IMPROVEMENTS IN TELEGRAPHY
Year: 1885

page_text: I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex Patent Agent do hereby declare the nature of this invention for
"IMPROVEMENTS IN TELEGRAPHY" a communication to me from abroad by
Thomas Alva Edison of Menlo Park in the County of Middlesex and State of
New Jersey, United States of America Inventor to be as follows:-
.
The object of this invention is to increase the capacity of telegraph lines in a
simple and practical manner, by the production of instruments and connections
permitting the transmission of two sets of Morse signals back and forth over the
line at the same time without interfering one with the other, and not only between
terminal offices, but between a terminal office and any intermediate office, or
between intermediate offices alone.
The invention is especially applicable to local lines, or to lines having several
offices upon them, to which it can be applied at small expense, each office upon the
line being provided with instruments for transmitting and receiving a second set
of signals and with devices for making the two sets of signals independent and for
insuring against their interference.
Not only is the capacity of the telegraph lines doubled, but the delays occasioned
on lines with several offices, by the interfering of two or more operators in their
attempts to gain possession of the line, are diminished.
A line is employed as usual grounded at its ends and having the ordinary main
battery. Each office (both terminal and way) has a set of Morse instruments,
composed of a key, and a relay controlling circuit of a sounder and local battery.
With these ordinary Morse instruments telegraphing is carried on by Morse
signals in the usual way.
•
At each office is a device working independent of the main battery and acting
to induce in the line impulses of high tension.
This device is composed of an induction coil, the secondary circuit of which may
be located directly in line. The primary circuit of this coil includes a battery and
a back point key. Or in place of this key a back point sounder worked by a key
and local battery may be used.

page_text: The ordinary Morse key is shunted by a condenser so that the line will be
always closed for the induced currents. This condenser also preferably shunts the
relay for a purpose that will be presently set forth. To receive these induced
currents there is provided at each office, a diaphragm sounder which is preferably
constructed upon the principle of the electro-motograph, a diaphragm being kept.
under tension by a spring held by friction upon a revolving chalk cylinder. The
chalk cylinder is rotated continually by a motor electric or mechanical, and the
circuit is closed through the spring and cylinder. This construction of instrument
is a well known telephone receiver and hence does not require further description
here. For the diaphragm sounder a magneto electric telephone or other form of
telephone receiver may be used. The diaphragm sounder at each office is pre-
ferably located in circuit with a condenser and this circuit is preferably a shunt
around a resistance located in the line which resistance is preferably formed by the
coils of an electro-magnet.
The circuit at each office, including diaphragm sounder and condenser, instead of
being a shunt around a magnet in line may be a grounded earth connection or
"leak to earth" and the secondary circuit of the induction coil instead of being
directly in line may be in a condenser circuit whether that circuit is a shunt around
a magnet in line or a "leak to earth.
By the manipulation of the back point keys (or the working of the back point
sounders) signals are thrown upon the line in the form of momentary and sharply
defined waves, which are responded to only by the diaphragm sounders the regular
Morse relays not acting quick enough to respond to these waves.
The regular Morse keys being shunted by condensers, the line is always closed to
the high tension induced currents, and since' such condensers have what is equi-
valent to a low resistance on the instant of closing circuit, it will be seen that a free
path is always provided for the momentary impulses of induction. By extending
these condenser shunts to include the relays as well as the keys, a desirable result
is obtained, in that the counter electro-motive force set up by the relay magnet
effectively stops the passage of the induced impulses by way of the key and relay
and makes the condenser circuit practically the only one closed to these impulses.
The effect of this action is to make the induction circuit of practically the same
resistance whether the regular Morse keys are open or closed.
t
An additional advantage flows from the fact that the induced impulses are not
absorbed by the relays, and the induction signals are made more distinct for that
reason. The condenser shunts are however practically open circuits for the quantity
currents used to operate the relays for the regular Morse signals, the condensers
becoming fully charged and of very high resistance in less time than is required for
the relays to act.
By locating the diaphragm sounders in the circuit of condensers, such sounders
are not affected to the extent of a disturbance of signals by the regular line quantity
currents.
