Improvements relating to Duplex Electric Telegraphs.
Year: 1888

page_text: Date of Application, 13th Dec., 1888
Complete Specification Left, 13th Sept., 1889-Accepted, 19th Oct.,
1889
PROVISIONAL SPECIFICATION
Improvements relating to Duplex Electric Telegraphs.
I, HERBERT ARNAUD TAYLOR, of 4, Great Winchester Street, in the City of London,
Civil Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to duplex electric telegraphs and comprises various improve-
ments which are applicable to telegraphs worked on the "differential" systein and
also to those worked on the "bridge" system.
An important feature of my said invention is the employment of a compensation
circuit comprising one or more electro-magnets wound with one or more wires as
hereinafter described. In some instances Ï use, in combination with such electro-
magnets, suitable condensers and resistances.
My improved compensation circuit is particularly well adapted for balancing short
telegraph cables or such as are worked with a relay. It is, however, also advantageous
for use with long cables either by itself or in conjunction with an artificial line, such
as Muirhead's or Stearn's, having resistance and electrostatic capacity.
According to one method of applying my said invention to a telegraph to be worked
on the "differential" system, I proceed as follows, viz. -I provide an electro-
magnet with a laminated iron core and wound with primary and secondary coils, the
primary being a wire of larger diameter and of smaller length and resistance than the
secondary. I connect one wire or circuit of the differential receiving instrument with
the cable and with the transmiting key, and I connect one end of the other wire or
circuit of the said receiving instrument with the said key, and the other end thereof,
through an adjustable resistance, with one terminal of the secondary coil of the said
electro-magnet, the other terminal of this coil being connected with the earth. The
primary coil of the said magnet 1 connect with the aforesaid key, and, through an
adjustable resistance, with the earth in such a manner that the currents from the key
will pass in reverse directions through the coils of the said magnet. I also connect
the second wire of the receiving instrument (i.e. the wire thereof last above mentioned),
through an adjustable resistance, with one pole of a condenser, the other pole of
which is to earth. The iron core of the said electro-magnet is made adjustable so that
it may be more or less withdrawn from the coils to regulate the action or effect of
the compensation circuit. Or the coils are made adjustable on the core for this
purpose.
In using the apparatus constructed and arranged as above described, the resistance
between the second wire of the receiving instrument and the said electro-magnet is
first adjusted until, on completing the battery-circuit by means of the key, the
"steady" currents in the two circuits of the receiving instrument exactly compensate
or balance one another, so that there will be no action or effect upon the needle or
tongue of the said instrument. The first rush or sudden flow of current into or from
the cable, on making or breaking contact by means of the key, is then compensated
by increasing or diminishing the resistance between the primary coil of the magnet
and the earth, or by adjusting the core or the coils of the magnet so as to allow a
greater or less length of the said core to be influenced by the coils, until the best
results are obtained. A final adjustment is, if necessary, effected by means of the
resistance and condenser between the second wire of the receiving instrument and the
earth.
When condensers are used for working the cable and there is consequently no com-
plete conducting circuit in the line-branch of the receiving instrument, I modify my
compensation circuit by connecting the adjustable resistance at one end of the secondary
coil of the magnet with the transmitting key, instead of with the earth, so as to form a com-
plote metallic circuit through one branch of the receiving instrument. In the case of a

