IMPROVEMENTS IN TELEPHONY
Year: 1884

page_text: I CHARLES LANGDON-DAVIES of 110 Cannon Street London Electrician do
hereby declare the nature of my invention for "IMPROVEMENTS IN TELEPHONY " to
be as follows:-
The object of this invention is the use in telephony of line wires through which
ordinary telegraphic communications are carried on.
In order that the telegraph signal and other currents may not be heard
injuriously in the telephone I connect the telephone with the line by means of an
instrument composed of two or more conductors laid together but insulated from
each other, one of which conductors I attach to the line, and another to the
telephone.
Fine copper wire covered with silk or other insulator may be employed. Two
or more of these, (which may or may not be of the same diameter) are laid
together and are then again covered with silk or other suitable material.
The duplex or multiple wire thus prepared is usually wound upon a bobbin, but
may be made into a flat spiral, or other convenient form.
In applying telephones upon a single line wire I usually place the secondary
coil of the microphone in the line.
I employ two of the duplex or multiple bobbins and I connect them with the
line wire on opposite sides of this secondary coil (or if this is not convenient, then
on opposite sides of a resistance of small dimensions, an ordinary telegraph
instrument answers this purpose). Each bobbin is thus connected with the line by
one only of its wires, and the other end of this wire remains insulated.
The receiving telephone is connected with another wire of each bobbin, and the
other extremities of these wires also remain insulated.
Thus no metallic connection is established between the bobbin of the receiving
telephone and either the line wire or the earth, but the receiving telephone is
connected with insulated wires which are in close proximity to other wires which
are in metallic connection at one end with different points in the line wire.
If triple bobbins be employed, then the third wires are coupled by their ends
Such
and form closed circuit or circuits requiring no external connections.
circuits I find very effective in deadening telegraphic and other foreign sounds in
the telephone. These circuits may often be advantageously closed through a
battery, especially a battery of small internal resistance.

page_text: I also use these triple or multiple bobbins in connecting telephones with
telegraph wires in such manner as that the telephonic communication is carriod
on through or by means of two independent telegraph line wires. This I can do
as follows; to one of the line wires I connect one end of one of the wires of a
triple or multiple bobbin; the other end of this wire is insulated, and as a general
rule the wires in my multiplo bobbins are connected by one end only, excepting in
those cases where they are themselves connected end to end, requiring no external
connections.
The second telegraphic wire is similarly connected to a duplex or multiple
bobbin, and the secondary microphone coil, or other resistance is placed between
the two multiple bobbins, the whole being between the two line wires, thus
rendering it unnecessary to insert any resistance to either line wire.
The receiving telephone is connected with one end of one wire in each of the
bobbins.
I make the same arrangement at each end of the two wires on which I desire to
hold communication, and when I do not use the second telegraphic wire I can
connect to the earth the wires of the multiple bobbins which would have been
connected with the second wire if I had used one.
My multiple bobbins enable me to carry the telephonic effect onward from one
telegraphic wire to another, or from one part of a wire to another part, ns for
instance round a telegraph instrument working in the telegraph line or from
the telegraphic wire into the telephone and that without also carrying on the
telegraphic or other electric current, which remains unaffected. I do this by
attaching one end of one wire of my multiple bobbin to one point and one end
of another wire to the other point of the two points I wish to connect; the
telephonic effect then passes freely but the telegraphic current does not pass the
bobbin at all.
When a telephone is employed upon or by means of double wires, and it is
desired to continue the telephonic transmission to a further distance upon a single
wire only, I do this as follows, I connect with the double wire, two multiple
bobbins with a resistance between them, as previously described. I then take one
end of the wire of one multiple bobbin which would have been connected with the
telephone receiver, and I connect it with the earth, the other end of the wire
being insulated. One end of the wire of the other multiple bobbin which would
have been connected with the telephone I connect with the single line wire. At
the telephone station at the other end of the single line I arrange two multiple
bobbins with the secondary of the microphone coil, being in the line as previously
described; and the line being there connected with the earth.
The same arrangement enables me to connect a telephonic branch line with any
point of a trunk line, and whether the trunk line be composed of a single or
double wire. --
By varying the relative diameters of the wires composing my multiplo wires
I am able to make an important difference in the general tone of the telephonic
voice without altering its own relative modulations. This renders it possible for
ime to send more than one telephonic message at the same time on the same wire,
(simultaneously with the telegraphs) as follows. Supposing that I wish to employ
the same wire for transmitting two telephonic messages simultaneously, I arrange
counterpart telephonic posts A and A' at each end of the first communication, and
other counterpart telephonic posts B and B¹ at each end of the second communi-
cation. The wires in my multiple bobbins A and A¹, are so varied in diameter as
makes a change in the voice which I will call change A, and the wires in multiple
bobbins B and B¹ make another and different change in the voice which I will call
change B. Suppose that voice A on its way to A¹ passes through B, I can arrange
that the additional change made by B shall be such as to obliterate the effect of
voice A on telephone B, which nevertheless continues to report voice, B, while
voice A passing to telephone A¹ is reported there.

