IMPROVEMENTS IN TELEPHONIC EXCHANGE SYSTEMS AND APPARATUS"
Year: 1882

page_text: LETTERS PATENT to George Lee Anders of Queen Victoria Street in the
City of London for an Invention of "IMPROVEMENTS IN TELEPHONIC
EXCHANGE SYSTEMS AND APPARATUS"
PROVISIONAL SPECIFICATION left by the said George Lee Anders at the
Office of the Commissioners of Patents on the 16th February 1882.
GEORGE LEE ANDERS of Queen Victoria Street in the City of London
" IM-
PROVEMENTS IN TELEPHONIC EXCHANGE SYSTEMS AND APPARATUS."
My Invention relating to improvements in telephonic exchange systems and
apparatus has reference to the construction and arrangement of the telephones
themselves and their batteries and the mode of using the same in telephonic
exchange systems
According to my Invention I combine together a telephonic transmitter of the
type hereinafter referred to a telephonic receiver and a peculiar battery hereinafter
described in a portable case capable of being held in the hand the several apparatus
which form together the compound instrument being arranged normally in the
proper position relatively to each other for action and so that the sound waves
shall act both upon the receiver and transmitter during the operation of
transmitting whereby a louder and clearer articulation is obtained.
The transmitter which I employ is one of the type of what is known as
Hunning's transmitter that is to say, one, the handling of which ensures its
adjustment. I divide the chamber or space for containing the powdered carbon or
finely divided conducting material in a loose and free state into a series of
separate compartments whereby the tendency to a prejudicial accumulation of the
said material in one place when the apparatus is in use is obviated. The
transmitter may be conveniently constructed by the employment of a washer of
felt or other suitable non-conducting material perforated with say three holes, this
washer is attached by an insulating ring to a metal plate secured in the case of the
compound instrument and the holes being filled with the powdered carbon or finely

page_text: divided conducting material in a loose and free state a thin diaphragm composed
wholly or partly of metal is placed over the same and secured at its edges to the
insulating ring by a metal ring and screws. In front of the diaphragm is the
mouth or ear piece of the telephone and in the rear of the metal plate is an electro
magnetic receiver whilst behind the latter is the peculiar battery next hereinafter
described. The battery consists of a plate of carbon covered with a salt of
mercury and of a zinc plate which normally is held out of contact with the
mercurial salt by means of a spring, a push button being provided in order to
bring the two into contact when the apparatus is required for use.
Instead of employing a salt of mercury any other salt may be employed which is
capable of being used in a sufficiently solid condition and which will in this
condition give rise to galvanic action between two dissimilar conducting plates
when brought in contact with it.
The circuit is from line through the battery receiver and transmitter and back to
line. By means of my Invention all the working parts are enclosed in a single
instrument which is self contained and portable and brought within a conveniently
small compass, so as to be capable of being held in the hand.
In some cases I may use a transmitter of the kind herein before described (with a
divided chamber or space for the powdered carbon or finely divided conducting
material in a loose and free state) separate from the battery or from the battery
and receiver.
The transmitter then simply consists of a washer or sheet of felt or other non-
conducting material of any suitable shape perforated with any required number of
holes which are filled with the said powdered carbon or finely divided conducting
material in a loose and free state and of two thin plates composed wholly or partly
of metal arranged one at each side of the felt or equivalent washer and provided
with lugs for the attachment of the terminals and for the facility of attaching the
instrument to a wall or other suitable support.
