IMPROVEMENT OF ELECTRO- MAGNETIC TELEGRAPH APPARATUS
Year: 1854

page_text: PROVISIONAL SPECIFICATION left by Erik Edlund at the Office of
the Commissioners of Patents, with his Petition, on the 23rd November
1854..
I, ERIK EDLUND, of Stockholm, in the Kingdom of Sweden, do hereby
declare the nature of the said Invention for "IMPROVEMENT OF ELECTRO-
MAGNETIC TELEGRAPH APPARATUS" to be as follows:-
The object aimed at by this improvement is that messages may be sent
simultaneously from two stations in opposite directions through the same wire.
Figure 1 shows the general arrangement which I use for this purpose.
B represents the telegraph wire between two. stations A and A¹, both
perfectly alike, so that what is hereafter said of one may also be applied to the
other; D and D' are the galvanic batteries; and C, C', the metallic plates in
the earth; Y, Y', represent the electro-magnets, which when the telegraph is
at work are rendered magnetic by the action of the galvanic current. (In the
case of the needle apparatus, in which the needles are put in motion by the
action of the current, the word electro-magnet in this description should be
replaced by the word needle). The conducting wire going from. one of the
poles of the battery is divided at E into two branches, one of which, a, b, c, in
the usual way surrounds the electro-magnet by several insulated windings.
The other branch, d, e, f, is also wound on the same electro-magnet, though in
an opposite direction, and. goes from thence to F, which point is. by means of
a wire kept in constant galvanic connection with the plate C. Now, if G is
connected with H, the battery will begin to act. Part of the galvanic.current
passes, through the windings a, b, c, to the next station, and there it enters the.

page_text: earth;
the other part goes through the windings d, e, f, and through P, F, G,
to the other pole of the battery; both parts of the current, therefore, pass
around the electro-magnet in opposite directions, and consequently counteract
each other. If, then, the number of windings in a, b, c, is to the number of
windings in d, e, f, in the same proportion as the force of the current
in the latter is to the force of the current in the former, the action of
the electro-magnet of one part of the current must exactly counterbalance
the action of the other part, and, the electro-magnet consequently must
remain unmagnetized. But the proportion between the force of that part
of the current which goes to the next station and the force of the other
part which goes through the conductor d, e, f, P, H, depending on the pro-
portion between the galvanic resistance-of-the--whole line and that of the
conductor d, e, f, P, H, and not only the last-named resistance, but also the
number of windings being entirely,arbitrary, it will of course always be possible.
to produce the said compensation.
When a galvanic current-comes-from-the-station-A it must first pass round
the electro-magnet Y in the direction c, b, a. If, then, G is not connected
with H, the whole current must pass through d, e, f, to F, and thence to the
plate C. Hence it appears that the current, which comes from the other station
traverses the windings c, b, a, and d, e, f, in the same direction round the
electro-magnet, in consequence whereof the effect produced by the joint action
of all the several windings is increased. The same thing takes place if. G
is connected with H, only with this difference, that in this case part of the
galvanic current goes from E through the battery D. to C. Hence it follows
that the electro-magnet is acted upon by the current which comes from the
next station, while that current which originates at the station where the
electro-magnet itself is placed exercises no influence whatever,. and thus
the necessary condition is.fulfilled for simultaneously sending messages between
the two stations.
1
It may be objected that the resistance against that part of the current which
goes from A to A' is depending on whether the battery at A' is closed or open;
that is to say, whether H is galvanically connected with G¹ or not. These
points being connected, the current is divided at E', and a part thereof goes
through the battery D', and further to H', in consequence whereof the resis-
tance becomes less than when the whole current is to pass through d¹, e¹, f",
on its way to H¹. Thus, the resistance against the current going between
the two stations varies while telegraphing in opposite directions. These varia-
tions, however, are evidently depending on the resistance in the conductor
d', e, f, P, H, and this. resistance: not being very considerable, the-said

