IMPROVEMENTS IN ELECTRO-TELEGRAPHIC INSTRUMENTS
Year: 1868

page_text: PROVISIONAL SPECIFICATION left. by William Alexander Lyttle at
the Office of the Commissioners of Patents, with his Petition, on
the 26th October 1868.
I, WILLIAM ALEXANDER LYTTLE, of the General Post Office, London,
in the County of Middlesex, Civil Engineer, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN ELECTRO-TELEGRAPHIC
INSTRUMENTS;" to be as follows:-
I arrange a straight row of lever keys to represent the letters of the
alphabet or other desired signs, and I place a drum or cylinder in such
a position that when the keys are depressed their ends shall touch or
approach the surface of the cylinder in the same longitudinal line. This
cylinder is fitted with the same number of projecting pins as there are
keys, and the pins are distributed spirally from one end of the cylinder
to the other, so that lines drawn parallel to the axis through each pin
should divide the surface of the cylinder into as many equal longitudinal
parts as there are keys. This drum I call the "stop drum."
end of the cylinder I arrange a train of clockwork to propel the cylinder
in the required direction, and I adapt the clockwo: k either with a spring

page_text: or weight as a "maintaining power," to be wound up either with a key
or by means of a treddle or crank. The depression of the treddle or
crank unwinds a cord or chain from the drum which is actuated by
the "maintaining power," and the latter is thus wound up. As the
apparatus works the treddle or crank ascends, and when it nearly reaches
its highest point it or the weight when a weight is used should strike a
click or other alarm to cause the operator to again depress the treddle or
crank. In a plane at right angles to the plane of the keyboard there is
a bar which presses forward by means of a spring against those ends of
the keys which stand outward furthest from the stop drum. The upper
edge of this bar next the keys is flanched inwards, so as to engage in a
notch in the outward end of the key when the latter is depressed. The
outward end of each key is pressed upward by a separate spring, or it is
weighted at the end, so as to gravitate into the proper position clear of
the flanched bar. When the key representing the letter A is depressed
the aforesaid flanched bar clicks into the notch in the end of the key.
If now any other key is depressed the flanched bar is driven back by
such key out of the notch in the A key, and the latter springs up, whilst
at the same time the stop drum revolves till it is stopped by the proper
pin striking against the end of the key last depressed. The notched
or outward end of the keys should be bevelled, so as to enable them
when depressed to slide latch-like behind the flanched bar till it clicks
into the notch, which enables this bar to hold the key. By this means
the depression of any one key will liberate all others which may then be
down by pushing out in its wedge-like action the flanched bar which fits
into their notches. At one end of the cylinder, or moving in any other
position simultaneously with it, is the arrangement, either magneto-
electric or voltaic, by means of which the rotation of the stop drum
between any two stops shall cause as many electric impulses as there
are intervening keys. These impulses pass through any suitable re-
ceiving dial instruments constructed on the "pointer or "step-by-
step" principle; such, for instance, as those known as Wheatstone's or
Siemens's, and in this way the revolution of the drum to any particular
stop will cause the pointer instrument at the distant station to indicate
the letter or sign represented by the key depressed. The electrical
current employed may be either magneto-electric or voltaic. In the
latter case I employ any suitable contact breaker for sending nume-
rically regulated intermittent currents, either in one or both electrical
directions.
"

page_text: The contact breaker which I prefer for this instrument is made
thus The " stop drum moves a spur or other wheel which
engages into a pinion, and the relative diameters of the two are such
that one revolution of the larger causes as many half revolutions of the
smaller as there are keys. On one side of the pinion is fitted eccen-
trically a pin which works in a slot in the end of a lever, and causes
this lever to oscillate, and so to make contact at each half revolution
against one or other of two prongs of a forked conductor.
I also employ the following modification of this arrangement for the
purpose of printing the message at the receiving station. A disc is
made to revolve by any convenient maintaining or propelling power,
subject, however, to the action of an electro-magnetic escapement of any
of the well known forms, which is worked by the currents sent from
the transmitting station with or without the intervention of a relay or
"induction coil." On one side of this disc I place a number of thin
flat springs radiating from the centre, and having at the end of each
a type representing a letter of the alphabet or other sign, the face of the
type being turned towards the disc and projecting slightly through a
hole cut for the purpose through the disc near its circumference. These
types are like hammer heads attached to the radial springs, and a gentle
pressure will cause cach head to pass through its hole in the disc and
imprint, if inked, an impression of its letter or other sign on any surface
which may be close to the disc on the other side. These types are
limited by the disc to one uniform range of backward play, and are
inked by contact with an inking roller, or they simply make dry pressure
on tinfoil, or on carbonic or other prepared paper or textile tissue. The
latter should convey the impression to the white paper which is placed
underneath. The white paper printing surface with or without carbonic
medium is secured by a pair of india-rubber bands, one being at each
end, around a cylinder, or fastened in any other convenient manner,
and the cylinder is made to rotate on a screw axle in such a way that as
each letter is printed by the depression of one of the disc types, the
cylinder is advanced forward the space necessary to make room for the
next letter, and one complete revolution will by reason of the screw
axle advance the cylinder in the direction of its axis far enough to leave
room for the printing of the next spiral line of message. This spacing
or forward ratchet movement is precisely the same as that adopted, with
trifling modifications, in Dujardine's, Hughes's, and most of the other

