IMPROVEMENTS IN APPARATUS RELATING TO THE ART OF MULTIPLE TELEGRAPHY
Year: 1877

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for the
Invention of "IMPROVEMENTS IN APPARATUS RELATING TO THE ART OF
MULTIPLE TELEGRAPHY." A communication from abroad by Elisha Gray, of
Chicago, in the State of Illinois, United States of America.
Sealed the 28th August 1877, and dated the 22nd June 1877.
PROVISIONAL SPECIFICATION left by the said Sydney Pitt at the Office of
the Commissioners of Patents on the 22nd June 1877.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN APPA-
RATUS RELATING TO THE ART OF MULTIPLE TELEGRAPHY." [A communication
from abroad by Elisha Gray, of Chicago, in the State of Illinois, United States of
America.]
This Invention relates to electro-harmonic telegraphs of the class shown and
described in the Specifications of several Letters Patent, respectively numbered
2646 of 1874, 974 of 1875, and 1874 of 1876.
The object of this Invention is to transmit a number of messages simultaneously
on a single wire, and to adapt the same wire for the simultaneous transmission both
of through and way messages, which ends are attained by transmitting simulta
neously over the same circuit messages by the Morse system, and also by the electro-
harmonic or telephonic system.
Also, further, by combining in a common circuit an electro-harmonic or telephonic
apparatus and a Morse apparatus, with a resistance coil applied to each transmitting
key of said Morse apparatus, whereby the resistence is cut out while the
Morse key is closed, and the circuit is not broken when a Morse key is open,
thus allowing the telephonic instrument to work regardless of the working of the
Morse instrument.
In working under the improved system each station is provided with the usual
Morse apparatus, including key and relay, with the addition of a common resistance
coil or of its equivalent compensating battery herein mentioned in connection with
a Morse transmitting key. Each station is also provided with electro-harmonic or

page_text: telephonic transmitters and receivers, which may be such as shown and described
in the Specifications above referred to, the harmonic or telephonic portion of the
apparatus being connected on circuit, and operated in the manner described in the
Specification, No. 1874 of 1876, above mentioned.
The operation of the improved system will readily be understood by reference to
the accompanying diagram, in which Figure 1 shows two terminal stations A, C,
and an intermediate station B.
Each station is provided with a set of Morse instruments a, b, c. The terminal
stations are each provided with the requisite number of telephonic transmitters and
receivers D, D¹. The transmitters are kept in constant vibration by a local battery,
not shown in the diagram, and when the key E or E¹ of this apparatus is closed a
portion of the main battery at that terminus is alternately thrown to line and
short circuited, as described in the Specification last above mentioned.
A resistance coil R is arranged in the circuit beneath each key of the Morse
apparatus, so that when the Morse key is closed the resistance coil is shunted
or cut out. When the key is open the resistance coil is in circuit, and the currrent
on the line is so much weakened by this resistance that the Morse relays break circuit
on their locals by the falling back of their armatures.
The vibratory impulses of the telephonic apparatus will not affect the Morse
relays. The Morse keys are all kept closed, except the one that is sending, as in the
case of the ordinary transmission by this system. The opening of the keys will not
open the circuit but lets in a resistance sufficient to so weaken the current as
to allow the relay armatures. to fall back by the retractile.. force of their
springs, the tension of which however is sufficient to overcome the remaining force
..left in the magnet.
All the Morse relays will respond to any of the Morse keys as usual under that
system. If, however, one of the harmonic keys is working at the same time with
those of the Morse system, the analyzers or harmonic relays will respond to its
vibration.
The transmission of a musical tone does not interfere with the working of the
Morse relay, and as the Morse keys do not open the circuit, they do not practically
interfere with the harmonic or telephonic signals.
In working the improved system above described it has been discovered that
when the harmonic vibrations are thrown upon the line, about forty per cent. of
the working effect on a Morse relay placed in the line is lost. In other words, the
steady attractive force of the magnet is not as great by forty per cent. when
vibratory currents are employed as when non-vibratory currents are employed.
