IM- PROVEMENTS IN ELECTRIC TELEGRAPHS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Johann Carl Ludwig Loeffler and
Richard William Henry Paget Higgs at the Office of the Commissioners of
Patents on the 18th November 1876.
JOHANN CARL LUDWIG LOEFFLER, and RICHARD WILLIAM HENRY PAGET HIGGS,
both of No. 12, Queen Anne's Gate, Westminster, in the County of Middlesex. " IM-
PROVEMENTS IN ELECTRIC TELEGRAPHS."
In signalling by electric telegraph over land lines or cables of considerable length
the impulses sent from the one end of the line arrive at the other end in such a
manner that when they are caused to succeed each other rapidly they are apt to
produce signals running into one another or otherwise indistinct, or to fail to produce
signals, and thus the rapidity of transmission is limited. Various means are applied
for remedying this defect with a view to obtain greater distinctness of signals, and
permit greater rapidity of transmitting them.
Our Invention relates to a method of operating and arranging connections and
appliances for this purpose.
By means of a bridge arrangement of suitably regulated resistances we place the
receiving instrument under a definite difference of potential derived from a battery'
or other source of electricity placed at the receiving station in the battery branch of
the bridge arrangement, but so that the instrument does not operate for signalling
except when this difference of potential is varied by an impulse caused by action at
the sending station.
The arrangement for this purpose may be varied; one such arrangement is shewn
diagrammatically at Fig. 1 of the accompanying Drawings, and is of the following
character:-The line or cable L is connected to the one terminal of the receiving
instrument I, and also through a resistance R permanently to one pole of a
battery B or other source of electricity, the other pole of which is connected to earth
at E. The first named pole of B is connected through a resistance S to the other
terminal of the instrument I, which is also connected through a resistance T to
earth. The resistances R, S, T, are so adjusted to each other, and to the battery
power, and also to the resistance of the line while the standing instrument is
quiscent as to bias the receiving instrument to such an extent that when impulses
are transmitted from the sending station, either the instrument will not be acted
on by the beginning and ending portions of those impulses, during which portions
the force gradually increases and decreases, or that so much force will be added

page_text: to these portions of the impulses that the receiving instrument will begin to be
influenced nearly at the beginning, and continue to be influenced nearly up to the
termination of each impulse.
When applying our arrangement to a line having considerable capacity, such as a
cable, we sometimes connect to the branch S a condenser or combination of con-
densers as shewn at C in the diagram Fig. 2. For the condensers may be substituted
equivalent electro-magnets; a bridge arrangement of like kind may be employed
without a separate battery in the manner shewn diagrammatically at Fig. 3. In
this case the resistance branches R and S are at their junction connected to earth E,
and a condenser or combination of condensers C is introduced in the branch S.
In the arrangement shewn in Figs. 1 and 2 the instrument I and the battery B
may change places, and in the arrangement shewn in Fig. 3 the instrument I may
be transferred to the branch b, the resistances being suitably adjusted.
Arrangements such as we have described may be employed in combination
with other known arrangements for the same purpose, and condensers, induction
coils, electro-magnets, batteries, and other known appliances may be introduced in
the several circuits.
A bridge arrangement somewhat similar to that described above has been
employed for duplex telegraphing, but in that case it is applied for the purpose
of preventing the receiving instrument from acting under the influence of signalling
currents transmitted from the receiving end of the line, and consequently the
resistances and connections are arranged to maintain different electrical conditions.
In the bridge arrangements above described any receiving instrument of known
construction may be employed. We prefer however to use an instrument similar
in some respects to that described in the Specification of a Patent granted to
C. W. Siemens on the 25th June 1872, No. 1919, and shewn in Figs. 9, 10, and 11,
of the Drawings annexed to the said Specification. Instead of employing a single
coil mounted on an axis, as shewn in these Figures, we divide the coil into two equal
parts and place them opposite to one another, connecting them together by a cross
bar or frame, and suspending the whole by one or more wires or fibres. The coils
thus suspended in balance are caused to take an angular position to either hand by
the passage of electrical currents through them, and are brought back to their
position of rest when the disturbing influence ceases, and these angular movements
of the coils may be utilised in any known manner for signalling, or for making
or breaking contact for another circuit. Instead of using two equal coils in this
manner, a single coil with a counterbalance may be mounted as above described.
