of the terminal station rings.
(2) The intermediate station wishes to speak with the central office.
The user places the apparatus in the transmitting position and takes the telephone
off the switch lever. The remainder of the operation is the same as in the case of a
call being sent from any terminal station.
(3) The intermediate station wishes to speak with the terminal station.
The user connects the apparatus with the terminal station, and thereby closes the
line circuit through the call bell (No. 2) and its battery. The flap of the central office
does not fall down. The call bell at the terminal station comes into action, and induces
the user there to place the apparatus in speaking connection with the intermediate
station.
(4). The terminal station wishes to speak with the intermediate station or with the
central office.
The user takes the telephone by means of the switch lever, and gives the pre-
arranged signal. The remaining manipulations are the same as those described in the
foregoing.
An intermediate station can be so arranged as to belong to any subscriber, and to
be only capable of taking the position for through transmission when the telephone is
hung up, that is, when the lever of the switch touches the upper contacts. The said
intermediate station cannot be put into a position to speak with a station on either
side of it until the crank of a second small switch is placed over the "rest contact
of the relay. The intermediate station cannot therefore interfere with the corre-
spondence of two stations on either side of it without a drumming noise being
heard in the telephone of that station, which it has in an unauthorized manner
disconnected.
Moreover, as any two correspondents can agree upon a pass-word with which to
begin their conversation, and as the wire in the telephone room is enclosed in a cable
made of leaden pipe, it will be seen that telegraphic secrecy can by these means be
sufficiently secured.
In the telephonic arrangements of German towns there exists a custom, according
to which one and the same user is connected by means of one circuit, with two stations,
namely, with the central office and terminal station. By this arrangement the pre-
cautions taken to ensure the secrecy of the correspondence between the various
stations are rendered unnecessary. The intermediate station belonging to this user
being generally established at his counting house, and the terminal station at his
works, the former is most frequently connected with the central office, the latier being
connected only occasionally with the Works. Consequently it seems advisable, under
these circumstances, to arrange the intermediate station in such a manner, that it can,
when its telephone is hung up, be used as a transmitting and connecting station, and
so that the central office can be connected with the terminal station only by request,
or vice versa. By this arrangement, all calling devices for these circuits are super-
seded. According to the arrangements shown, the intermediate station is, like each
terminal station rung up" by the central office, or it is connected with another
terminal station by putting in a plug.
The intermediate statian can converse with the central office, or with another head
or intermediate station without ringing up the corresponding terminal station, but it
can be at once rung up by the latter; or the head station can converse with the corre-
sponding terminal station without the flap falling at the Central Office, as the falling
of the flap would cause the latter office to "ring up" the head station and "stand by
awaiting its instructions.
To communicate with the central office, or with the terminal station it is only
necessary to place a spring switch connected with the circuit in the corresponding
sideways position. To connect the central office, or a station on another circuit with
the terminal station belonging to the home circuit, two spring switches are placed in

page_text: position for through transmission. So long as the conversation is transmitted through
the head or intermediate station, the two call bells of the latter are silent as soon as
the correspondence is over and the connection with the central office is withdrawn,
the call bell of the intermediate station begins to ring and thus induces the latter
station to resume the normal position, that is, to make connection with the central
office. The concluding signal of this switch arrangement is given in the manner
already described by the call bell No. 1 of the intermediate station.
The central office may be relieved to some extent with regard to the work of making
the connections, by an arrangement whereby two intermediate stations, which com-
municate often and for a considerable length of time, are enabled to call each other
without the co-operation of the central office, or allowing the closing signal to appear
at the central office, in order to bring about any further connection. This arrangement
consists in a switch of any suitable design. Suppose that the stations have taken down
the telephone receivers and thereby call each other because the lever touches the lower
contacts. The call signal manifests itself as a drumming noise in the telephone of
the station which is called. The bell at the central station does not ring at the call
transmitted from any of the stations, because the first station has the poles of the
battery reversed.
A switching device at either of the stations, and the lifting of the receiving instru-
ment from the hook, permits on the other hand the end signal to appear at the central
office. In order that the terminals may be called from the central office, a current
interrupter with battery and key is provided in the latter station. The call from the
central office is done by pressing the key. The currents thus produced cause a
drumming noise in the telephone at the station in question. It is not found difficult
to construct the apparatus so that by means of the relays very weak currents may
be utilized.
