Improvements in or relating to Electric Telephones.
Year: 1897

page_text: Improvements in or relating to Electric Telephones.
1, THOMAS SLOPER, of 11, 12, 14 & 15, Brittox, Devizes, in the County of
Wiltshire, do hereby declare the nature of this invention to be as follows:-
This invention relates to certain improvements in the telephone instruments and
systems described in my earlier Patents No. 13367/91 and No. 10250/95.
66
bell
In carrying out my invention I employ a number of main line wires generally
equal in number to the number of telephone stations & also a return or
wire which is generally used only for signalling or calling purposes.
At each station I employ an instrument consisting of a telephone, a switch for
making contact with the other lines, a switch-hook for automatically making the
connections in the instrument itself, and a bell for calling attention.
The switch may be of any suitable form but I prefer to employ a metal arm
turning upon one end, & so arranged that the other end may easily be turned round
& by so doing be brought into contact with studs or springs in electrical connec-
tion with the respective lines, appertaining to the other stations.
The switch-hook may be permanently connected to the home line (that is the
line appertaining to the station) & so arranged that when the receiver is on
its hook a current entering the home line passes through the bell thus calling
attention.
When the receiver is taken off its hook the home line is disconnected from the
"bell" wire
bell, & has then no electrical connection whatever with the return
or earth."
Two contacts which I will call A & B respectively are arranged near the
switch-hook in such a manner that when the receiver is unhooked these contacts
are brought into electrical connection with each other, & also with the home line
through the switch-hook.
The contacts A & B when connected close the circuit of the microphone & the
primary of the induction coil & at the same time connect the switch, the receiver,
& the secondary of the induction coil with the home line.
The arrangements of the various parts are such that a part of the current from
the battery which supplies the microphone is allowed to pass through a shunt
circuit formed by the home line, the instrument of the other speaking station &
the receiver & secondary coil of the home instrument respectively but this shunt
circuit cannot be formed until the instruments at both stations have their switches
in contact with each others lines & their receivers off the hook.
To call attention it is only necessary to place the switch to the line of the station
desired, ring, & then listen at the receiver.
To answer a call it is only necessary to listen at the receiver & move the switch
round until it happens to come on to the calling line. A loud click is heard in
" line. The
the receiver directly contact is made or broken with the "calling
switch is left on this "clicking " line & communication is complete.
It will be understood that the return "bell" wire or eartn is entirely cut off
i

page_text: & the speaking current passes through the line wires of the "calling" & "called "
stations respectively. This renders cross-talk impossible as it is only the stations
which are thus mutually connected that can talk together.
Any two or more pairs of stations can use the system at one & the same time
without overhearing as each pair have a complete metallic circuit for the time
being.
I do not confine myself to any particular method of obtaining the shunt current
on the lines as there are many ways in which this can be done.
The batteries at each end can be arranged to work in unison so that both supply
a shunt current to the lines but as in each case it passes through the high resist-
ances of the secondary and receiver coils the current is small compared to that
passing through the microphones.
If desired a separate battery or batteries may be employed for the lines other
than those supplying the mircrophones.
I sometimes connect one pole of the battery to the switch-hook, and the other
pole to both the home line & part of the primary circuit of the induction coil. By
this means the battery of the called station may be employed to ring its own bell,
to do which I use a Morse key arranged to disconnect the switch from the
instrument & to connect it with the return or bell wire when the button is pressed.
It will be obvious that many modifications of the arrangements described may
be employed without departing from the spirit of this invention.
Dated this 15th day of September 1897
I, THOMAS SLOPER, of 14, The Brittox, Devizes, in the County of Wiltshire, do
hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to certain improvements in the telephone instruments &
systems described in my earlier Patents No. 13367/91 and No. 10250/95.*
In carrying out my invention I employ a number of main line wires generally
equal to the number of telephone stations and also a return or bell wire which is
generally used only for signalling or calling purposes. At each station I employ
an instrument consisting of a telephone a switch for making contact with the
other lines, a switch hook for automatically making the connections in the instru-
ment itself & à bell for calling attention."
The switch may be of any suitable form but I prefer to employ a metal arm
turning upon one end & so arranged that the other end may easily be turned round
& by so doing be brought into contact with studs or springs in electrical connec
tion with the respective lines appertaining to the other stations.
The switch hook may be permanently connected to the home line (that is the
line appertaining to the station) & so arranged that when the receiver is on
its hook a current entering the home line passes through the bell thus calling
attention.
When the receiver is taken off its hook the home line is disconnected from the
bell & has then no electrical connection whatever with the return bell wire
or "earth."
Two contacts which I will call A & B respectively are arranged near the
switch hook in such a manner that when the reciever is unhooked these contacts
2