This difference between the electric force of the steady and of the vibratory.currents
creates a tendency in the Morse relay to respond to a harmonic key as well as its
own a serious drawback to this method of working, as it causes unsteadiness in the
adjustment of the Morse relay. To avoid this difficulty there is introduced into the
circuit a compensating battery having a strength equal to about forty per cent. of
the regular main battery.
It has also been discovered that the same result may be attained by substituting
a resistance for the compensating battery and working the line in the manner
herein-after set forth.
Sometimes a supplemental battery is substituted in place of the resistance coil
above mentioned as applied to the Morse transmitting key.
Figures 2, 3, and 4 represent apparatus for carrying out the above-mentioned
improvements on the system shown in Figure 1, Figure 2 representing an arrange-
ment upon circuit different from Figure 1, Figure 3 representing a supplemental
battery employed instead of the resistance coil R of Figure 2, and Figure 4
representing the arrangement on circuit when the resistance coil is used. instead of
the compensating battery of the telephonic system shown at Figure 2.
In Figure 2, a represents the compensating battery; b, the main battery; C,
Figure 3, the supplemental battery which takes the place of the resistance coil in
the Morse part of the system shown in Figure 1. D represents what is known in

page_text: duplex telegraphy under the Morse system as a continuity preserving key by which
the compensating battery is shunted in or out of circuit.
It is well known in the art that on the depression of the lever of such
a key, contact is made with a second lever E, pivotted at f, which breaks contact
at the point g.
It will be noticed that when the line is at rest the compensating battery a is
shunted off the line through the wires 1, 2, break point g, and lever E. Now, if
the telephonic key D is depressed while the transmitter his in vibration, the main
battery 6 will be thrown into vibration by contact between the two levers D, E, of
the continuity preserving key, which will diminish the effect on the Morse relays i, i,
about forty per cent.; but at the same instant the two levers D, E, make contact.
The shunt wire 1 is opened at the break point g, thus allowing the compensation
battery a, which in strength is equal to about forty per cent. of the main battery b
(before it was thrown into vibration), to flow to line. By this means an even strength
is kept on the line, and the adjustment of the Morse relay is not in the least dis-
turbed by the working of the telephonic keys.
Instead of the compensation battery a resistance may be used. In that case the
above-described arrangement of the keys would be reversed, leaving the break point
g open when the line was at rest, and the resistance in the line in the place of the
battery as shown at R, in Figure 3. The resistance should be sufficient to reduce
the battery effect upon the line forty per cent.
When the telephonic key is depressed it throws the main battery into vibration
as before, affecting it in the same manner; but the working margin on the line is
kept up by cutting out the resistance which would reduce it forty per cent. On
some lines, and under some circumstances, it is desirable to introduce a battery
instead of a resistance coil in the Morse part of the system. When placed in that
position and shunted off and on the line with a key, it is obvious that the effect
would be substantially the same as cutting in and out resistance. There is this
difference however which in some cases is advantageous. The resistance coil works
the wire by weakening the current below its normal strength, while the battery
C increases its strength when let in by the key, without at the same time adding
to any appreciable extent to the resistance of the line. Thus the improved system
enables to transmit simultaneously through and way messages on the same wire
instead of employing two distinct circuits, as under the present system, in which
separate wires are required for way and through business.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Sydney Pitt in the Great Seal Patent Office on the 21st December.
1877.
SYDNEY PITT, of Sutton, in the County of Surrey. "IMPROVEMENTS IN APPA-
RATUS RELATING TO THE ART OF MULTIPLE TELEGRAPHY." A communication
from abroad by Elisha Gray, of Chicago, in the State of Illinois, United States of
America.
This Invention relates to electro-harmonic telegraphs of the class shown and
described in the Specifications of several Letters Patent, respectively numbered 2646
of 1874, 974 of 1875, and 1874 of 1876.
The object of this Invention is to transmit a number of messages simultaneously
on a single wire, and to adapt the same wire for the simultaneous transmission both
of through and way messages, which ends are attained by transmitting simulta-
neously over the same circuit messages by the Morse system, and also by the
electro-harmonic or telephonic system.