page_text: variations-do-not-exercise-any-pernicious-influence_on_the
working_of_the_
telegraph. In the experiments which I-have made in order to ascertain the
practibility of my method, the resistance in d, e, f, PH, has been about
one-fifth of the resistance between the stations. Besides, the difficulties here
mentioned may be entirely removed by means of a little change in the
arrangement which is represented in Figure 2. The letters D, E, C, Y,
a, b, c, d, e, f, have the same signification as in Figure 1; but the key, -by
means of which the current is closed and opened, and which in Figure 1 is
placed on the conductor between one of the poles of the vóltaic battery
and the earth plate, is here removed to. N; that is to say; to the conductor
between the other pole and the point of division E in the current. This'
key, which by a separate conductor R, S, is connected with the earth plate C,
is besides so constructed as to close the conductor D, N, E, at the same
moment it opens the conductor S, R, E, and vice versa.. In this way the
current. which arrives from the other station, whatever may be the position of
the key, must always divide itself at E, and one part thereof go to the earth
plate either through E, N, D, or E, R, S., If, then, there is inserted in the
conductor R, S, 'a resistance of about the same magnitude as the resistance in?
the battery, the resistance must be nearly the same under all circumstances. **
From what has been said it appears that the arrangement of the apparatus
must essentially depend 'on the resistance between the stations. In order to
avoid the necessity of having a different apparatus at each station, and also
the difficulties which might arise from occasional changes in the resistance
between the stations, the apparatus ought to be so constructed that both the
number of windings and the resistance in the conductor d, e, f, P, H, may be
easily changed. This can of course be effected in several ways. Figures 3*
and 4 represent the manner in which for my experiments 'I have' modified,
a Morse's "relais," and it is evident that the same modification may be
applied to any other electro-magnetic telegraph apparatus.
Figure 3 represents this arrangement as viewed from above, and Figure 4
as viewed from the side. G, G', (Figure 3,) is a board. in which the brass
bar h, h', and the 'brass pieces S¹, SS are fixed. The latter
are insulated from each other as well as from the brass bar.. X, X-represent.
a horizontal section of a vertically standing electro-magnet (In the case of a
needle apparatus, the electro-magnet is here to be replaced by a 'magnetic
needle suspended' in the way usual in this kind of electro-magnetic telegraph):
m!, m², m³, m³, m³, are plugs of brass which, may be removed' from one place to
another in order to produce metallic connection between two neighbouring
brass pieces, or between any of them and the brass bar.,,,aré

page_text: coils of metallic wire overspun with silk. These coils have no other object
than to produce a resistance against the galvanic current. The ends of the
wire of each coil are connected with the mictallic pieces S³,
shown in Figure 3.
S¹³, as
The galvanic current from the battery passes through the conducting wire
_to-the-metallic-piece-s,-where-it-is-divided. One-part-goes-through-the-plug m
to the metallic pieces S³, thence through the windings around X and X', and
further through the conducting wire p to S¹s; then it passes over the plug m
to S and is lastly conducted through the wire p to the next station. The other
part of-the-current is conducted through the wire q, around X and X, and
passes through q to the metallic piece S³. This conducting wire is wound on
the electro-magnet (or the magnetic needle) in the opposite direction to the
wire P. From Ss there goes another conducting wire q³, wound on the electro-
magnet (or the magnetic needle) in the same direction, as q, q', and by
means of connected with the metallic piece S7. The other wires q', 1', 9,
9, 99, 90, 9, are wound in the same direction as the two last named. If
now the plugs m² and m³ have the place shown by Figure 3, the said part of
the current goes through 7, 9;. 79, passes then through the metallic
bar h, h', and the plug m³, to the metallic piece S10, whence it is further con-
ducted through the coils 2, 3, 4, 2, to the metallic piece S, and lastly through
the plug m¹ to S¹³, which latter, by means of the wire t, is connected with the
other pole of the voltaic battery. The conductor S', 7, 7',
q", h, h¹,
22, 73, S¹³, t, consequently corresponds to what is called E, d, e, f, P,
F, H, in Figure 1. If the metal plug m³ is removed to any of the other
metallic pieces, the number of windings on the electro-magnet X and X¹-will
be changed, and consequently also the magnetic action of the current. The
galvanic resistance may also be changed in the same way by removing the
plug m³..
A "relais" of Morse's construction, provided with the improvement here
described, may in the following manner easily be changed into a common
"relais." For this purpose, the plug m is removed and placed between S¹
and S1, the plug m³ between S1 and S20, m³ between h, h', and S, and finally,
m³ between S and S". Besides this, a common key of Morse's construction is
inserted at F (Figure 1), so that F is in galvanic connection with H only
when the battery at A is inactive, while, as soon as the battery comes into
activity, the connection between F and H is interrupted. The current coming
from the battery and passing through the wire l is by this means led through
the wire w to S20, and thence through the wire p to the next station. The
current going to the next station does not consequently go around the electro-

page_text: -magnet; on.the.
station goes through w to S, thence through the windings q, q',
.
2º,
to S', then through the brass bar h, h', the metallic pieces S6 and S¼, and
the conducting wire y to S¹; after which it passes through the other windings
p, around the electro-magnet to S³, and, finally, through u, S", S1, and the
conducting wire t into the earth plate C.
What I claim as my Invention is, the application in electro-magnetic
telegraph apparatus of a branching off of the galvanic current in the manner
above described, so as to produce the simultaneous sending of two telegraph
messages from different stations in opposite directions through the same
conducting wire.