IMPROVEMENTS IN ELECTRIC TELEGRAPHS, WHICH IMPROVE- MENTS REFER PARTLY TO AN IMPROVED RELAY OR ELECTRO-MAGNET, WHICH MAY BE EMPLOYED ALSO IN ANY INSTRUMENT OR CONTRIVANCE WHERE RELAYS OR ELECTRO- MAGNETS WITH COUNTERACTING SPRINGS ARE USED
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by James Angelo Fahie at the Office of the
Commissioners of Patents on the 3rd February 1876. A communication from
abroad by John Joseph Fahie, of Shiraz, Persia.
JAMES ANGELO FAHIE, of the Office for Patents, No. 2, Nassau Street, in the City
of Dublin, Ireland. "IMPROVEMENTS IN ELECTRIC TELEGRAPHS, WHICH IMPROVE-
MENTS REFER PARTLY TO AN IMPROVED RELAY OR ELECTRO-MAGNET, WHICH MAY BE
EMPLOYED ALSO IN ANY INSTRUMENT OR CONTRIVANCE WHERE RELAYS OR ELECTRO-
MAGNETS WITH COUNTERACTING SPRINGS ARE USED."
This Invention has for its object improvements in electric telegraphs, which
improvements comprise an improved relay or electro-magnet, which may be employed
also in any instrument or contrivance where relays or electro-magnets with counter-
acting springs are used.
As regards the first part of the Invention, my foreign correspondent claims to
have so simplified the art of duplex working that two stations connected by a
telegraph wire can signal simultaneously from both ends, provided that in addition
to the ordinary apparatus for single working each station has a simple rheostat or
set of resistance coils.
The one has its
Fig. 1 shews the general arrangement or combination of the apparatus by which I
effect this object. B, Bo, are voltaic batteries of equal or approximately equal
internal resistance and electro-motive force, and by preference any pattern of small
internal resistance, such, for example, as the ordinary Daniell.
copper or positive pole joined permanently to line, the other its zinc or negative
pole, the remaining poles being to earth. R, Ro, are relays of any, pattern, but by
preference unpolarized relays, and especially that arrangement of unpolarised relays
which is herein-after described as forming a part of the Invention communicated
to me as aforesaid. S, So, are ordinary galvanoscopes, but should be fairly
sensitive.
R, B, R, Bo, are ordinary rheostats, but by preference that style known as the
resistance slide or some similar arrangement. K, Ko, may be ordinary Morse keys,
the back stops of which are unoccupied or insulated, the front stops being connected
direct to earth. To the lever of each key a wire is joined having at its free end a
travelling or experimental peg.
The commutators A, Ao, extra keys K 1 and K 2, and the earth blocks E and Eo
are not required for duplex working; I have introduced them for the sake of
гр

page_text: completeness, so y Ե
as well as for duplex transmission, as will be hereafter described.
Any station as I have said provided with the ordinary signalling apparatus
above-mentioned and a rheostat is in a position to work duplex, but in what
follows I shall suppose that each station has those pieces of apparatus to which I
have just given the preference, for I find that adjustment is simplified and better
results are obtained by their use. Let therefore B and Bo be Daniell batteries of
the requisite strength, each having the same number of cells and as little internal
resistance as possible. Let R, B, and R, Bo, be rheostats on the principle of the
Thomson slide, and let R and Ro be for the present fairly sensitive unpolarised
relays.
Having connected the apparatus as shewn in Fig. 1, the adjustment is effected in
the following manner:-
(1st.) Both stations make the resistance of the shunts R, B, and R, Bo, equal to
about / or /, the approximate resistance of the line and the distance station's
apparatus.
2nd. One station, say "the "up," then slides the loose wire attached to K along
R, B, until a point is found at which making and breaking contact with earth by
means of K has no effect on the deflection of G's needle; at this point the travelling
peg is firmly inserted. The other station now does likewise, and finds the correct
position for the wire attached to Ko.