In order to obtain considerable battery power in a small compass I employ
multiple battery's consisting of a number of elements of the description herein before
referred to combined together so as to be normally kept separate by means of
springs when the battery is not required to be in use but capable of being brought
into action at any time by forcing the elements into contact. When the telephones
are intended for use in telephonic exchange systems and the batteries are not com-
bined with them in one portable self contained instrument as herein before described,
it is desirable in order to reduce to a minimum the number of apparatus at each sub-
scribers office to provide all the requisite battery power at the central station. In
order to enable this arrangement to be practically and efficiently carried out I
employ duplex wires that is to say wires leading from the central station to the
respective subscribers officies and return wires therefrom to the central station and
I provide at the central station a switch-board consisting of a series of pairs of
bars corresponding to the maximum number of pairs of subscribers 'which will
probably require to be in communication at one time with an additional pair for
the central station operator's telephone and also a series of pegs hereinafter
designated compound pegs corresponding to the number of subscribers the said
pegs having duplex contact points connected with the duplex wires the extremities
of each pair of which at the central station form a flexible conducting cord the
arrangement being such that any two subscribers may be placed in communication
by the central station operator inserting the two corresponding pegs in one of the
pairs of bars. I also provide at the central station a battery hereinafter designated
the signal battery with which any subscriber may place himself in circuit by
grounding his apparatus so as to be able to notify to or call the attention of the
central station operator by transmitting an electric pulsation which acts on an
annunciator or visual signal device in combination or not with an alarum or
audible signal device.
I further provide at the central station a series of battery's hereinafter designated
working batteries in number say about equal to one fifth of the total number of

page_text: subscribers according to the maximum number of pairs of subscribers which will
probably require to be in communication at one and the same time any one of
which batteries may be interposed in the circuit of any two subscribers or of a
subscriber and the central station whilst the signal battery is cut out of circuit.
The duplex wires are connected at the subscribers office to an arrangement of
single bell and automatic switch such as are commonly employed in telephonic
exchange systems. For example one of the wires may be connected to one of the
coils of the electro magnet of a signal bell the wire from the other coil of which
is connected to the automatic switch the line then passing to the telephone and
thence to a contact piece with which the switch is normally in contact (when
the telephone is short circuited and out of action) and thence to the return
wire.
From the same wire there is also a branch wire leading to a stop which the
switch touches when allowed to rise by removal of the telephone for use thus
short circuiting the bell and removing it from the working circuit of the
telephones.
A spring is also provided which is connected to earth and is so placed that tho
switch touches it in rising and in falling thereby operating a signal at the central
office.
In one wire of each of the duplex wires at the central station end there is
provided a spring contact for the convenience of inserting when required a key
having a double contact connected with the two polos of one of the working
batteries and beyond the point where this contact is made at the central station
the two wires (suitably insulated) form the flexible cord hereinbefore referred to
which is carried over pulleys and terminates in one of the compound pegs herein-
before described. The other pairs of wires are similarly arranged and connected
cach pair with a separate compound peg. These pegs are normally suspended over
a guide pulley (the flexible cords being maintained taut by pendent weights) and
from one wire of ench of the said flexible cords a branch wire is connected to one
of the coils of the electro magnet of an annunciator drop or visual or audible signal
device the wire from the other coil of the said electro-magnet passing through the
signal battery to earth. The central station operator's telephone may be
permanently connected with one pair of bars appropriated for his use the wire in
which his telephone is situate being provided with spring contacts to admit of the
interposition of a battery key in the circuit when required as hereinbefore
explained. The apparatus operates in the manner next hereinafter described viz :-
Assuming the whole of the parts of the apparatus both at the central station and
subscribers office to be in their normal positions that is to say with the several
pegs of the conducting cords of the duplex wires suspended over their guide
pulleys at the central station and the signal battery in and the working batteries
out of circuit and with the subscribers apparatus out of communication with earth,
if now one of the subscribers desires to communicate with another subscriber
the following series of actions takes place.
The subscriber removes his telephone from the hook of the automatic switch
which rises and by touching the spring grounds his apparatus and thus sends an
electric pulsation which acts upon the annunciator or visual or audible signal
device at the central station.
The attention of the central station operator having been thus called he interposes
one of the working batteries in his wire and also inserts the compound peg corres-
ponding to the said subscribers wire in the same pair of bars as that to which his
own telephone is connected. He then enquires through the telephone the
subscribers wishes and on learning that such subscriber desires to couverse with
another subscriber he places the two subscribers in communication by inserting
their respective compound pegs in one of the free pairs of bars and transferring
the working battery from his own wire to that of either of the subscribers and
replaces the annunciator drops.
The circuit will then be from the working battery at the central office to one

page_text: subscriber back to the central office then to the other subscriber and back to
battery at the central office. The central station telephone is thus cut out and
the two subscribers can converse without the central station operator hearing the
conversation that is taking place.