The advantages of this telephone system in place of the arrangement now existing
in Germany are as follows.
1. The abolition of all bell buttons. The certainty of the call signal being trans-
mitted. The fluctuations of current which are developed in the common battery when
the branch currents are interrupted for the sake of signalling can only take effect on
the closed circuits, and remain therefore without any influence. In each interrupted
circuit the current strength is zero and the signals must in every case appear. The
giving of the call signal by simply taking down the transmitting instrument from the
hook and thus causing the connections to be made at the central office. The con-
tinuance of the call signal till a reply is given.
2. The production of a closing signal differing from the calling signal. The pro-
duction of the closing signal by simply hanging the receiving instrument on the hook.
The continuance of the closing signal at the central office until the connection is
broken.
3. The simultaneous transmission of the signals at all the stations concerned.
4. The possibility of connecting several subscribers through the same circuit, without
endangering the secrecy of the communications.
5. The instantaneous indication of interruptions in the working of the apparatus.
6. The increased power for extension of the telephone system consequent upon the
use of line batteries, and the use of an electro dynamic machine, as a source of current
at the central office.

page_text: COMPLETE SPECIFICATION.
Improvements in Telephone Systems.
A communication from abroad by EMIL MAURITIUS, of Kreuznach, in the Empire
of Germany, Inventor.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E, of the Agency for Foreign
Patent Solicitors, 6, Lord Street, Liverpool, in the County of Lancaster and 323 High
Holborn in the County of Middlesex, Civil 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:-
There are many drawbacks attendant upon the use of the present systems of
telephones, namely:
1. The call and concluding signals do not differ from each other.
2. The strength of the call battery is often insufficient, and consequently the signals
are not given with the requisite certainty.
3. The absence of a reliable controlling system, which will enable the operator to
ascertain whether the signals are being given wherever they should be given, that
is to say, the immediate detection of interruptions in the communications is
impossible.
4. It is impossible to apply several receivers to the same circuit, because with
the construction hitherto used, the secrecy of the telegraph cannot be secured
sufficiently.
The object of this invention is to avoid these drawbacks.
In the drawings,
Figure 1, shows the arrangement of a terminal telephone station.
Figure 2, shows the apparatus of an intermediate telephone station, the parts being
at rest, and in the position required for the through transmission of messages.
Figure 3 shows the position of the apparatus of an intermediate telephone station
when messages are being transmitted therefrom.
Figure 4 shows the general arrangement of the switch apparatus of an intermediate
telephone station.
Figure 5, shows an intermediate station as arranged during the through trans-
mission of a message the telephone hanging in place.
Figure 6, shows the intermediate station in the speaking position to communicate
with the terminal station.
Figure 7, shows the intermediate station apparatus in their position for the through
transmission of messages when a conversation is taking place, between two stations
on either side of it, the bell E ringing throughout the conversations.
Figure 8, shows the arrangement of two stations in the speaking position, connected
with each other for the purpose of giving each other reciprocal calls, either directly
or through the issuing office.
In the above Figures the various parts are represented by the following letters.

page_text: A is the wire to the transmitting office. B is the earth wire. C is the call bell
battery (Signal battery). D and E are call bells. (Wecker). F is the wire to the
terminal station. G is a battery. H is a call button. J is a polarized relay. K is
a call apparatus. L is an automatic contact breaker. Mis the line battery.
The whole of the telephone wires are, in the state of repose, supplied with a current
from the central office as follows :-
:-
1. By means of an electro dynamic machine, or (2) as the circuits are approxi-
mately of the same resistance, each group of 15 to 20 is connected to a common
battery. The connections are so arranged that all the batteries in the central office
communicate with the earth through the same poles whilst the other poles are 'con-
nected to the coils of the corresponding electro magnet of the relay within the flap
or clapper box. Consequently, when the wires are in the state of rest, the circuits
are closed by the coils of the relay, by the line wires and by the call bell coils, which
are in the telephone stations.
The signal flaps are so constructed that when the current is interrupted they
fall down.
The relays in the flap box are polarized in the sense of the direction of the line
current.
The arrangement of the terminal telephone station is as follows:
The line wire is led from the lightning protector of the apparatus directly to the
body of the switch. The latter is provided with two contacts a and b (Figure 1),
which are insulated from each other and from the contact c. The contacts a, b and c
are placed on springs.