page_text: The secondary of the transmitting telephone is connected at one end with a wire
in a multiple bobbin, and the line is connected with the same wire of the same
bobbin at the same end, the other end being insulated. The other end of the
secondary is connected in the same way with one end of a wire in the other
multiple bobbin, in company with the line wire; but the line wire in this case
may be another (or return) wire, another part of the same wire, or an earth wire.
In order to increase the power of the telephone and to diminish the effect in the
telephone, of the telegraphic currents, I construct the primary wire of the micro-
phone coil of duplex or multiple wire connected in such a way as to provide two
or more independent battery circuits each having its own microphone contact or
contacts without necessarily employing more than one microphone diaphragm or
other means of varying the pressure of the contacts; an additional wire or wires
may be formed into a closed circuit not requiring external connections.
The secondary microphone coil I also make of multiple wire, including a wire
which forms a closed circuit, not requiring external connections, and wires having
one end insulated.
If the duplex or multiple wires or bobbins contain wires in addition to those
of which the uses have already been described, as may advantageously be the case,
these wires are connected up into circuits needing no external connections.
By these means and by suitable adjustment of the proportions of the parts, I am
able sufficiently to separate the telephonic impulses from those by which the
telegraphic signals are produced, to sufficiently separate telephonic impulses of
different natures from each other, to vary the nature of these impulses, so that
they may be so separated, and to increase the strength of the telephonic impulses.
These duplex and multiple bobbins are not liable to injury by electric storms.
Dated this 6th day of ducunt 100.1.

page_text: "
I CHARLES LANGDON-DAVIES of 110 Cannon Street London Electrician do
hereby declare the nature of my invention for IMPROVEMENTS IN TELEPHONY
and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
The object of this invention is the use in telephony of line wires through which
ordinary telegraphic communications are carried on.
In order that the telegraph signal and other currents may not be heard
injuriously in the telephone I connect the telephone with the line by means of an
instrument composed of two or more conductors laid together but insulated from
each other, one of which conductors I attach to the line, and another to the
telephone.
Fine copper wire covered with silk or other insulator may be employed. Two
or more of these, (which may or may not be of the same diameter) are laid together
and are then again covered with silk or suitable material.
The duplex or multiple wire thus prepared is usually wound upon a bobbin, but
may be made into a flat spiral, or other convenient form.
I call the instruments thus constructed of my multiple wires, electrophones,
because they permit the passage of electrical sounds but arrest the passage of
electrical currents, or at any rate, of such currents as are capable of actuating
telegraph instruments.
One form of electrophone which I employ consists of a coil of wire, say
No 30 Birmingham wire gauge having two strands and being about 500 yards
long, more or less. One end only of each strand is carried to a terminal, the other
end is insulated.
Figure 1 is a diagram representing the electrophone. a and b are the two wires
insulated from one another and each connected at one end only to a terminal upon
the case frame or support. The two wires although shown at a distance apart, it
will be understood, are after being separately wound with silk to effectually
insulate them, held close together by a winding passing around the two wires.
The strand so obtained may be wound upon a wooden bobbin.
The wires may be connected with the terminals as shown by Figure 1 but usually
the arrangement shown by Figure 2 will be found to give better results.
In Figure 3 various ways are shown of employing this electrophone.
At A it is represented applied as a shunt to the ordinary telegraph instruments
at a telegraph station. It here serves to maintain telephonic continuity of the line
whether the telegraph key be opened or closed.
At B the electrophone is shown applied to connect telephonically two telegraph
line wires which for telegraphic purposes remain separate and independent circuits.
At C two of these electrophones are shown applied to connect a branch for
telephonic purposes with a telegraph line wire.
The electrophone in each case is without effect on the telegraphic use of the
wires but it forms a connection by which telephonic impulses can pass.
The voice sounds are freely received in the telephone and there is but little
disturbance by noise resulting from the use of telegraph instruments on neigh-
bouring wires or even on the same wires.