If another pair of subscribers require to be put into communication at the same
time a similar series of operations takes place another of the working batteries and
a free pair of bars being utilized. When a subscriber has done conversing this
fact is announced automatically at the central station by the subscriber suspending
his telephone on the automatic switch the weight of the telephone causing the
switch to turn on its fulcrum and make a momentary contact with earth and
thereby cause his annunciator drop to fall. The central station operator then
restores the compound pegs and the battery key to their normal position and
replaces the annunciator drops.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said George Leo Anders in the Great Seal Patent Office on the 10th
August 1882.
GEORGE LEE ANDERS of Queen Victoria Street in the City of London
"IMPROVEMENTS IN TELEPHONIC EXCHANGE SYSTEMS AND APPARATUS
23
My said Invention relating to improvements in telephonic exchange systems
and apparatus has reference to the construction and arrangement of the telephones
themselves and their batteries and the mode of using the same in telephonic
exchange systems
According to my said Invention I combine together a telephonic transmitter of
the type hereinafter referred to, a telephonic receiver and a peculiar battery here-
inafter described, in a portable case capable of being held in the hand; the several
apparatus which form together the compound instrument being arranged normally
in the proper position relatively to each other for action, and so that the sound
waves shall act both upon the receiver and transmitter during the operation of
transmitting whereby a louder and clear articulation is obtained.
The transmitter which I employ is one of the type of what is known as
"Hunning's" transmitter that is to say one the handling of which ensures its
adjustment. I divide the chamber or space for containing the powdered carbon or
finely divided conducting material in a loose and free state into a series of separate
compartiments whereby the tendency to a prejudicial accumulation of the said
material in one place when the apparatus is in use is obviated. The transmitter
may be conveniently constructed by the employment of a washer of felt or other
suitable non-conducting material perforated with say three holes, this washer is
attached by an insulating ring to a metal plate secured in the case of the compound
instrument and the holes being filled with the powdered carbon, or finely divided
conducting material in a loose and free state a thin diaphragm composed wholly
or partly of metal is placed over the same and secured at its edges to the insulating
ring by a metal and screws. In front of the diaphragın is the mouth or ear piece of the
telephone and in the rear of the metal plate is an electro magnetic receiver, whilst
behind the latter is the peculiar battery next hereinafter described. The battery
consists of a plate of carbon covered with a salt of mercury, and of a zinc plate which
normally is held out of contact with the mercurial salt, by means of a spring, a push
button being provided in order to bring the two into contact when the apparatus
is required for use. Instead of employing a salt of mercury any other salt may be
employed which is capable of being used in a sufficiently solid condition, and
which will in this condition give rise to galvanic action between two dissimilar
conducting plates when brought in contact with it.
The circuit is from line through the battery, receiver, and transmitter and back
to line. By means of my Invention all the working parts are enclosed in a single
instrument which is self contained, and portable, and brought within a conveniently
small compass, so as to be capable of being held in the hand.
In some cases I may use a transmitter of the kind herein before described (with
a divided chamber or space for the powdered carbon or finely divided conducting
material in a loose and free state) separate from the battery, or from the battery
and receiver. The transmitter then simply consists of a washer or sheet of felt or
other non-conducting material of any suitable shape perforated with any required
number of holes which are filled with the said powdered carbon or finely divided
condneting material in a loose and free state, and of two thin plates composed
wholly or partly of metal arranged one at each side of the felt or equivalent washer

page_text: and provided with lugs for the attachment of the terminals and for the facility of
attaching the instrument to a wall or other suitable support.
In order to obtain a considerable battery power in a small compass I employ
multiple batteries consisting of a number of elements of the description herein before
referred to combined together so as to be normally kept separate by means of
springs when the battery is not required to be in use but capable of being brought
into action at any time by forcing the elements into contact.
