IMPROVE- MENTS IN ELECTRIC TELEGRAPH APPARATUS
Year: 1861

page_text: PROVISIONAL SPECIFICATION left by John Clark at the Office of the
Commissioners of Patents, with his Petition, on the 12th October
1861.
I, JOHN CLARK, of Glasgow, in the County of Lanark, North Britain,
Machinist, do hereby declare the nature of the said Invention of "IMPROVE-
MENTS IN ELECTRIC TELEGRAPH APPARATUS," to be as follows, that is to say:-
This Invention comprises improvements in electric telegraph apparatus
designed to facilitate and increase the rapidity of transmission of signals or
messages.
In one modification of the improved apparatus suitable for the needle
telegraph, the transmission of signals is effected by depressing stops or keys
arranged so as to require the smallest convenient movement of the fingers to
reach any stop, similarly to the keys of a concertina for example. When the
instruments are arranged to transmit a great number of different preconcerted
signals, such as the letters of the alphabet for example, many of these have
to be made up of two or more minor signals as is well understood; in the
improved apparatus, however, the single depression of a stop is made to pro-
duce all the component actions required to make up the corresponding signal.
To effect this according to one modification, each stop spindle is formed with
metallic parts insulated from each other, and these on the depression of the
stop come in contact with stationary metal pieces communicating respectively
with the poles of the battery and one or more line wires, whilst a permanent
communication to the earth is made with certain of the metallic parts of
the spindle. Supposing, for example, that the compound signal to be trans-
mitted by one stop consists in sending a positive current, a negative current,

page_text: and a positive current in succession along the line, then on the spindle of
that stop the lowest metallic parts will be arranged so as on first depressing
the stop to put the positive pole and the line in communication, the negative
pole communicating through the spindle with the earth. As the depression
proceeds these contracts are discontinued and metallic parts a little higher
up the spindle come in contact with the stationary metal pieces, being ar-
ranged to put the negative pole in communication with the line, and the
positive pole with the earth. The spindle passing still lower brings its
highest metallic parts into action, and these being disposed like the first or
lowest, cause a positive current to pass along the line, completing the signal.
Of course the several spindles have their metallic parts disposed differently
so as to cause the transmission of different combinations of signals. The
movement of each spindle is regulated by a guide and two springs arranged
so that on descending one spring presses the spindle in contact with the
stationary pieces, whilst on reaching the lowest point the other spring forces
it to the other side of the guide, so that it returns upwards clear of the
stationary pieces. The apparatus described may also be applied to telegraphs
of the Morse class, in which case the parts may be somewhat simplified.
The details may be varied in many ways whilst still operating on the
same system. Thus the stops may each have only one set of metallic
parts which come successively in contact with two or more sets of stationary
metal pieces, or the stops may act upon ratchet barrels, fitted with one or
more repeats of the sets of metallic parts, so that when each stop is
depressed it turns its barrel to the extent of one repeat, and the metallic
parts of the barrel from the contacts as before, whilst the stop rises without
turning the barrel back, and on being depressed again shifts it round the
length of another repeat.
In another modification of the electric telegraph apparatus, the trans-
mission of signals is effected by means of a disc having marked round it
letters or other signs. A metal spindle situated in the centre of the disc,
and having a radial arm, is made to rotate at as uniform a rate as possible
by means of clock work with which it has a frictional or clutch connection.
To make a signal a metal stop is depressed at the corresponding sign and in
the path of the rotating arm, and when this arm comes round and in contact
with the stop, it completes a circuit, and so transmits a current, being
held stationary the time the stop is kept down. At the opposite end, the
current so transmitted, is contrived to act upon a magnetic armature in such
a way as to arrest a card or disc which is rotated by means of a frictional
or clutch connection at the same speed as the rotating spindle. at the

page_text: other end. The card has the signs marked round it, and when arrested, the
one designed is exhibited stationary at an aperture in a cover placed over it:
It is however preferred to have the entire card exposed, and to have above
it a stationary pointer the sign to be noted being that which is under or at
the pointer on the card's motion being arrested. On the stop at the trans-
mitting end being raised the rotation of the arm at one end and of the card
at the other is simultaneously resumed. This method of indicating signs
may be combined with some of the arrangements described in the first
modification. To provide against the rotating parts at opposite ends of the
wire or cable getting too far out of correspondence, a signal specially marked
for the purpose may be transmitted at intervals either by hand or by clock-
work in such a way that the attendant at the receiving end may know, from
previous arrangement, what signal he should receive, and may easily shift
round his card (which is only driven by friction) or the stationary pointer or
cover to the correct position, should the sign indicated not be the right one.
The motion of the clockwork at both ends is by preference regulated by
vibrating pendulums connected with the rest of the works by cranks con-
trived to dispense with the intermittent motion of the ordinary escapement.
Minute inaccuracies in the motion of the indicating card may be corrected
automatically by forming the circumference of the card with ratchet teeth,
or with teeth having inclined sides, there being one tooth for each sign space.
The motion of this card is arrested by the inward movement of a counterpart
tooth, which enters between the card teeth, and by acting on their sides forces
the card into correct position, provided it has not deviated therefrom more
than half a tooth or division. A greater deviation must be corrected by the
adjustment already indicated.
The movement which arrests the card may be contrived to move it out of
contact or out of gear from the frictional or clutch surface which drives it,
and to move it against stationary teeth or projections which arrest its motion,
and by a wedge action correct slight inaccuracies in its position, in the
manner described with reference to the moveable arresting tooth.
In a modification of the apparatus last described provision is made in the
receiving instrument for retaining a number of successive signals in view
for a limited time. A number of indicating discs are mounted on a wheel or
frame with their planes disposed radially round an axis, and the signs are
marked on their circumferential edges, or instead of signs, printing types
or markers may be fixed or formed on their edges. Provision is made at
the sending instrument to pass a current at the commencement of each re-
volution of the rotating arm, which current has the effect, with or without

page_text: the aid of clockwork, of shifting round the frame of indicating dises the extent
of one disc. This brings each disc in, succession into a position where it is
made to rotate on its own axis by clockwork at the same speed as the rotating
arm at the sending end. Then by arrangements like those described in the
preceding modification it is stopped with the sign to be indicated in the posi--
tion for being indicated. The frame. is next shifted and the next disc is
rotated and stopped at the next sign, and so on, the discs being successively
turned to indicate the successive signs composing the message or part of. it.
Provision is made for restoring the discs in succession to their starting positions
just before they come round again to the position wherein they are acted
upon. With this arrangement nearly as many signs may be kept in view
as there are discs round the frame, and if the discs are formed with types
or markers they may be made to give off one or more impressions by being
carried in contact with receiving surfaces through the.gradual rotation of the
frame which carries them.