Opposite the contacts a and b is a plate of metal m, which is fixed by screws on the
lever N, and being insulated from the latter, serves as a conductor to the contacts a
and b when the telephone is hung up on the hook N'. The connections between the
call bell battery C (consisting of three or four Leclanché elements) and the call bell E
and the various contacts including the interrupting spring fare all clearly shown on
the drawing,
It should be noted that the line batteries and the call bell batteries are connected
by unlike poles to the earth, the connection between the latter battery and the earth
being made by means of the binding screw h.
The method of working the above described arrangement is as follows :-
(1.) The terminal station wishes to speak with the central office :
The user takes the telephone from the hook N', interrupts thereby the line current
and effects the connection of the circuit with the telephone through the lever N and
contact d. The flap at the central office falls down. The operator at that office
connects the speaking apparatus with the line wire and receives the instructions of
the user.
The call bell of the user is, during this operation, at rest.
The armature of the call bell is now resting on the interrupting spring f. The
said spring cannot, however, transmit any of the current as the lever N of the switch
is lying on the contact d and the zinc pole of the call bell battery C is in consequence
insulated at a.
(2.) The central office wishes to speak with the terminal station: The operator
plugs the line wire to the speaking apparatus, and thereby interrupts the line current.
At the terminal station the telephone is still hanging on the hook N' of the switch.
Contacts a and b are connected by the metal plate m, which is insulated from the
lever N. The lever touches contact c. In consequence of the interruption of the
current, the armature of the call bell falls against the interrupting spring f, which,
as long as the telephone is hanging on the hook, is intermittently connected by the
binding screw e and contacts and a with the zine pole of the call bell battery C, and
by the armature with one end g of the call bell coils. The other end of the coils is
connected with the carbon pole of the battery, and is besides, in electric connection
with the earth. The call bell will continue to ring as long as the telephone is hanging
on the book, and as long as the line current is interrupted.
This ringing of the call bell will also be audible at the telephone of the central

page_text: office as a sort of drumming noise, in consequence of a series of lesser currents finding
their way from the binding screw g of the call bell, which is in action, and through
the telephone of the calling station. The origin of these lesser currents is attributed
to the fact that the end of the coils of the call bell electro magnet is on the one hand
connected with the carbon pole of the battery C, and on the other hand with the
earth. The call bell current divides itself at the binding screw g of the bell, one part
returns over the call bell coils, and the binding screw to the carbon pole of the
battery, the other part starting from binding screw g, passes through the contact e
into the line wire, and after traversing the coils of the central office, telephone, goes
into the earth.
3). When two terminal stations are to be connected together, the operator at the
central office having received the instructions of the user at the first station, in the
manner described in paragraph (1) connects this station with the second station by
means of a circuit plug. By means of this, the line current in the call bell coils of
the second station will be interrupted, and this call bell begins to ring. The lesser
currents which emanate from the call bell of the second station, find their way
through the relay of the transmitting office, (which is polarized in the sense of the
direction of the line current)-without, however putting the said relay into operation
in consequence of the call bell batteries belonging to the call bells of the terminal
stations, and the line batteries being connected with the earth through unlike poles,
and through the telephone of the first station, which will make a drumming noise as
long as the call bell of the second station is in action, that is to say, until the user
at the second station takes the telephone from the hook for the purpose of conversing,
and thereby causes his call bell to cease ringing. As soon as the conversation of the
communicating parties is finished and the telephones are hung up again on their
hooks, the call bells of both stations ring. Lesser currents proceed in consequence
of this from the call bell of the first station (that which had requested the connection)
and pass through the coils of the relay of the central office in a direction opposite to
that of the line current. The said currents act consequently in the same sense as the
line current, and polarize the core of the relay, causing the armature of the latter to
produce a lively hammering sound as a concluding signal. This signal lasts until
the operator in the central office again puts the two branch circuits, that have been
used, in normal connection, and through this operation the call bell batteries at the
terminal stations are silenced. The fact that the call bell batteries at the terminal
stations are connected with the earth through the same pole, has no appreciable
influence on the character and duration of the concluding signal. Both the call bells
and the batteries belonging thereto work independently of each other and not
isochronically. In consequence of this the currents only neutralize each other to
a very slight extent, this is especially the case when the core of the relay is in
action.