When the telephones are intended for use in telephonic exchange systems and
the batteries are not combined with them in one portable self contained instrument
as herein before described it is desirable in order to reduce to a minimum the
number of apparatus at each subscriber's office, to provide all the requisite battery
power at the central station. In order to enable this arrangement to be practically
and efficiently carried out I employ duplex wires that is to say wires leading from
the central station to the respective subscribers' offices and return wires therefrom
to the central station and I provide at the central a switch board consisting of a
series of pairs of bars corresponding to the maximum number of pairs of subscribers
which will probably require to be in communication at one time with an additional
pair for the contral station operator's telephone and also a series of pegs hereinafter
designated "compound" pegs" corresponding to the number of subscribers the said
pegs having duplex contact points connected with the duplex wires, the extremities
of each pair of which at the central station form a flexible conducting cord the
arrangement being such that any two subscribers may be placed in communication
by the central station operator inserting the two corresponding pegs in one of the
pairs of bars. I also provide at the central station a battery hereinafter
designated the "signal battery" with which any subscriber may place himself in
circuit by grounding his apparatus so as to be able to notify to or call the attention
of the central station operator by transmitting an electric pulsation which acts on
an annunciator or visual signal device, in combination or not with an alarum or
audible signal device. I further provide at the central station a series of batteries
hereinafter designated "working batteries" in number say about equal to one fifth
of the total number of subscribers, according the maximum number of pairs of
subscribers which will probably require to be in communication at one and the
same time any one of which batteries may be interposed in the circuit of any two
subscribers or of a subscriber and the central station whilst the signal battery is
cut out of circuit.
The duplex wires are connected at the subscriber's office to an arrangement of
signal bell and automatic switch, such as are commonly employed in telephonic
exchange systems. For example one of the wires may be connected to one of the
coils of the electro magnet of a signal bell, the wire from the other coil of which
is connected to the automatic switch, the line then passing to the telephone and
thence to a contact piece with which the switch is normally in contact (when the
telephone is short circuited and out of action) and thence to the return wire. From
the same wire there is also a branch wire leading to a stop which the switch touches
when allowed to rise by removal of the telephone for use, thus short circuiting the
bell and removing it from the working circuit of the telephone. A spring is also
provided which is connected to earth and is so placed that the switch touches it in
rising, and in falling thereby operating a signal at the central office
In one wire of each of the duplex wires at the central station end there is
provided a spring contact for the convenience of inserting when required a key
having a double contact connected with the two poles of one of the working
batteries and beyond the point where this contact is made at the central station
the two wires (suitably insulated) form the flexible cord hereinbefore referred to,
which is carried over pulleys and terminates in one of the compound pegs herein-
before described. The other pairs of wires are similarly arranged and connected
each pair with a separate compound peg. These pegs are normally suspended over
a guide pulley (the flexible cords being maintained taut by pendant weights) and
from one wire of each of the said flexible cords, a branch wire is connected to one of

page_text: the coils of the electro magnet of an annunciator drop or visual or audible signal
device the wire from the other coil of the said electro magnet passing through
the signal battery to earth. The central station operator's telephone may be
permanently connected with one pair of bars appropriated for his use, the wire in
which his telephone is situate being provided with spring contacts to admit of
the interposition of a battery key in the circuit when required as herein-
before explained. The apparatus operates in the manner next hereinafter
described viz :-
Assuming the whole of the parts of the apparatus both at the central station
and subscriber's offices to be in their normal positions that is to say with the
several pegs of the conducting cords of the duplex wires suspended over their guide
pulleys at the central station, and the signal battery in and the working batteries
out of circuit, and with the subscribers apparatus out of communication with earth,
if now one of the subscribers desires to communicate with another subscriber, the
following series of actions takes place.
The subscriber removes his telephone from the hook of the automatic switch, ·
which rises and by touching the spring grounds his apparatus and thus sends an
electric pulsation which acts upon the annunciator or visual or audible signal
device at the central station. The attention of the central station operator having
been thus called he interposes one of the working batteries in his wire and also
inserts the compound peg corresponding to the said subscribers wire in the same
pair of bars as that to which his own telephone is connected. He then enquires
through his telephone the subscriber's wishes and on learning that 'such subscriber
desires to converse with another subscriber, he places the two subscribers in
communication by inserting their respective compound pegs in one of the free
pairs of bars, and transferring the working battery from his own wire to that of
either of the subscribers and replaces the annunciator drops. The circuit will then
be from the working battery at the central office to one subscriber back to the
central office, then to the other subscriber and back to battery at the central office.