Also, further, by combining in a common circuit an electro-harmonic or telephonic
apparatus and a Morse apparatus, with a resistance coil applied to each transmitting
key of said Morse apparatus, whereby the resistance is cut out while the Morse
key is closed, and the circuit is not broken when a Morse key is open, thus
allowing the telephonic instrument to work regardless of the working of the Morse
instrument.
In working under the improved system each station is provided with the usual
Morse apparatus, including key and relay, with the addition of a common resistance
coil, or of its equivalent compensating battery herein mentioned in connection with
a Morse transmitting key. Each station is also provided with electro-harmonic or
telephonic transmitters and receivers, which may be such as shown and described
in the Specifications above referred to, the harmonic or telephonic portion of the
apparatus being connected on circuit and operated in the manner described in the
Specification, No. 1874 of 1876, above-mentioned.
The operation of the improved system will readily be understood by reference
to the accompanying diagram in which Figure 1 shows two terminal stations A, C,
and an intermediate station B.
Each station is provided with a set of Morse instruments a, b, c. The terminal
stations are each provided with the requisite number of telephonic transmitters and
receivers D, D'. The transmitters are kept in constant vibration by a local battery,
not shown in the diagram, and when the key E or E¹ of this apparatus is closed a
portion of the main battery at that terminus is alternately thrown to line and short
circuited, as described in the Specification last above mentioned.
A resistance coil R is arranged in the circuit beneath each key of the Morse
apparatus, so that when the Morse key is closed the resistance coil is shunted or
cut out. When the key is open the resistance coil is in circuit, and the current on
the line is so much weakened by this resistance that the Morse relays break circuit
on their locals by the falling back of their armatures...
The vibratory impulses of the telephonic apparatus will not affect the Morse
relays. The Morse keys are all kept closed, except the one that is sending, as in
the case of the ordinary transmission by this system. The opening of the keys
will not open the circuit but lets in a resistance sufficient to so weaken the
current as to allow the relay armatures to fall back by the retractile force of their
springs, the tension of which, however, is sufficient to overcome the remaining force
left in the magnet.
All the Morse relays will respond to any of the Morse keys as usual under that
system. If, however, one of the harmonic keys is working at the same time with
those of the Morse system, the analyzers or harmonic relays will respond to its
vibration.

page_text: The transmission of a musical tone does not interfere with the working of the
Morse relay, and as the Morse keys do not open the circuit they do not practically
interfere with the harmonic or telephonic signals.
In working the improved system above described, it has been discovered that
when the harmonic vibrations are thrown upon the line about 40 per cent. of
the working effect on a Morse relay placed in the line is lost. In other words,
the steady attractive force of the magnet is not as great by 40 per cent. when
vibratory currents are employed as when non-vibratory currents are employed.
This difference between the electric force of the steady and of the vibratory
currents creates a tendency in the Morse relay to respond to a harmonic key as
well as its own, a serious drawback to this method of working, as it causes
unsteadiness in the adjustment of the Morse relay. To avoid this difficulty there is
introduced into the circuit a compensating battery, having a strength equal to about
40 per cent. of the regular main battery.
It has also been discovered that the same result may be attained by substituting
a resistance for the compensating battery, and working the line in the manner
herein-after set forth.
Sometimes a supplemental battery is substituted in place of the resistance coil
above mentioned as applied to the Morse transmitting key.
Figures 2, 3, and 4 represent apparatus for carrying out the above-mentioned
improvements on the system shown in Figure 1, Figure 2 representing an
arrangement upon circuit different from Figure 1, Figure 3 representing a
supplemental battery employed instead of the resistance coil R of Figure 2,
and Figure 4 representing the arrangement on circuit when the resistance coil
is used instead of the compensating battery of the telephonic system shown at
Figure 2.
In Figure 2 a represents the compensating battery; b, the main battery; C;
Figure 3, the supplementary battery, which takes the place of the resistance
coil in the Morse part of the system shown in Figure 1; D represents what is
known in duplex telegraphy under the Morse system as a continuity preserving key,
by which the compensating battery is shunted in or out of circuit.
It is well known in the art that on the depression of the lever of such
a key, contact is made with a second lever E, pivoted at f, which breaks contact at
the point g.