The concluding signal is definite, visible, and audible.
As the ringing of the call bells at the terminal stations (which lasts until the
connection with the central office is broken) might annoy the users, the noise can be
deadened by inserting a disc of india rubber between the hammer and the gong, or
by laying a ring of felt on the latter.
In the arrangements shown in Figures 2 and 3 the closed circuit connection for an
intermediate telephone station may be seen.
Below the switch lever M' of the said station are applied two auxiliary contacts a³
and ², which are separate from each other but are at times connected by the lever,
so as to act as conductors in the same way as the upper contacts a¹¹ are connected.
The contacts are all placed on springs. The connection of the lower contacts a² b³
with the battery G belonging to call bell D, as well as the other wire connections,
can be seen in the drawing.
The connections are made by means of the spring contacts, 1, 2, 3, 4, 5, and 6
(Figure 2) and the spring switch U. The spring switch U being in the upright
position, the line current from the central office enters the said switch partly through
the relay J and contact 1, and partly through the contact 4, and passes out along the

page_text: wire F by means of the contact 2. The line current being interrupted by an office
desiring to correspond, the armature of the relay J rises against the contact i¹ and
completes the circuit of the call bell E through ', a', R, R², i², h, g, fand e, thus
causing the call bell to ring. The lesser currents proceed from the binding screw g,
through c, M', 5, U, 4 and A to the office which caused the interruption of the
current, and pass through the telephone thereof into the earth, returning through B
and h to g.
Suppose the spring switch U to be turned to the left as shown in dotted lines, the
line circuit being closed. The line current now passes through A, J, 1, U. 5, M¹, c, g, h
and B, and into the earth, thus keeping the call bell E silent. The call bell at the
terminal office, which would otherwise ring in consequence of the interruption of the
current in F, is kept silent by the battery G, whose current flows through H, 3, U, 2,
and F. to the terminal station. It there passes through A, N, c, g, h, and B into tho
earth and back again through B at the intermediate station and into the battery G.
When the current in A is interrupted, the bell E rings as before. The telephone
being taken down the circuit of battery C is broken at 6', and the telephone circuit
closed at d.
The contact between U and
Suppose the spring switch to be turned to the right and the line circuit closed.
being broken, the current no longer passes round the
coils of bell E, and the telephone is also cut out of the circuit. As soon as the main
current is broken, contact is made at and the bell E rings. This is instantly
silenced by placing the crank switch R over the contact R¹. The bell E again rings
as soon as the main circuit is closed and contact made at i².
Between the two relay contacts and 2 and the battery belonging to the call bell E,
is inserted a small crank switch R.
When the crank is placed against that contact R2 (hereinafter called the "rest"
contact) which is used when the relay is in a state of rest (that is, when the apparatus
is in its calling position) and when a correspondence is taking place through the said
intermediate station to a station beyond, the call bell E of the former, would sound
as long as the conversation lasted.
By turning the crank against the "working" contact R¹ the relay causes the call
bell to be silent throughout the duration of the conversation, and to sound again as
soon as the latter is over. On the drawing it is supposed that the central office is on
the left hand of the intermediate station.
The battery of call bell D is arranged to work in the same direction as the line
current. The intermediate station having taken the position of a terminal station,
the battery D strengthens the line current, and is so connected and proportioned
that being placed to the left (towards the station to which the message is being
transmitted) it keeps both its own call bells and those of the terminal station silent.
The intermediate station has only to be provided with a key which is inserted in
the line circuit when more than one intermediate stations are placed in the said
circuit.
The concluding signal is given by the bell E of the intermediate station in the
manner already described.
In designing the shunt arrangement of an intermediate station, it is supposed that
at the central office, the "ringing up" of the stations is done by taking the afore-
mentioned circuit plug out, and putting it back several times in succession, or by
means of a call button fixed above the corresponding number of the wire in the flap
box. The manner in which intermediate stations communicate with each other, or
with the central office, is as follows:
.
1. The central office wishes to speak with an intermediate station, or with the
terminal station.