page_text: For connecting the telephone instruments it is convenient to use a double
electrophone which I make by winding on a bobbin about say 1000 yards of the
two wire strand already described. The middle of the strand is brought out and
divided and the ends are taken to four terminals in the manner indicated at
Figure 4 which illustrates also the way in which the electrophone is used in
connecting the receiving and transmitting telephones. The latter is marked R and
the secondary coil of the former is marked T.
Figure 5 shows another way of employing a double electrophone in connecting
the telephone instruments; it is here employed in conjunction with a single
electrophone. This arrangement is very efficient in cutting off telegraphic noises.
Figure 6 shows another way in which the double electrophone may be used in
connecting telephonic instruments upon a telegraph line.
I sometimes make electrophones with three wire strands. The wires are first
separately silk covered as already described and then they are laid side by side
and enveloped by an additional winding. The strand thus prepared is wound upon
a bobbin to a length say of 500 yards.
Figure 7 shows a three wire electrophone applied in connecting telephonic
instruments. As in the previous instances the electrophone is applied as a shunt
to the ordinary telegraph receiving and transmitting instruments which are not
interfered with.
It is not essential that the telephones should be applied in the vicinity of the
telegraph instruments; the arrangements described may be applied as a shunt to
any sufficient resistance in the telegraph line.
And the shunt may include earth connections and is then available as a branch
telephonic line.
Or wherever shunts are indicated they may, instead of being round one
instrument only, or one wire be round the instruments or other resistances or two
wires, including their earth connections as when it is desired to use a return wire
for the telephone.
Figure 8 shows a double three wire strand electrophone:-two of the three wires
are divided in the middle.
In this arrangement as in Figure 6 the receiving telephone is in metallic
connection by one of its terminals with the line wire, but in no case is the circuit
through the telephone.
Figure 9 shows another way of employing a double three wire strand electro-
phone in connecting telephonic instruments.
Figure 10 is a like arrangement but in this case one of the three wires is
connected into a closed circuit; this is an arrangement which has a marked
beneficial effect in deadening telegraphic noises.
Where all the effect desired is not obtained by the use of one electrophone two
or more can be employed; they can be coupled in parallel arc as in Figure 11 or in
series as in Figure 12.
Another use which I make of the electrophone is illustrated by Figure 13 viz;
to connect a two wire telephone circuit, or a circuit working through a return wire
and without earth connection, to a single wire telephone with return through
earth. In this case two simple electrophones are employed each connected by one
of its terminals with the two wire circuit or either side of a resistance which may
be the telephone instruments.
The single line wire is connected with the other terminal of one electrophone
whilst that of the other electrophone is connected to earth.
By like means a telephonic branch may be connected upon a telegraphic or
telephonic line.
If the duplex or multiple wires or bobbins contain wires in addition to those of
which the uses have already been described, as may advantageously be the case,
these wires are connected up into circuits needing no external connections.
In order to increase the power of the telephone and to diminish the effect in the
telephone, of the telegraphic currents, I construct the primary wire of the micro-

page_text: phone coil of duplex or multiple wire connected in such a way as to provide two
or more independent battery circuits each having its own microphone contact or
contacts without necessarily employing more than one microphone diaphragm or
other means of varying the pressure of the contacts. The secondary microphone
coil I also make of duplex or multiple wire to contribute to the same end and to
separate the telegraph from the telephone.
Figure 14 shows diagrammatically the arrangement of the transmitting telephone.
M represents a multiple contact microphone of well known construction and its
contact blocks are supported by a diaphragm or diaphragms.
D is a bobbin on which are wound together four duplex strands or it might be
eight (or other number) of singlo insulated wires. At one end of the reel each of
these wires is separately connected with a microphone contact at the other end all
the wires are brought together and connected through a battery with the other
microphone terminals. Over the primary wires on the bobbin I wind also a
duplex strand to form the secondary and this I connect in circuit not in the
ordinary way so as to establish metallic continuity but I connect one wire of the
duplex strand on the one side of the bobbin and the other wire of the strand on
the other side of the bobbin. Or on the same hobbin I wind still another wire
and this by its two ends I connect with the receiving telephone.
'
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
(1). The use in telephony on telegraph line wires of the electrophone consisting
of compound strands of wire connected by one extremity only substantially as
described.
(2). The use in telephony on telegraph line wires of two or more insulated wires
wound on the same bobbin or in the same coil or bundle and each connected by
one end only in such manner as to transmit telephonic impulses but to arrest
telegraphic currents substantially as described.
(3). The use of telephones to connect telephonic instruments with telegraph
wires substantially as described.
(4). The use in a telephone transmitter of two or more primary coils coupled
in parallel arc and each with its own microphone connection substantially as
described.
(5). The use in a telephone transmitter of two secondary coils each connected to
the circuit by one extremity only substantially as described.
(G). My improvements in telephony substantially as described.
;