The central station telephone is thus cut out and the two subscribers can converse
without the central station operator hearing the conversation that is taking place.
If another pair of subscribers require to be put into communication at the same
time a similar series of operations takes place, another of the working batteries
and a free pair of bars being utilized. When a subscriber has done conversing
this fact is announced automatically at the central station by the subscriber
suspending his telephone on the automatic switch the weight of the telephone
causing the switch to turn on its fulcrum and make a momentary contact with
earth and thereby cause his annunciator drop to fall. The central station operator
then restores the compound pegs and the battery key to their normal position and
replaces the annunciator drops.
And in order that my said Invention may be perfectly understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several Figures on the accompanying Sheets of Drawings:
Figure 1 (Sheet 1) of the accompanying Drawings represents a longitudinal
vertical section of a combined transmitter, receiver, and battery, constructed and
arranged according to my said Invention. Figure 2 is an end view with the mouth
or ear piece and transmitter diaphragm removed. Figure 3. is an elevation, and
Figure 4. a horizontal section of a transmitter constructed according to a modification
of my said Invention. Figures 5. 6, 7 and 8 illustrate a compound battery
constructed according to my said Invention. Figures 5, and 6, being respectively a
side and end elevation of the battery as seen when out of action, Figure 7 a side
clevation of the same with the elements in position for action and Figure 8, a plan
corresponding to either position.
The same letters of reference indicating corresponding parts in Figures 1, to 8.
inclusive.
Figures 9 to 14 (Sheet 2) illustrate my improvements in the telephonic exchange
avstem itself Figura is a front elevation of a switch board constructed and
.

page_text: arranged according to my said Invention. Figure 10, is a vertical section of the
same taken along the line 1. 2, (Figure 9) and Figure 11, is a vertical section of a
portion of the same, the section being taken along the line 3-4. (Figure 9)
Figure 12 is a view of an apparatus adapted for use in a subscribers office, and
Figures 13, and 14, are diagrams illustrating the arrangement of the circuits and
their connections.
The same letters of reference indicate corresponding parts in Figures 9, to 14,
inclusive.
Referring to Figures 1, and 2 which illustrate a compound instrument having a
telephonic transmitter, telephonic receiver, and battery combined together according
to my said Invention. A is the transmitter, B. is the receiver, and C, is the
battery, arranged the one at the rear of the other and all contained in a case D of
convenient size for handling with a mouth or ear piece E, common to the transmitter
and receiver. The transmitter A, is one of the type of what is known as Hunning's
transmitter that is to say, one the handling of which ensures its adjustment, but I
prefer to construct it in the improved manner next hereinafter described. a is a
washer of felt or other suitable non conducting material perforated with say three
holes at b. b. b.; this washer is attached by an insulating ring c, to a metal plate d,
secured in the case D of the compound instrument, and the holes at b, b, b, are
filled with powdered carbon or finely divided conducting material e, in a loose and
free state, and a thin diaphragm f, composed wholly or partly of metal is placed
over the same and secured at its edges to the insulating ring c, by a metal ring g,
and screws. In front of the diaphragm is the mouth or ear piece E, (before
referred to) of the telephone and in the rear of the metal plate d, is the receiver B,
which may be an ordinary electro magnetic one, while behind the receiver is the
battery C, which is of the peculiar construction next hereinafter described. The
battery consists of a plate h, of carbon supported upon a partition i, of the case D,
and covered with a salt of mercury k, and of a zinc plate l, which normally is held
out of contact with the mercurial salt, by means of a spring m, carried by an
insulating, block n, the latter being secured to the partition i. A push button o,
also of insulating inaterial is provided by the aid of which the zinc plate l, inay be
brought into contact with the mercurial salt k, when the apparatus is required for
use. The circuit is then by the wire 1, from line through the battery, receiver and
transmitter and back to line by wire 2. When the zinc plate l, is brought into
contact with the mercurial salt, electrical conditions are established whereby a 3
current is caused to pass through the apparatus. Although I prefer to use a salt
of mercury as one of the elements of the battery, on account of the well known
action of the metallic mercury deposited in amalgamating the zinc and thus
preventing local action yet, any other salt may be employed which is capable of
being used in a sufficiently solid condition to form a consistency and which will in
this condition give rise to galvanic action between two dissimilar conducting plates
when brought in contact with it. By means of my said Invention, all the working
parts are enclosed in a single instrument which is self contained and portable and