The operator gives the pre-arranged signal several times in succession by means of
the call button. In consequence of this the corresponding flap falls down, but is,
however, replaced by the operator. Should the flap again fall down without the
operator pressing the button, it would indicate that the intermediate or terminal
station had been placed in the transmitting position, and that the user at one of these
B

page_text: stations had taken down the telephone for the purpose of speaking. The lever of the
switch at the intermediate station connects the lower contacts. The armature of the
call bell D is attracted by its electro-magnets in consequence of the circuit of
the battery G, being closed by the coils of the said call bell, and by those of the
call bell of the terminal station. If, however, this circuit is interrupted by displacing
the switch N from the contact c of the terminal station, the armature of the call
bell D falls against the interrupting spring f, and the call bell acts as an automatic
interrupter. If the user at the intermediate station wishes to give the signal "wait"
to the terminal station, he presses upon a button H placed between battery G and
call bell D. The latter is silenced by this action, whilst the call bell of the terminal
station rings.
2. The intermediate station wishes to speak with the Central Office.
The user places the apparatus in the transmitting position and takes the telephone
off the switch lever. The remainder of the operation is the same as in the case of a
call being sent from any terminal station.
3. The intermediate station wishes to speak with the terminal station.
The user connects the apparatus with the terminal station, and thereby closes the
line circuit through the call bell D and battery G. The flap of the central office does
not fall down. The call bell at the terminal station comes into action and induces
the user there to place the apparatus in speaking connection with the intermediate
station.
4. The terminal station wishes to speak with the intermediate station, or with the
central office.
The user takes the telephone and, by means of the switch lever, gives the
prearranged signal. The remaining manipulations are the same as those described in
the foregoing.
The arrangement shown in Figure 4 is that of an intermediate station belonging
to any subscriber, and only capable of taking the position for through transmission
when the telephone is hung up, that is, when the lever of the switch touches the
upper contacts. The said intermediate station cannot be put into a position to speak
with a station on either side of it until the small switch u is turned to the left as
shown in dotted lines. The intermediate station cannot therefore interfere with the
correspondence of two stations on either side of it, without a drumming noise being
heard in the telephone of that station, which it has in an unauthorized manner
disconnected.
Moreover, as any two correspondents can agree upon a pass word with which to
begin their conversation, and as the wire in the telephone room is enclosed in a cable
made of leaden pipe, it will be seen that telegraphic secrecy can, by these means, be
sufficiently secured.
In the telephonic arrangements of German towns there exists a custom, according
to which one and the same user is connected by means of one circuit, with two
stations, namely, with the central office and terminal station. By this arrangement,
the precautions taken to insure the secrecy of the correspondence between the various
stations are rendered unnecessary. The intermediate station belonging to this user.
being generally established at his counting house and the terminal station at, his
works, the former is most frequently connected with the central office the latter being
connected only occasionally with the works. Consequently it seems advisable, under..
these, circumstances, to arrange the intermediate station in such a manner, that it can,
when its telephone is hung up, be used as a transmitting and connecting station, and
so that the central office can be connected with the terminal station only by request
or vice versa. By this arrangement, which is shown in Figures 5 and 7, all calling.
devices for these circuits are superseded. According to the arrangements shown, the
intermediate station is, like each terminal station, "rung up" by the Central Office or
it is connected with another terminal station by putting in a plug.
The intermediate station can converse with the central office or with another head
or intermediate station without ringing up the corresponding terminal station, but it..
can be at once rung up by the latter; or the head station can converse with,the,

page_text: corresponding terminal station without the flap falling at the central office, as the
falling of the flap would cause the latter office to ring up the head station and
"stand by" awaiting its instructions. To communicate with the central office or
with the terminal station it is only necessary to place spring switch ¹ in the
corresponding sideways position. To connect the central office, or a station on
another circuit, with the terminal station belonging to the home circuit, both the
spring switches U₁ and U are placed in position for through transmission. So long
as the conversation is transmitted through the head or intermediate station, the two
call bells of the latter are silent as soon as the correspondence is over, and the
connection with the central office is withdrawn, the call bell of the intermediate
station begins to ring, and thus induces the latter station to resume the normal
position, that is, to make connection with the central office. The concluding signal
of this switch arrangement is given in the manner already described by the call bell
of the intermediate station.