3rd. Each station now sends letters or words for the other to adjust the relay.
This is done in the same way as for single working and need not therefore be fully
described. The apparatus at each station is now ready and signals can be
transmitted simultaneously from both ends by working the levers K and Ko up
and down in the usual manner.
The action of the apparatus may be briefly described as follows:-When both
keys are at rest the currents from B and Bo flow through the system, R and Ro
become electro-magnets and attract their respective armatures, and with them the
levers against the contacts Co. Let K be depressed to make a signal, the relay R
will not be affected thereby, but as the greater part of the current from B is now
diverted to earth, via R, B, and K, and via R, G, and K, the attractive power of Ro
becomes less than the pulling power of the spring So, the lever therefore is drawn
against C and closes the local circuit, upon which the signal begins to be formed by
the recording instrument Mo. When K is raised after making the signal the
current from B again entirely flows out to line, and the relay Ro is now able to
draw back the lever to its first position against Co, thus breaking the local circuit
and terminating the signal. A like effect is produced on R by working Ko,
Ro remaining quiescent. When both keys are working at the same time R
responds to Ko and Ro to K, without interfering in any way with each other's
action.
The improved system possesses many advantages generally speaking over existing
methods. The following are the most important:-
1st. The batteries here take the place of artificial lines at each end, and con-
sequently rheostats are dispensed with.
2nd. Sets of condensers or induction electro-magnets, or both, are not required,
for there is no appreciable return current.
3rd. Since the currents from both ends combine to actuate the relays only half
the battery power necessary in other methods is here required, and unlike other
methods, where about half the current only goes to line, the whole of the current
here generated is effective.
(4.) No special sort of key or transmitter is necessary.
(5.) An artificial resistance between the front contact of the key and earth is not
required, except for very delicate experiments, for since the internal resistance of
the battery is so small when compared to the resistance of the line and the distant
station's apparatus, the strength of the signals is practically the same in both
positions of the lever,

page_text: (6.) In short, with the single exception of a rheostat which most telegraph stations
possess, no special apparatus whatever is required. It is true the use of the improved
relay is recommended, because of the more delicate adjustment it is susceptible of,
but it must be a very bad line indeed on which the improved method will not work
well with ordinary sensitive relays. My duplex telegraph therefore compares most
favourably with other systems by reason of its extreme simplicity, and the ease and
rapidity with which it can be adjusted.
I will now describe the second part of the Invention, which relates to improve-
ments whereby the ordinary unpolarised relays or electro-magnets is rendered
susceptible of great sensibility, both for duplex and for single transmission. This is
done for duplex by so utilising the local current which the working of the relay
brings into play at certain times, that the armature at these times is itself an
electro-magnet and opposes the attraction subsisting between its poles and those of
the coils to the pulling force of the springs, so that if need be the magnetism of the
coils has only to overcome the inertia of the lever and not the force of the spring as
well;
and for single working by making the counteracting springs parts of the
local battery circuits and placing within them cylindrical bar-imagnets or bars of
soft iron.
Fig. 2 shews by a side view the general arrangements; R is one coil of the
electro-magnet; L, Lo, is a light brass lever supported at A and carrying a light soft
iron armature N; C, Co, are adjustable contact screws to regulate the play and
position of the lever. They are insulated from each other and from the rest of the
instrument. D is an adjustable spring made of insulated wire to draw back the
lever. Within the spring is placed a bar-magnet or piece of soft iron (see Fig. 4);
B is the local battery, and M the recording instrument.