To obtain this result, however even with the diaphragm sounders in condenser
circuits, it has been found that the capacity of the condensers must be definitely
fixed. It has been ascertained that the loudness of sound in the diaphragm
sounder is within certain limits quite independent of the capacity of the condenser
in direct circuit with it, while the disturbing effect of the regular Morse signals in
the diaphragm sounder increases with the capacity of such condenser. Hence the
capacity of that condenser is reduced below the point of disturbance by the regular
Morse signals.
On the other hand, it has been found that the disturbing effect of the regular
Morse signals on the diaphragm sounders 'is diminished as the capacity of the
condenser around the key and relay is increased. Hence these condensers are made
of large capacity say several microfarads each, while the condensers, in direct circuit
with the diaphragm sounders, have a small capacity say a fractional part of a
microfarad each.

page_text: When each diaphragm sounder and its condenser are located in a shunt around a
resistance in the form of a magnet in line the reverse action of the condenser and
magnet will make the condenser shunt the only path practically closed to the
induced currents and the line the only path closed to the regular quantity line
currents as before explained with respect to the relation of the Morse relays and
the condensers shunting them.
The induced impulses thrown by the induction coil upon the line are produced
by a source of energy (the local battery in its primary) independent of the main
battery. These impulses are practically the same whether the regular Morse keys
are opened or closed. By arranging the operating key so that the down stroke will
open the primary circuit and the up stroke will close that circuit, the signal for
the down stroke of the key will be louder than for the up stroke, since when the
primary circuit is closed it absorbs to a certain extent the induction and the impulse
in secondary is weaker than when the primary is opened.
The back point sounder worked by key and local battery, operates the same way.
This difference in the down and up strokes of key is an important one since if the
two signals required to mark the interval of time denoting a dot or dash were the
same the receiving operator might be frequently confused by mistaking the last
signal of a dot or dash for the first signal of the next succeeding dot or dash and
get what is called in telegrapher's parlance the "back stroke."
The instruments and devices described make a complete system of Morse
telegraphy whereby over one line may be transmitted back and forth two sets
of Morse signals, produced by different sources of energy independent of each
other as to loudness and also as to interference in the receiving instruments.
The Invention also embraces further modifications of these instruments and
devices, such modifications relating more particularly to a peculiar transmitter for
producing the momentary and sharply defined waves to which the diaphragm
sounder responds, and also to the manner of connecting the diaphragm sounder to
the line. This transmitter is an instrument constructed to make and break circuit
with great rapidity so as to send for each signal a large number of such momentary
and sharply defined waves.
It may be constructed in a variety of ways.
The form preferred is a rapidly revolving circuit controller kept in motion by a
suitable electrical or mechanical motor.
This circuit controller may be placed directly in line, but it is preferred to place it
in the primary circuit of an induction coil, the secondary circuit of which is directly
in the line, or is in a condenser circuit connected with the line. This condenser
circuit may be a ground connection from line, or a shunt around a resistance or
magnet in line. In the primary circuit of the induction coil is a battery and in a
shunt around the revolving circuit controller is a sounder. with both its front and
back points connected in circuit and operated by a key and local battery. In place
of a sounder a key may be employed connected to close circuit at front and back
points.
Normally the sounder or key closes this shunt at its back contact and the
revolution of the circuit controller does not affect the induction coil. The
movement of the sounder lever (or the key) first breaks this shunt at its back
point and then closes it at its front point During this interval while the shunt
circuit is open, the circuit controller produces a series of waves in the primary of
the induction coil and the secondary of such coil throws upon the line a large
number of momentary and sharply defined waves. The return movement of the
sounder lever or the key first opens and then closes the shunt circuit producing the
same result as in its forward movement.
The momentary and sharply defined waves do not work the relays, but are
responded to by the diaphragm sounders and are translated by them into sound
the intervals between the signals representing dots and dashes. The number of
waves transmitted for each signal is sufficiently great to make a corresponding
number of air waves audible and hence the sound is transmitted electrically instead

page_text: of being produced by a mechanical blow which is the result of a single electrical
impulse, (as at an ordinary Morse sounder).