In the visible signals of the Morse and other like codes, the dots, dashes, or other
marks employed to constitute by their various successions and combinations different
letters or other signals are separated by blank intervals, or in some kinds of instru-
ments, as for instance the syphon recorder, by certain marks indicative merely of
separation. The production of each such blank, interval, or separation mark
occupies a portion of time which may be considered to be lost for the purpose of
signalling. In order to avoid this loss of time we produce the compound marks
constituting signals by reversals of current or changes of potential immediately
succeeding each other, in such a manner that each current or change of potential,
or each combination of currents producing one change of potential at the receiving
station is utilised for the production of a significant signal, and that these signals are
distinguished from each other notwithstanding their immediate succession. For
this purpose we produce the marks alternately in two parallel lines, so that no
interval of space longitudinally is required between them, and no appreciable
interval of time is occupied in passing from one mark to the next in order. The
signals formed in this manner may be considered merely as combinations of dots
and dashes irrespective of the particular line on which these present themselves.
Thus for the letter B, which according to the Morse code consists of a dash followed
by three dots, as shewn at Fig. 4, the same combination of marks produced
according to our system without intervening spaces may present itself, as shewn at
Fig. 5, or as shewn at Fig. 6, no regard being paid to the position of the marks in

page_text: the one or the other of the two lines. But by arranging the code employed so that
regard is had to the position laterally of the several marks constituting a letter or
signal, we are enabled to double the number of available distinct signals, and can
consequently select for those most generally used such of the combinations as
consist of the least number of marks, or as can be most rapidly produced.
According to this mode of operating, the signals shewn in Figs. 5 and 6 would
be treated as two distinct signals, regard being paid to the particular line on which
each of their constituent marks presents itself.
In order that this may be more clearly understood, as well as the features in
which signals of the kind described are distinguished from those of the ordinary codes,
we have shewn at Fig. 7 the alphabet according to the Morse system, at Fig. 8 the
same alphabet according to what is known as the Steinheil code, in which dots in a
separate line are substituted for dashes.
In Fig. 9 we have shewn an alphabet composed according to our improved
method having no intervals between the successive marks constituting each letter,
and without regard to the particular line in which these marks occur, and at Fig. 10
we have shewn a code for the alphabet consisting of fewer combinations which can
be selected when the position of each mark in one or other of the two lines is
taken into account. Not only may dots and dashes be thus combined, but also dots
and dashes, or dots alone may be combined with longitudinal spaces of equal
or varying lengths, themselves representing constituent parts of a letter or other
signals.
At Fig. 11 we have shewn such a code for the alphabet consisting of combi-
nations of dots, dashes, and spaces, each of the latter being of the length of a dot,
and occuring only when marks follow each other in the same line.
At Fig. 12 we have shewn a code consisting of dots combined with spaces
employed only when dots follow each other on the same line, and at Fig. 13 a code
consisting of dots combined with spaces, each having the length of a dot and
occurring whether the dots follow each other in the same or in alternate lines.
It is obvious that other combinations might be employed, as for example, dots, or
dots and dashes combined with the spaces of various lengths, but we prefer the
combination of dots and dashes without intervals, as shewn at Figs. 9 and 10, as we
can then employ a very short blank interval to indicate the separation of one letter
from another, preventing also the possibility of any two constituent parts of a letter
running into one another.
For producing marks on two lines as above described, various instruments having
double styles may be employed; Fig. 14 shews diagrammatically an arrangement
of a chemical writing instrument for this purpose; p is the strip of prepared paper
passing over the roller ; a and bare two styles, the one connected to the line 1, and
the other to the earth e.
When a positive current arrives by the line, one of the styles a or b is caused to
mark the paper, and when a negative current arrives the other style is caused to
mark the circuit to or from earth, being in both cases completed across the paper,
which may simply have its surface moistened with sensitizing solution by being
passed over a sponge or other porous body charged with solution before it reaches
the styles.
Instead of employing positive and negative currents, similar effects may be
produced by a rise and fall of potential in the line.
Although we have above described our improvements in telegraphic signal codes
as applied in the case where visible marks are produced, it may be readily under-
stood that a similar system can be applied for simplifying and abbreviating signals
given by deflections of needles or movements of beams of light, or by sounds of
different tone by dispensing with the-blank-intervals or their equivalents usually
presented and making the indications follow each other in close succession.