page_text: are brought into electrical connection with each other & also with the home line
through the switch hook.
.
The contacts A & B when connected close the circuit of the microphone and the
primary of the induction coil & at the same time connect the switch the receiver,
& the secondary of the induction coil with the home line.
The arrangements of the various parts are such that a part of the current from
the battery which supplies the microphone is allowed to pass through a shunt
circuit formed by the home line, the instrument of the other speaking station and
the receiver & secondary coil of the home instrument respectively but this shunt
circuit cannot be formed until the instruments at both stations have their switches
in contact with each other's lines & their receivers off the hooks.
To call attention it is only necessary to place the switch to the line of the station
desired ring & listen at the receiver.
3
To answer a call it is only necessary to listen at the receiver & move the switch
round until it happens to come on to the calling" line.
A loud click is heard in the receiver directly contact is made or broken with
the calling line the switch is left on this clicking line & communication is.
complete.
"
دو
It will be understood that the return "bell wire" or earth is entirely cut off
& the speaking current passes through the line wires of the "calling & the
called stations respectively.
Any two or more pairs of stations can use the system at one & the same time
without overhearing as each pair have a complete metallic circuit for the time
being.
I do not confine myself to any particular method of obtaining the shunt current
on the lines as there are many ways in which this can be done. The batteries at
each end can be arranged to work in unison so that both supply a shunt current
to the lines but as in each case it passes through the high resistances of the
secondary & receiver coils the current is small compared to that passing through
the microphones.
If desired a separate battery or batteries may be employed for the lines other
than those supplying the microphones & this may be common to all the stations.
I sometimes connect one pole of the battery to the switch hook & the other
pole to both the home line & part of the primary circuit of the induction coil.
By this means the battery of the called station may be employed to ring its
own bell; to do which I use a Morse key arranged to disconnect the switch from
the instrument & to connect it with the return or bell wire when the button is
pressed.
In the accompanying drawings Fig. 1 shows the connections of an instrument
arranged upon my improved system in which
A is a spring which makes contact with the switch hook when the receiver is
unhooked & also with a similar spring B.
C is the switch hook.
D is the spring which makes contact with C when the receiver is hung up.
E is the bell.
F is the receiver.
H is the secondary circuit of the induction coil.
Kis the microphone.
L is the line wire.
M is the Morse key for signalling.
N is one contact of the Morse key.
O is the back contact of the Morse key which is connected to the signalling
line V.
P is the switch for connecting to the lines of the other stations.
R is the primary of the induction coil.
T is the battery.

page_text: The operation is as follows. A person wishing to call a station would place the
switch on the number he desired & press the Morse key M. This would connect
the called line to the signalling wire & as this completes the circuit of the bell &
battery at the called station the bell would ring by a current from its own battery.
After ringing the person at the calling station would listen at his receiver.
Hearing his bell ring the person at the called station would unhook his receiver
& move his switch over the studs connected to the different lines. The calling line
is at once indicated by the "clicking" of the receiver & the switch being left on
this line communication is complete.
Fig. 2 illustrates the circuits when four stations are talking. No. 1 is shown
talking to No. 2 & No. 3 is shown talking to No. 4. It will be noticed that the
batteries at each end have a shunt circuit formed by & through the two speaking
lines & the instruments at the other end. Moreover the two batteries work in
unison that is both send currents in the same direction & at the same time. How-
ever many stations there may be in the system each pair of stations when talking
have separate wires all to themselves & quite disconnected from the signalling wire
thus suppose there are 12 stations then 6 pairs would be able to talk upon separate
& distinct circuits.
:
Having now particularly described & ascertained the nature of my said inven-
tion, & in what manner the said is to be performed I declare that what I
claim is:-
1. In a telephone instrument of the class described the arrangement of the
switch hook circuits & contact parts substantially as & for the purpose described
& illustrated in the accompanying drawings.
2. In a telephone system of the class described the combination & arrangement
of parts substantially as & for the purpose described & illustrated in the accom-
panying drawings.