To make the signal different for the down and up strokes of key, the lever of
the working sounder controlling shunt around circuit breaker is connected with a
dash pot, the plunger of which has a valve opening in one direction so that the
sounder lever will have a quicker movement in one direction than the other.
This movement is preferably made quicker on the up stroke of key causing the
second signal marking the interval denoting a dot or dash to be weaker or
shorter or of different tone from the first signal. This prevents confusion in
receiving.
Instead of a dash pot with valved plunger for varying alternate signals a device
can be used consisting of a retarding fan secured to a spindle with ratchet wheel.
A cog wheel loose on the same spindle has a pawl which engages with said ratchet
wheel. The sounder lever has on its end a toothed sector engaging with said cog
wheel. The movement of the sounder lever in one direction will turn the fan; in
the other direction the cog wheel turns free of the ratchet wheel.
At
As a modification of the Transmitter I may employ the following equivalent
arrangement, videlicet:-A magnet worked by a key and local battery operates a
lever which is extended the required distance to get the necessary movement.
its end the lever carries a finger. playing over the surface of a contact block.
This contact block has its face composed of a large number (preferably fifty or
more) of thin plates separated by insulation. This contact block and the lever are
connected in circuit preferably in the primary of an induction coil, and the
movement of the lever causes the circuit to be made and broken rapidly, throwing
upon the line momentary and sharply defined waves. A dash pot or the fan
regulator is attached to lever to vary alternate signals.
As a modification in the arrangement of the diaphragm sounder I may locate it
in the tertiary circuit of an induction coil, the secondary of which is in the line
and the primary of which includes the transmitter so that the diaphragm sounder
will be worked by induction from the line.
.
Dated this 22nd day of June 1885.

page_text: I THOMAS JOHN HANDFORD of 42 Southampton Buildings in the County of
Middlesex, Patent Agent 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:-
The object of this invention is to increase the capacity of telegraph lines in a
simple and practical manner by the production of instruments and connections
permitting the transmission of two sets of Morse signals back and forth over
the line at the same time, without interfering one with the other, and not only
between terminal offices, but between a terminal office and any intermediate office,
or between intermediate offices alone.
The invention is especially applicable to local lines or to lines having several
offices upon them, to which it can be applied at small expense, each office upon the
line being provided with instruments for transmitting and receiving a second set
of signals and with devices for making the two sets of signals independent and for
insuring against their interference.
Not only is the capacity of the telegraph lines doubled, but the delays occasioned
on lines with several offices by the interfering of two or more operators in their
attempts to gain possession of the line are diminished.
In order that the said Invention may be perfectly understood I shall now, proceed
particularly to describe the same and for that purpose shall refer to the several
figures on the accompanying sheets of drawings the same letters of referenco
indicating corresponding parts in all the figures.
Referring first to figures 1 to 4 of the drawings,
I
1
Figure 1 is a view in diagram of a line with three offices (marked respectively 1,2
and 3) embodying the invention;
Figure 2, a view on a larger scale of the apparatus for one office;
}:
Figure 3 a view of the apparatus for one office with a modified arrangement of
parts; and
"
Figure 4 a view of a further modification.
A line L, L, is employed as usual grounded at its ends and having the ordinary
main battery M, B.
Each office (both terminal and way) has a set of Morse instruments, as shown in
figures 2 and 3, composed of a key band a relay a controlling circuit of a sounder c
and local battery L, B. The usual circuit closing switch which forms a part of the
key b is omitted from the drawings for the sake of simplicity, the arrangement
and action of the ordinary Morse instruments being well understood.
With these ordinary Morse instruments, telegraphing is carried on by Morse
signals in the usual way.
At each office is a device working independent of the main battery, and acting
to induce in the line impulses of high tension.
This device-is composed of an induction coil D, the secondary circuit of which
may be located directly in line as shown in figures 1, 2 and 4. The primary

page_text: circuit of this coil includes a battery d and a back point key F. Or in place of the
key F, a back point sounder F1 worked by a key F and local battery may be
used, as shown in figure 4.