page_text: very long cable, it may be expedient to introduce a length of artificial line, such as
Muirhead's or Stearn's, having resistance and eloctrostatic capacity, the induction
plate of which is connected either with the earth or with another part of the circuit.
For duplex working by the "bridge" system, the arrangement of the apparatus is
modified as hereinafter described, that is to say, assuming that the two branches of
the differential instrument above referred to have equal resistances, as is usually the
case, and that a duplex balance is obtained. A point in the cable-circuit and a point
in the compensation circuit are connected to the terminals of a receiving instrument
in a well-known manner, so that the said instrument will be unaffected by the current
applied when the transmitting key is operated. Plain coils of the samo resistance as
the branches of the aforesaid differential instrument are substituted for the latter,
without disturbing the balance. The whole arrangement is then adapted to work upon
the "bridge" system of duplex telegraphy, the receiving instrument being affected
by currents received from the distant end of the cable, but not by those transmitted
thereto.
On short cables worked without condensers in the cable-circuit, I have found that
it is not necessary, in order to obtain a duplex balance by the "bridge" system,
to have the electro-magnet wound with two circuits, as the self-induction of a single
coil wound on a core and placed in the arm of the bridge conjugate to that formed by
the cable is sufficient with small adjustments of condensers and resistances to com-
pensate for the electrostatic charge of the cable.
I sometimes, however, employ an electro-magnet with two coils which are connected
at one end with the key, the primary being connected at its other end through an
adjustable resistance with the earth, and the secondary, which forms one arm of the
bridge, being connected at its other end with a Muirhead's or other artificial line and
with one of the terminals of the receiving instrument.
The remote end of the said artificial line is left "free" if condensers are used for
working the cable, otherwise it is put to earth.
The arm of the bridge which is connected at its one end with the key and at its
other end with a terminal of the receiving instrument and with the cable or with the
working condensers, consists of an ordinary adjustable resistance.
In some cases, it may be necessary or desirable to introduce a small electro-magnet
with a closed magnetic circuit on the cable-side of the apparatus, in order to
neutralize the effect of any inequality of balance on the reversal of the current.
For
In the construction of the electro-magnet for the purpose above specified, I some-
times find it advantageous to place more than two circuits or coils upon the core.
instance, I place thereon threo circuits, the tertiary having its ends connected through
a suitable resistance and thus forming a closed electro-magnetic circuit to be used as
an adjustment.
Dated this 12th day of Dec 1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements relating to Duplex Electric Telegraphs.
I, HERBERT ARNAUD TAYLOR, of 4 Great Winchester Street, in the City of
London, Civil Engineer, 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 :—
My invention relates to duplex electric telegraphs and comprises various improve-
ments which are applicable to telegraphs worked on the "differential" system and also
to those worked on the "bridge" system.
An important feature of my said invention is the employment of a compensation
circuit comprising one or more electro-magnets wound with one or more wires as
hereinafter described, and having either closed or open magnetic circuits. In some

page_text: instances, I use, in combination with such electro-magnets, suitable condensers and
resistances.
My improved compensation circuit is particularly well adapted for balancing short
telegraph cables or such as are worked with a relay. It is, however, also advan-
tageous for use with long cables either by itself or in conjunction with an artificial
line, such as Muirhead's or Stearns', having resistance and electrostatic capacity.
In the accompanying drawing I have shown how my said invention may be con-
veniently and advantageously carried into practice.
Figures 1 to 5 are diagrams showing different arrangements of duplex electric
telegraphs having my present improvements applied thereto.
Figure 6 is a diagrain showing an electromagnet hereinafter described for use as
a compensation circuit.
Like letters indicate corresponding parts throughout the drawing.
C is the cable. K the transmitting key, B the battery connected therewith.
the two wires or circuits of a differential receiving instrument.
a, b are
According to one method of applying my said invention to a telegraph to be worked
on the "differential" system, I proceed as hereinafter described with reference to
Figure 1, viz. I provide an electro-magnet having a laminated iron core c and
wound with primary and secondary coils d, e, the primary d being a wire of larger
I connect the
diameter and of smaller length and resistance than the secondary e.
wire or circuit a of the differential receiving instrument with the cable C and with
the transmitting key K, and I connect one and of the other wire or circuit of the
said receiving instrument with the said key, and the other end thereof through an
adjustable resistance with one terminal of the secondary coil e of the said electro-
magnet, the other terminal of this coil being connected with the earth. The primary
coil d of the sail magnet I connect with the aforesaid key and through an adjustable
resistance with the earth, in such a manner that the currents from the key will
pass in reverse directions through the coils of the said magnet. I also connect
the wire b of the recoiving instrument through an adjustable resistance, with
one pole of a condenser the other pole of which is to earth. The iron core
of the said electro-magnet is made adjustable so that it may be more or less with-
drawn from the coils to regulate the action or effect of the compensation circuit.
Or the coils are made adjustable on the core for this purpose.
"
In using the apparatus constructed and arranged as above described, the resistance r
between the wire of the receiving instrument and the said electro-magnet is first
adjusted until, on completing the battery-circuit by means of the key, the "ste.uly
currents in the two circuits of the receiving instrument exactly compensate or balance
one another, so that there will be no action or effect upon the needle or tongue of
the said instrument. The first rush or sudden flow of current into or from the cable,
on making or breaking contact by means of the key, is then compensated by increasing
or diminishing the resistance between the primary coil d of the magnet and the
earth, or by adjusting the core or the coils of the magnet so as to allow a greater or
less length of the said core to be influenced by the coils, until the best results are
obinined. A final adjustment is, if necessary, effected by means of the resistance **
and condenser C¹ between the wire b of the receiving instrument and the earth.
When condensers, as at C Figure 2, are used for working the cable, and there
is consequently no complete conducting circuit in the line-branch of the receiving
instrument, I modify my compensation circuit by connecting the secondary coil e of
the magnet directly with the transmitting key, instead of with the earth as shown in
Figure 1, so as to form a complete metallic circuit through one branch of the
receiving instrument.
In the case of a very long cable, it may be expedient to introduce between the
secondary and the transmitting key, a length of artificial line A. L., Figure 3, such
as Muirhead's or Stearns', having resistance and electrostatic capacity, the induction
plates of which are connected either with the earth or with another part of the circuit.
An adjustable resistance is preferably placed between the conducting circuit of the
artificial line and the transmitting koy.