Figure 8 represents an arrangement by which the central office, that is to say, the
connections therewith, are somewhat simplified. It consists in this, two stations
which are frequently and for some length of time connected with each other, are to
be left in a connected state. For this purpose a device is applied to these stations,
which enables them to call each other without affecting the central office, or without
causing the concluding signal to be heard at that office, so that it may establish a
connection with another place. This contrivance consists in a commutator of any
description.
For the sake of clearness a plug commutator P has been shown on the drawings.
The stations having taken off their telephones, call each other reciprocally by lifting
their switch levers against the upper contacts. The calling signal is apparent at the
station, which is being rung up, by a drumming noise in the telephone thereof. Tho
relay of the central office is silent when the call signals are proceeding from either
station, because the calling station, whose lesser currents would, when the batteries
are in normal connection, cause the armature of the relay to strike, has reversed the
poles of its battery. On the contrary the changing of the plug to one or other of
its positions on the commutator, and the lifting of the switch lever, causes the
concluding signals to be given at the central office.
In order that the stations may be rung up from the central office, the latter is
provided with a current interrupter, having a battery and key. The ringing up of
the stations by the central office is (when connection is established therewith)
accomplished by pressing on the key. The lesser currents, which proceed from the
current interrupter, enter the telephone of the station, which is being rung up, and
these produce a drumming noise. In conclusion a remark may be permitted respecting
the production of the concluding signal.
The call bell battery acts, in the above described arrangement, as a working
current battery in two circuits. One circuit is formed by the coils of the call bells.
belonging thereto, and in this circuit the current is self-interrupting. The other
circuit is formed, on the termination of a correspondence between two stations, by
the line wires, the coils of the relay at the central office and the call bell coils at the
second station. In this second circuit the working effect of the current is increased
by a rapid succession of separate current impulses. The increased effect due to these
impulses is so great that the lesser currents (issuing for example, from a call bell
operated by four Meidinger elements) cause the armature of an ordinary Morse
apparatus to rattle slightly.
This action is similar to that which occurs in a swing, to which a large amount of
oscillation may be imparted by feeble impulses constantly repeated. Therefore it
would not be difficult for electricians after due consideration of the amount of
resistance of the two circuits, to arrange the apparatus, call bells and relay in such a
manner that very feeble currents could be employed to work the latter.
By a suitable arrangement of this kind the induction, which is always prejudicial
to the clearness of telephonic messages, can be most effectually remedied.
The hereinbefore described system for telephones, which are connected by line

page_text: wires traversed constantly by a current, possesses the following essential advantages
not to be found in arrangements at present in use in Germany.
1. The superseding of all keys and all oral signals. The certain appearance of
the calling signals. The variations of current, which take place in the common
battery, by the interruption of the various branch circuits (for the purpose of giving
signals), can only act on the closed circuits, and consequently have no injurious
influence. In each interrupted circuit the force of the current is mil, and the signals
must appear in every case. The call signal is produced by simply taking the telephone
off the hook, or by inserting the plug at the central office. The call is continuous
until an answer is given thereto.
2. The production of a concluding signal differing from the call signal. The
cessation of the concluding signal by simply hanging the telephone on its hook, and
the automatic reproduction of this signal by the bells of the telephone stations. The
concluding signal at the central office lasts as long as the telephone station is allowed
to remain in connection therewith.
3. The simultaneous appearance of the signals at all the stations interested in the
correspondence, and the consequent constant control from place to place:
4. The possibility of connecting several users by means of the same circuit
without, at the same time, endangering the secrecy of the correspondence.
5. The immediate detection of break downs, as well as the resultant safety in the
working of the apparatus.
6. The greater possibility of extending the telephonic system in consequence of
the use of line batteries common to a number of circuits, and the use of an electro-
dynamic machine at the central office as a means of obtaining the electric current.
Having now particularly described and ascertained the nature of the said
invention, 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:
In a telephone system worked upon the closed system (Ruhestromverbindung), the
connecting of each of the call bell batteries in such a manner, that the wire from
one pole thereof leads to a contact device, which becomes closed on interrupting the
closed circuit of the line battery, whilst the wire from the other pole leads to a
contact device, which remains closed as long as the telephone hangs on the switch
lever the effect of the joint working of these contact devices being, that the call
bell apparatus at the telephone station can only work properly when the closed circuit
of the line battery is interrupted, and the last named contact is closed.
Dated this 2nd day of March 1888.
WM. P. THOMPSON &.Co.,
Agents for the Applicant.