brought within a conveniently small compass so as to be capable of being held in
the hand, while all the said working parts are arranged in the proper position
relatively to each other for action so that when the circuit is completed by bringing
together the two poles of the battery the instrument is ready for use. By dividing
moreover the chamber or space for the powdered carbon, or finely divided conducting
material in a loose and free state, into a series of separate compartments the tendency
to a prejudicial accumulation of the said material in one place when the apparatus
s in use is obviated. A further advantage which attends the use of the compound
instrument is due to the fact that the sound waves are caused to act both upon the
transmitter and receiver during the operation of transmitting whereby a louder
and clearer articulation is obtained
In some cases I may use a transmitter of the kind herein before described (with
a divided chamber or space for the powdered carbon or finely divided conducting
material in a loose and free state) separate from the battery or from the battery

page_text: and receiver. A transmitter adapted for use in this manner is shown in Figures 3
and 4 of the Drawings. It consists of a washer or sheet a, of felt or other non
conducting material of a rectangular shape as represented or of any other suitable
form, perforated with any required number of holes at b, b, b, which are filled with
the said powdered carbon or finely divided conducting material e, in a loose and
free state, and of two thin plates f. f¹. (composed wholly or partly of metal)
arranged one at each side of the felt or equivalent washer and provided with
lugs g¹, g, for the attachment of the terminals 2, 1, and for the facility of attaching
the instrument to a wall or other suitable support.
In order to obtain considerable battery power in a small compass, I employ
multiple batteries constructed and arranged in the manner illustrated in Figures 5.
6,7, and 8 of the Drawings. They consist of a number of elements of the description
herein before referred to, and illustrated in Figure 1, combined together. They
may be conveniently constructed by threading the plates of the several elements on
rods or pillars p, of non-conducting material standing up from a base plate q, the
upper ends of the rods or pillars p, being connected by a cross head carrying a push
button O, likewise of insulating material. Springs m, are provided by means of
which the several zinc plates b, are normally kept separate from the layers k, of
mercurial salt (or other suitable salt) respectively opposite to them, as indicated in
Figures 5 and 6. When however the battery is required for use the elements are
brought into contact as represented in Figure 7, by the act of depressing the push
button O. and electrical conditions are set up whereby a powerful electric current
is obtained.
When the telephones are intended for use in telephonic exchange systems and
the batteries are not combined with them in one portable self contained instrument
as hereinbefore described, it is desirable in order to reduce to a minimum the
number of apparatus at each subscribers office to provide all the requisite battery
power at the central station Figures 9 to 14 illustrate a method of enabling this
arrangement to be practically and efficiently carried out. I employ duplex
wires 1, 2, that is to say wires 1 leading from the central station to the respective
subscribers offices and return wires 2, therefrom to the central station, and I
provide at the central station a switch board A, with appurtenances hereinafter
described by means of which any two subscribers, or the central station operator
and any subscriber may be placed in communication. I also provide at the central
station a battery B designated the "signal battery" with which any subscriber
may place himself in circuit by grounding his apparatus so as to be able to notify
or call the attention of the central station operator. I further provide at the
central station a series of batteries C, C', designated "working batteries." Two
only of these are shown in the Drawings but their number should be about equal
to say one fifth of the total number of subscribers or to the maximum number of
pairs of subscribers which will probably require to be in communication at one and
the same time. Anyone of these batteries may be interposed in the circuit of any
two subscribers or of a subscriber and the central station, while the signal battery
is cut out of circuit.
At the centre of Figure 10 will be seen the ends 1, and 2, of one set of the duplex
wires corresponding to one of the series of subscribers.
In describing the connections I shall confine my attention chiefly to ono set as
it will be understood, that the arrangements of the wires and of their appurtenances
is similar for the whole of the sets with the exception that the terminals are
arranged for convenience in two tiers on the switch board A. The wires 1,-2 are
carried down in the form of a flexible cord, and in one of the wires (the wire 1, in
the example illustrated) is provided a spring contact a, so that a key b, with
double contacts connected with the respective poles of one of the working batteries
(say for example C.) may be inserted and a battery thus interposed in the line.