The ordinary Morse key b is shunted by a condenser G so that the line will
always be closed for the induced currents. This condenser also preferably shunta
the relay for a purpose that will be presently set forth. To receive these induced
currents, there is provided at each office a diaphragm sounder H, which is preferably,
as shown in figures 2 and 3, constructed upon the principle of the electro-motograph,
the diaphragme being kept under tension by a spring f, held by friction upon a
revolving chalk cylinder g. The chalk cylinder is rotated continuously by a motor,
electric or mechanical, and the circuit is closed through the spring and oylinder.
This construction of instrument is a well known telephone-receiver and hence
does not require further description here. For the diaphragm sounder, however, a
magneto-electric telephone or other form of telephone-receiver may be used.
The diaphragm sounder at each office is preferably located in circuit with a
condenser I, and this circuit is preferably a shunt around a resistance located in
the line, as shown in figures 1 and 2, which resistance is preferably formed by the
coils of an electro-magnet K.
The circuit at each office, including diaphragm sounder H and condenser I,
instead of being a shunt around a magnet in line, may be a grounded earth
connection or leak to earth," as shown in figure 3, and the secondary circuit of
the induction coil D, instead of being directly in line, may be in a condenser
circuit, whether that circuit is a shunt around a magnet in line or a leak to earth.
By the manipulation of the back point keys F (or the working of the back
point sounders F₁) signals are thrown upon the line in the form of momentary and
sharply defined waves which are responded to only by the diaphragm sounders,
the regular Morse relays not acting quick enough to respond to these waves.
The regular Morse keys being shunted by condensers, the line is always closed
to the high tension induced currents, and since such condensers have what is
equivalent to a low resistance on the instant of closing circuit, it will be seen that
a free path is always provided for the momentary impulses of induction. By
extending these condenser shunts to include the relays as well as the keys, a
desirable result is obtained, in that the counter-electro motive force set up by the
relay magnet effectively stops the passage of the induced impulses by way of the
key and relay and makes the condenser circuit practically the only one closed to
these impulses.
The effect of this action is to make the induction circuit of practically the same
resistance whether the regular Morse keys are open or closed.
An additional advantage flows from the fact that the induced impulses are not
absorbed by the relays, and the induction signals are made more distinct for that
reason.
The condenser shunts are however practically open circuits for the quantity
currents used to operate the relays for the regular Morse signals, the condensers
becoming fully charged and of very high resistance in less time than is required
for the relays to act.
By locating the diaphragm sounders in the circuit of condensers I, such sounders
are not affected to the extent of a disturbance of signals by the regular line
quantity currents.
To obtain this result, however, even with the diaphragm sounders in condenser
circuits, it has been found that the capacity of the condensers must be definitely
fixed.
It has been ascertained, that the loudness of sound in the diaphragm sounder
is, within certain limits, quite independent of the capacity of the condenser I in
direct circuit with it, while the disturbing effect of the regular Morse signals in
the diaphragm sounder increases with the capacity of such condenser I. Hence
the capacity of that condenser is reduced below the point of disturbance by the
regular Morse signals,

page_text: On the other hand, it has been found, that the disturbing effect of the regular
Morse signals on the diaphragm sounders is diminished as the capacity of the
condensers G around the key and relay is increased. Hence, these condensers G
are made of large capacity, say several microfarads each, while the condensers I, in
direct circuit with the diaphragm sounders, have a small capacity say a fractional
part of a microfarad each.
When each diaphragm sounder and its condenser are located in a shunt around
a resistance in the form of a magnet K in line, the reverse action of the condenser
and magnet will make the condenser shunt the only path practically closed to the
induced currents and the line the only path closed to the regular quantity line
currents, as before explained with respect to the relation of the Morse relays and
the condensers G shunting them.
The induced impulses thrown by the induction coil D upon the line are produced
by a source of energy (the local battery d in its primary) independent of the main
battery. These impulses are practically the same whether the regular Morse keys
are open or closed. By arranging the operating key F so that the down stroke
will open the primary circuit and the up stroke will close that circuit, the signal
for the down stroke of the key will be louder than for the up stroke, since when
the primary circuit is closed it absorbs to a certain extent the induction, and the
impulse in secondary is weaker than when the primary is opened.