page_text: For duplex working by the “bridge” system, the arrangement of the apparatus is
modified as follows, that is to say, assuming that, in the arrangement above described,
the two branches of the differential instrument hava equal resistances, as is usually
he case, and that a duplex balance is obtained, a point in the cable-circuit and a
point in the compensation circuit are connected to the terminals of a receiving
instrument in a well known manner, as indicated by dotted lines at R in Figures 1,
2 and 3, so that the said instrument will be unaffected by the current applied when
the transmitting key is operated. Plain coils of the same resistance as the branches
of the aforesaid differential instrument are substituted for the latter, without disturbing
the balance. The whole arrangement is then adapted to work upon the "bridge,
system of duplex telegraphy, the receiving instrument being affected by currents
received from the distant end of the cable but not by those transmitted thereto.
On short cables worked without condensers in the cable-circuit, I have found that
it is not necessary, in order to obtain a duplex balance by the "bridge" system, to
have the electro-magnet wound with two circuits, as the self-induction of a single
coil & wound on a core e and placed in the arm of the bridge conjugate to that formed
by the cable, as shown in Figure 4, is sufficient, with small adjustments of
condensers 0, ("and resistances, 76, to effectually compensate for the electrostatic
charge of the cable.
I sometimes, however, employ an electro-magnet with two coils d, e, Figure 5,
which are connected at one end with the key, the primary d being connected at its
other and through an adjustablo resistance with the earth and the secondary e,
which forms with an adjustable resistance 7 one arm of the bridge, being connected
at its other end, through the adjustable resistances and, with a Muirhead's,
Stearns' or other artificial line A. L., and with one of the terminals of the receiving
instrument.
The remote end of the said artificial line is left "free" if condensers are used for
working the cable, otherwise it is put to earth.
The arm R' of the bridge, which is connected at its one end with the "key" and
at its other end with a terminal of the receiving instrument and with the cable or
with the working condensers, consists of an ordinary adjustable resistance.
It is sometimes necessary or desirable to introduce a small electro-magnet on the
cable side of the apparatus between the cable and the receiving instrument, in order to
neutralize the effect of any inequality of balance on the reversal of the current. I prefer
to employ for this purpose an electro-magnet having a closed magnetic circuit.
In the construction of the electro-magnet for my improved compensation circuit
herein described, I sometimes find it advantageous to place more than two secondary
circuits or coils upon the core and to connect one or more of these secondary coils
with adjustable resistances so as to form closed circuits. For instance, I arrange on
the said core three circuits or coils d, e, e¹; one of the secondaries, e, having its ends
connected through a suitable resistance, as illustrated in Figure 6 of the drawing,
thus forming a closed electro-magnetic circuit to be used as an adjustment.
By my improvements I effect great economy in respect of the cost of manufacture
of duplex electric telegraph apparatus.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I wish it understood that
1 claim -
First In a duplex electric tolegraph, a compensation circuit comprising one or
more electromagnets wound with one or moro wires, substantially as herein before
described, whether such electromagnets are constructed with closed or with open
magnetic circuits, for the purposes above specified.
Second-The combination, with the cable and the transmitting key, of an electro-
magnet wound with primary and secondary coils so connected with the said key and with
one wire or circuit of a differential receiving instrument or one arm of a bridge, that
the currents from the key will pass in reverse directions through the said coils,
substantially as, and for the purpose, set forth.

page_text: Third-The combination, with my improved compensation circuit, of an artificial
line or a portion of an artificial line having resistance and electrostatic capacity,
substantially as, and for the purpose, set forth.
Fourth The combination, with my improved compensation circuit, of an electro-
magnet having a closed magnetic circuit, placed between the cable and the combined
receiving and transmitting apparatus, for the purpose above specified.
Fifth The apparatus comprising the improved compensation circuit and the
adjustable resistances (with or without the portion of Muirhead's, Stearns' or other
artificial line) arranged substantially as described with reference to either of the
Figures 1, 2, 3, 4 or 5 of the accompanying drawing, for the purposes above specified.
Sixth An electro-magnet having three or more coils one or more of which are
connected with adjustable resistances so as to form closed electro-magnetic circuits,
for the purpose above specified.
2009.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.