Fig. 3 shews a front view of the armature and lever; the latter consists of two
parts Land Lo (see Fig. 2), insulated from each other by a thin strip of (say)
ebonite. The little connecting screws 1 and 2 are insulated from the half of the
lever Lo, and those marked 3, 4, from the half L. To screw 1 is connected one end
of the spring D. The armature is a light cylinder of soft iron hollow throughout,
but solid at the ends and shaped as in Fig. 3; round the narrow part a few layers
of insulated copper wire are wound, one end of this wire is connected to screw
1 or 2, the other end to screw 3 or 4. Now if the relay be required for duplex
working, one pole of the local battery is connected to Lo, and the other pole through
M to the contact C, the local circuit is therefore completed through the armature
coil whenever the lever touches C. So long as the distant station's key is not
pressed down, the lever is held against Co, the local circuit is open, and the
armature N, S, behaves simply as soft iron, but when the distant key is depressed
the lever is drawn against C by the full force of the spring. The local circuit is now
closed and the armature becomes an electro-magnet, the current being so directed
through its surrounding wire that its N and S are opposite to the S and N poles.
respectively of the coils. The new attraction now subsisting between the latter and
the armature, may be regulated so as to counterbalance any desired fraction of the
pulling force of the spring, so that when the coils regain their original power it has
only if need be to overcome the inertia of the lever which is so poised as to move
with a slight increase of magnetic force.
Either the armature may be a perfect cylinder that is not slit or divided along its
length, or a small adjustable electro-magnet coil or "shunt" may be inserted
between the ends of the copper wire. In both cases, the armature retains its
polarity for a moment after the local circuit is broken and thus continues to aid tho
attractive power of the coils. The attractive influence of the armature while au
electro-magnet can be regulated in one or more of the following ways.
1st. By tightening the spring D.
(2.) By varying the strength of the local current by adding to or taking from the
number of cells or by modifying their arrangement.
3. By varying the distance between the armature and the coils by means of the
screws C and Co.

page_text: (4.) By inserting an adjustable shunt between the ends of the copper wire. This
arrangement of relay is therefore peculiarly adapted for the improved duplex
system, for it can be worked by a small rise and fall of the magnetism of the coils.
When it is desired to resort to single working the following changes must be
made in the connection of the apparatus at each end. The pegs must be removed
from E and Eo, the commutator pegs transferred to the holes between the blocks
marked 1 and 3. One pole of the local battery is shifted from Lo to the free end
of D, and the other pole C to Co. The apparatus is now ready for single working,
the pegs K1 and K 2 being used in place of K and Ko.
When the distant station's key is depressed the current from that station flows
through the line and through the relay R, whereupon the lever is attached and
touches the contact Co, thus closing the local circuit. The local current now
circulating in the spring D causes each coil to attract its neighbours; this shortens
the spring and therefore increases its tension or pulling force, so that when the
distant key is raised the lever is sharply pulled back, this enables me to weaken
the force of the spring and consequently to work with weaker currents.
The attraction between the coils of the spring can be most readily regulated as
follows 1st, by varying the length of the magnet or soft iron bar enveloped by
the spring; or, 2, by varying the power of the local battery in the manner herein-
before described; or, 3, by altering the tension of the spring itself. Of course only
one battery is used at a time for single working, but the effect on the distant relay
is almost the same as in duplex working, for the resistance in circuit being less, the
current is stronger and again the whole of this current goes through the relay, the
shunt circuit R, B, being interrupted.
The improved relay is also applicable for single working where reversed induction
or momentary battery currents are employed. For this it is only necessary to
direct the local current through the armature coil in such a manner that the N and
S poles of the armature are opposite to the S and N poles respectively of the coils,
while a working current is being sent, and consequently to the coils N and S poles
while a reversed or spacing current is flowing. Now suppose a momentary working
current is sent, the lever is attracted to Co, the local circuit is closed, and the
armature becomes an electro-magnet. After the working current ceases and until
the arrival of the reversed current the armature is held in position by its attraction
for the cores of the coils. When a reversed current is now sent the armature is
repelled by the polarity of the coils, and this repulsion added to the force of the
spring sends the lever against C and breaks the local circuit.
It may be well to mention that if polarized relays are used with the herein.
before described duplex system, care must be taken that they are so joined up that
the current throws the tongues against the insulated stops. The tongues must be so
adjusted as to rest against the contact stops when no current is flowing.