The back point sounder F¹ worked by key F and local battery d¹ operates the
same way.
This difference in the down and up strokes of key is an important one, since if
the two signals required to mark the interval of time denoting a dot or dash were
the same, the receiving operator might be frequently confused by mistaking the
last signal of a dot or dash for the first signal of the next succeeding dot or dash,
and get what is called in telegrapher's parlance the "back-stroke."
The instruments and devices described make a complete system of Morse.
telegraphy whereby over one line may be transmitted back and forth two sets of
Morse signals, produced by different sources of energy, independent of each other
as to loudness and also as to interference in the receiving instruments.
Further modifications of these instruments and devices will now be referred to,
such modifications relating more particularly to a peculiar transmitter for producing
the momentary and sharply defined waves to which the diaphragm sounder responds
and also to the manner of connecting the diaphragm sounder to the line.
These modifications are illustrated in figures 5, 6, 7, 8, 9, 10, 11 and 12 of the
drawings.
Figure 5 is a view in diagram of a line with four offices (marked respectively
1, 2, 3 and 4).
Figure 6 a separate view in diagram of the arrangement for one office,
Figures 7, 8 and 9 views similar to figure 6 of modified arrangements;
Figure 10 a view of a further modification of the transmitter ;
Figure 11 a sectional view of a dash-pot for varying alternate signals; and
Figure 12 a view of another device for the same purpose.
The peculiar transmitter is an instrument constructed to make and break circuit
with great rapidity so as to send for each signal a large number of such momentary
and sharply defined waves. It may be constructed in a variety of ways.
form preferred is a rapidly revolving circuit controller G kept in motion by a
suitable electrical or mechanical motor.
The
This circuit controller may be placed directly in line, as shown in figure 9, but
it is preferred to place it in the primary circuit of an induction coil D, the secondary
circuit of which is directly in the line, as shown in figures 6, 7 and 8, or is in a
condenser circuit connected with the line, as shown in figure 5. This condenser
circuit may be a ground connection from line, or a shunt around a resistance or
magnet in line. In the primary circuit of the induction coil D, is a battery d, and
in a shunt around the revolving circuit controller G¹, is a sounder F³, with both
its front and back points connected in circuit and operated by a key F" and local

page_text: battery d, as shown in figures 5 and 6. In place of a sounder, a key F (figures 7,
8 and 9) may be employed connected to close circuit at front and back points.
Normally, the sounder or key closes this shunt at its back contact, and the
revolution of the circuit controller does not affect the induction coil. The move-
ment of the sounder lever (or the key) first breaks this shunt at its back point
and then closes it at its front point. During this interval, while the shunt circuit
is open, the circuit controller produces a series of waves in the primary of the
induction coil, and the secondary of such coil throws upon the line a large number
of momentary and sharply defined waves. The return movement of the sounder
lever, or the key, first opens and then closes the shunt circuit, producing the same
result as in its forward movement. The momentary and sharply defined waves do
not work the relays, but are responded to by the diaphragm sounders, and are
translated by them into sound, the intervals between the signals representing dots
and dashes. The number of waves transmitted for each signal is sufficiently great
to make a corresponding number of air waves audible, and hence the sound is
transmitted electrically, instead of being produced by a mechanical blow which is
the result of a single electrical impulse, (as at an ordinary Morse sounder).
To make the signal different for the down and up strokes of the key, the lever
of the working sounder F³, controlling shunt around circuit breaker, is connected
with a dash-pot J (see detail figure 11) the plunger j of which has a valve h
opening in one direction, so that the sounder lever will have a quicker movement
in one direction than the other.
This movement is preferably made quicker on the up-stroke of the key, causing
the second signal marking the interval denoting a dot or dash to be weaker or
shorter or of different tone from the first signal. This prevents confusion in
receiving.
Instead of a dash-pot with valved plunger for varying alternate signals, a device
shown in figure 12 can be used, consisting of a retarding fan i, secured to a spindle
with a ratchet-wheel k. A toothed wheel 7, loose on the same spindle, has a pawl m,
which engages with the ratchet-wheel k.