Beyond the spring contact a, the double stranded cord 1. 2, is continued down
then round a weighted pulley c, and up again over pulleya d, d, to a compound
peg e, having double contacts, the wire 1 passing to one contact and the wire 2, to

page_text: the other contact. In the normal condition of the apparatus all of these compound
pegs are suspended over the pulleys d, One of the compound pegs c, of the upper
tier is shown in this position in Figure 10. From each of the wires 1. of the
duplex line wires 1,-2, a branch wire 3 passes to one coil of the electro-magnet D,
of an ordinary annunciator drop or visual or audible signal device E the wire 4
from the other coil passing through the signal battery B to earth.
The apparatus which may be used at the subscribers office will be presently
described, but it will be understood that assuming the compound pegs e, to be
suspended in their normal position as herein before described, if any subscriber
grounds his apparatus a circuit will be completed (see diagram Figure 13) and an
electric pulsation will be transmitted, and the corresponding annunciator drop or
visual or audible signal device E, operated. I shall now proceed to describe the
manner in which two subscribers may be placed in communication. a¹, a³, are a
series of pairs of horizontal bars corresponding to the estimated maximum number
of pairs of subscribers requiring to be in communication at the same time and to
the number of working batteries, with an additional pair for the central station
operators telephone. The central station operator removes the two compound pegs
of the two subscribers from their respective normal suspended position, and places
them between the two bars a¹, a², of any one of the free pairs of bars so that the
one contact surface of each peg shall be in contact with the bar a¹, and the other
contact surface of each peg shall be in contact with the bar a. He also interposes
one of the working batteries (say C.) in their circuit by inserting the key b, between
the spring contacts a. The circuit is then from working battery C. to one subscriber
back to central station then to the other subscriber and back to battery C. or (inore
minutely indicating its direction) the circuit is from the battery C. to the compound
peg of one subscriber through one bar of the pair of bars to the peg of the other
subscriber, and through one of the duplex wires to that subscriber's station
returning thence through the other wire of the duplex wires back to the peg of the
first subscriber and along the other one of the pair of bars to the peg of the second
subscriber whence it passes along one of the wires of the peg to that subscriber's
station returning therefrom along the other wire to the battery C, thus completing
the circuit.
The arrangement of the circuit and the connections generally will be clearly
understood from the diagram Fig. 14 (the arrows showing the direction of the
current) in conjunction with the other Figures. In a similar manner the central
station operator may place his own telephone in communication with any subscriber,
it is preferred however to have the central station operators telephone permanently
connected with one pair of bars, which should be appropriated, for this special use in
communicating with subscribers.
In order that the mode of working may be rendered perfectly intelligible, I shall
give an example of the series of operations which are necessary in order to put two
given subscribers in communication.
Let it be assumed that 2, wishes to communicate with 29. 2 takes up his
telephone thereby grounding his apparatus and causing the annunciator drop 2. to
fall. The central station operator then removes the compound peg c. of 2. from its
normal suspended position and places it in the pair of bars to which his own
telephone is connected, at the same time interposing one of the free working
batteries in the circuit by inserting its key b, (which normally may be contained
in one of a series of apertures. g.) in his own line.
On enquiring of 2, his wishes and learning that he desires to communicate with 29.
the central station operator inserts the compound pegs e. of 2, and 29. in one of the
free pairs of bars and removes the battery key b, from his own line and inserts it
between the spring contacts, a. of the wires of either 2, or (as shown in the
Drawing) of 29-2, and, 29, are now in circuit and may converse together without
the risk of the central station operator hearing the conversation. The operator
then restores the drops to their normal position, and their simultaneous dropping
again (which is effected automatically in the manner hereinafter described) is the

page_text: signal to disconnect the two subscribers. In a similar manner subscribers 3, and 5,
are also represented in the Drawings as being in communication.