It will be noticed that when the line is at rest the compensating battery a is
shunted off the line through the wires 1, 2, break point g, and lever E. Now,
if the telephonic key D is depressed while the transmitter is in vibration the
main battery will be thrown into vibration by contact between the two
levers D, E, of the continuity preserving key, which will diminish the effect
on the Morse relays i, i¹, about 40 per cent.; but at the same instant the
two levers D, E, make contact, the shunt wire 1 is opened at the break point g,
thus allowing the compensating battery a, which in strength is equal to about
40 per cent. of the main battery b (before it was thrown into vibration) to
flow to line. By this means an even strength is kept on the line, and the adjust-
ment of the Morse relay is not in the least disturbed by the working of the
telephonic keys.
Instead of the compensation battery a resistance may be used. In that case the
above described arrangement of the keys would be reversed, leaving the break point g
open, when the line was at rest, and the resistance in the line in the place of the
battery, as shown at R in Figure 3. The resistance should be sufficient to reduce
the battery effect upon the line 40 per cent.
When the telephonic key is depressed it throws the main battery into vibration,
as before affecting it, in the same manner, but the working margin on the
line is kept up by cutting out the resistance which would reduce it 40 per cent.
On some lines, and under some circumstances, it is desirable to introduce, a
battery instead of a resistance coil in the Morse part of the system. When placed
in that position and shunted off and on the line with a key it is obvious that

page_text: ·
the effect would be substantially the same as cutting in and out resistance.
There is this difference, however, which in some cases is advantageous. The
resistance coil works the wire by weakening the current below its normal
strength, while the battery increases its strength when let in by the key,
without at the same time adding to any appreciable extent to the resistance
of the line. Thus the improved system enables to transmit simultaneously
through and way messages on the same wire, instead of employing two distinct
circuits, as under the present system, in which separate wires are required for way
and through business.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the herein-before in part
recited Letters Patent is,-
First. The method of multiple telegraphy herein-before set forth, which consists
in transmitting simultaneously through the same circuit messages on the Morse
and on the electro-harmonic or telephonic system.
Second. The combination, substantially as herein-before set forth, on one wire or
circuit of a Morse apparatus with electro-harmonic or telephonic apparatus, whereby
the two classes of messages simultaneously may be transmitted without interference
through the same circuit.
Third. The combination, substantially as herein-before set forth, in an electric
circuit of an electro-harmonic or telephonic apparatus and a Morse apparatus having
a resistance coil applied to each transmitting key of said Morse apparatus, whereby
the resistance is cut out while the Morse key is closed, and the circuit remains
unbroken when the Morse key is open, thus allowing the telephonic instrument to
work regardless of the working of the Morse instrument.
Fourth. The method of Morse telephonic multiple telegraphy, herein-before set
forth, which method consists in keeping an even electric force upon the line whether
the battery or any portion of it is in vibration or at rest by compensating the
variations in the electric force caused by throwing the telephonic system on or off
the line.
Fifth. In combination, substantially as herein-before set forth, in an electric
circuit of a Morse transmitting and telephonic transmitting apparatus, a main battery,
and a compensating adjustment, whereby the disturbance of equilibrium caused by
the throwing of the telephonic apparatus into and out of line is instantaneously and
automatically compensated.
Sixth. The combination, substantially as herein-before set forth, in a telegraphic
circuit of a main battery, a compensating battery, a telegraphic transmitter, a con-
tinuity preserving key, and a shunt circuit, whereby the equilibrium of the electric
force is preserved.
Seventh. The combination, substantially as herein-before set forth, in an electric
circuit of a main battery, a telephonic transmitter, a continuity preserving key,
a resistance coil, and a shunt circuit, whereby the resistance is thrown off
and on the line to compensate variations in the electric force of the telephonic
system.
Eighth. The combination, substantially as herein-before set forth, with the Morse
part of the system, of a supplemental battery which compensates inequalities pro-.
duced in the electric force by the working of the telephonic system.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand
and seal, this Eleventh day of December, in the year of our Lord One
thousand eight hundred and seventy-seven.
SYDNEY PITT., (L.S.)