The sounder lever has on its end a toothed sector n, engaging with the toothed
wheel. The movement of the sounder lever in one direction will turn the fan;
in the other direction the toothed-wheel turns free of the ratchet-wheel k.
The transmitter may be constructed in another form, as shown in figure 10.
A magnet F, worked by a key F and local battery d', operates a lever o, which
is extended the required distance to get the necessary movement. At its end, the
lever carries a finger p, playing over the surface of a contact block L. This
contact block has its face composed of a large number (preferably fifty or more) of
thin plates separated by insulation. This contact block L', and the lever o are
connected. in circuit preferably in the primary of induction coil D, and the move-
ment of the lever o causes the circuit to be made and broken rapidly, throwing
upon the line momentary and sharply defined waves. A dash-pot J, as shewn, or
the fan regulator, is attached to lever o to vary alternate signals.
A modified arrangement for the diaphragm sounder H, is to locate it in the
tertiary circuit of an induction coil D (as shown in figure 6) the secondary of
which is in the line, and the primary of which includes the transmitter, so that
the diaphragm sounder will be worked by induction from the line.
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 :-
1st The combination with a telegraph line, Morse telegraph instruments, and a
source of electrical energy for operating the same, of a Morse signal transmitter,
having a separate source of electrical energy, and throwing momentary and sharply
.defined waves upon the line, and a diaphragm sounder responding to such impulses,
substantially as herein before described.

page_text: 2nd In a system of Morse telegraphy, the combination, for the transmission and
reception of Morse signals, of a telegraph line, an induction coil having secondary
connected with the line, a source of energy and Morse signal transmitter in the
primary of the induction coil, and a diaphragm sounder receiving the induced
impulses, substantially as herein before described.
3rd In a system of Morse telegraphy, the combination with a telegraph line and
Morse instruments, of a diaphragm sounder, and a signal transmitter, transmitting
momentary and sharply defined waves and producing alternately varying signals
at the diaphragm sounder, substantially as hereinbefore described.
4th The combination with a telegraph line, and Morse telegraph instruments,
of a diaphragm sounder located in a condenser circuit connected with such line,
and a signal transmitter to which such diaphragm sounder responds, substantially
as herein before described.
5th The combination with a telegraph line, and Morse telegraph instruments, of
induction transmitters and receivers connected with such line, and condenser-shunts
around the Morse keys, substantially as hereinbefore described.
6th The combination with a telegraph line, and Morse telegraph instruments, of
condensers located in shunts around the Morse keys, and diaphragm sounders
connected in condenser circuits with the said line, the key condensers being of
greater capacity than the sounder condensers, and the relative capacity of the
condensers being such that the disturbance of the diaphragm sounders by the
regular Morse signals is prevented, substantially as herein before described.
7th The combination with a telegraph line, of a diaphragm sounder receiving
Morse signals produced by momentary and sharply defined waves, a resistance or
magnet in line around which the said sounder is shunted, and a condenser in the
said shunt circuit, substantially as hereinbefore described.
8th In a system of Morse telegraphy, the combination with ordinary Morse
telegraph instruments, shunted to keep the line constantly closed to momentary
and sharply defined waves, of diaphragm sounders, and transmitters transmitting
Morse signals electrically by throwing upon the line for each signal a large number
of momentary and sharply defined waves, which do not work the Morse relays,
but are responded to by the diaphragm sounders, substantially as hereinbefore
described.
9th In a system of Morse telegraphy, the combination with a diaphragm sounder,
of a transmitter constructed to make and break circuit rapidly a large number of
times for each movement of the controlling key, and means for retarding the
movement of the transmitter in one direction, so as to vary alternate signals,
substantially as herein before described.
10th In a system of Morse telegraphy, the combination with ordinary Morse
telegraph instruments, shunted to keep the line constantly closed to momentary
and sharply defined waves, of a transmitter of such waves, and a diaphragm sounder
responding to such waves and connected inductively with the line, substantially as
herein before described.
11th The apparatus for duplex signalling on way lines substantially as herein-
before described with reference to the accompanying drawings.