The apparatus which may be conveniently employed at the subscribers offices is
illustrated in Fig. 12. The wire 1 is connected through the coils of the electro-
magnet F, of a signal bell G with the automatic switch H, at h. and thence passes
to the telephone; the wire 2, passes to a contact piece i with which the switch is
Dormally in contact (when the telephone is short circuited and out of action) and
thence to the telephone. When a subscriber has done conversing he suspends his
telephone on the hooked end 6, of the automatic switch H, which causes the said
switch to turn on its fulcrum h, and act upon a spring contact piece 5 (sce
Figure 12) which is connected by a wire f, with earth, a momentary current is
thus sent to the central station, causing the annunciator drop to fall, and indicate
that he has finished conversing. The bell G, is short circuited when the telephone
is in use by means of a branch wire 7, from the wire 1, connected to the stop 8,
which limits the upward motion of the switch H.
The operation will be clearly understood from the description hereinbefore given
without further explanation.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that I do not claim broadly as forming any
part of my present Invention, the use of the peculiar battery C, herein before
described with reference to Figure 1 of the accompanying Drawings, nor the
combination of a telephonic transmitter of the type herein before referred to, with
a telephonic receiver in one and the same case, neither do I claim broadly the
combination of a battery, a transmitter, and a receiver in one and the same case
or receptacle, nor broadly the construction of a transmitter the handling of which
ensure its adjustment, nor do I claim broadly combining together a number of
elements so as to produce a compound battery, nor arranging the whole of the
batteries required for the service of the system at the central station but what I
claim as the Invention secured to me by the hereinbefore in part recited Letters
Patent is :-
1, The combination of a telephonic transmitter and battery of the types herein-
before referred to and a telephonic receiver in a portable case capable of being
held in the hand, the several apparatus which form together a compound self
contained instrument being arranged normally in the proper position relatively to
each other for action, and so that the sound waves shall act both upon the receiver
and transmitter during the operation of transmitting all substantially as herein-
before described.
2. In a telephonic transmitter of the type of what is known as "Hunning's
transmitter" or one the handling of which ensures its adjustment, I claim, dividing
the chamber or space for containing the powdered carbon or finely divided
conducting material in a loose and free state into separate compartments
substantially as and for the purpose hereinbefore described.
3. A telephonic transmitter consisting of a sheet of felt or equivalent non-
conducting substance perforated with holes containing powdered carbon or finely
divided conducting material in a loose and free state and covered on each side
with a thin plate composed wholly or partly of metal to which one of the
terminals is connected substantially as herein before described.
4. The combination in a battery of a series of pairs of elements each pair
consisting of a plate of zinc and of a plate of carbon covered with a layer of a salt
of mercury or other suitable salt as herein set forth, and the whole arranged and
combined together, in such a manner that the several elements shall be normally
maintained separate by incans of springs or resilient contrivances when the battery
is not required for use but shall be capable of being brought into contact by the
application of pressure in order to bring the battery into action substantially as
herein before described.
5. In telephonic exchange systems the employment of duplex wires that is to

page_text: say a wire leading from the central station to each subscriber or distant station,
and a return wire to the central station in combination with a series of working
batteries at the central station anyone of which may be interposed in the circuit of
any two subscribers or distant stations or of any subscriber or distant station and
the central station telephone substantially as herein before described.
6 In telephonic exchange systems the combination of a complete metallic circuit
for telephonic communication between a central station and each of a series of
subscribers offices or distant stations with a ground circuit capable of being
employed by the subscriber or occupant of the distant station for the purpose of
actuating a signal at the central station substantially as herein before described.
7. In a telephonic exchange system in which duplex wires are used for each
subscriber or distant station, the employment at the central station of a switch
board consisting of a series of pairs of bars, compound or double contact pegs in
which the said duplex wires terminate, a signal battery and a series of working
batteries in combination with apparatus in each subscribers office or distant
station, the whole arranged and combined together in such a manner that any
subscriber or occupant of a distant station by grounding his apparatus may notify
the central station (the signal battery being then in circuit) while the central
station operator by inserting the required peg or pegs in one of the pairs of bars,
and interposing one of the working batteries in the circuit may place the central
station and any subscriber or distant station, or any two subscribers or distant
stations in communication substantially as hereinbefore described.
In witness whereof I the said George Lee Anders have hereunto set my hand
and seal this Fifteenth day of June in the year of our Lord One thousand
eight hundred and eighty two.