page_text: Roman type-printing telegraphs, and is actuated by the electro-magnet
which depresses the printing type in the disc. The spacing ratchet
wheel for this purpose should be connected with the cylinder by two
friction or india-rubber tired wheels, one of which is for slow and the
other for faster motion, and cach acting on similar wheel rims, pro-
portioned for the object in view, on the end of the printing cylinder.
The pair working together for slow motion should have their edges cut
away at one point, so as not to engage cach other when the cylinder is
passing its paper wrapper from the end of one line to the beginning of
the next, and at this point only should the pair of fast wheels come in
contact. By this means a single tooth of the ratchet which advances
the cylinder by the slow wheels only the space of one letter, will, by
the action of the fast wheels at the proper point, carry the cylinder past
the joined edges of the sheet of paper on which the printing is effected.
commencement.
The depression of the printing type is effected as follows:-Suppose
the printing disc is standing at zero, and that I wish to transmit and
print the letter H, I accordingly depress the H key on the transmitting
instrument, and the stop drum advancing sends eight currents, which
must be in one direction only, to the receiving station. These currents
produce eight movements of the printing disc escapement, and as the
disc revolves in the reverse direction to the order in which the letter
types are arranged the H type will now stand where the zero was at the
The reverse curent is now sent along the wire, and
owing to the under-mentioned arrangement it exercises no attraction on
the escapement armature, whilst it attracts with or without the inter-
vention of a relay the lever by which the H type is struck against the
paper on the aforesaid cylinder; so on for each letter forming the words
to be printed, and there is one blank in the printing disc by means of
which to space the separate words. The first or "step-by-step" current
passes through all the electro-magnets, but the above effect is thus
produced. A permanent magnet is bent at right angles, and on one
of its poles, say, the north, the iron lever of the escapement plays in a
plane parallel to the other half of the magnet. Attached at right angles
to the same pole of the magnet and in the same plane as the escapement
lever is a fixed bar of soft iron coiled round with the transmitting wire
which carries the message. When no current passes the soft iron core
of this electro-magnet will have the same polarity as the iron (or steel)
escapement lever, and the latter will thus be repelled; with or without
'

page_text: the aid of a spring, whilst it will at the same time be attracted by the
adjacent iron core of an electro-magnet standing on the south pole of
the rectangular permanent magnet. The latter electro-magnet gives
passage also to the message current, but in such a way that when the
current passes its polarity shall be reversed, and the same result should
follow in the case of the electro-magnet on the other side of the escape-
ment lever. Thus when there is no current the escapement lever is
repelled by one electro-magnet core and attracted by the other, whilst
when the message or first current passes the reverse attraction takes place.
When, however, the reverse or printing current is sent it is obvious that
the natural magnetism of these cores will only be strengthened, and that
the escapement lever will not be moved. By an almost exactly similar
arrangement the printing current moves the lever armature which
presses against the type in the disc wheel whilst this lever is not
attracted by the first or message current.
The transmission of the reverse or printing current is effected by.
special reotrope keys, the ends of which on striking against the stops of
the stop drum transmit the required reverse current. Thus the lever.
of the aforesaid eccentric contact breaker may at each contact connect
the positive pole of the battery with the line and the negative with the
carth, whilst the key depressed shall when struck by the stop send the
reverse current. To do so the key may, like the eccentric contact lever,
carry two insulated conductors, the points of which shall communicate
with a double stop pin, one-half of which shall communicate with the
proper battery pole, and the other half with earth.
In carrying out the principle of limiting by the depression of keys the
revolution of the transmitter and equalising the number of momentary
currents sent within any equal portions of such revolution, it may be found
that one of the following arrangements will answer best. In these the
currents sent along the line are those which are developed in the secondary
wire of a Rhumkorff induction coil on the breach of contact in the primary
conductor. Over and close to the soft iron core of such an induction
coil is placed a lever, one end of which engages into a ratchet by which
the stop drum is propelled. When this lever is not attracted by the
primary conductor of the coil it is raised by a spring, which thus causes
it to make contact and complete the circuit of this primary conductor.
The lever is thus attracted and in its downward motion it advances the
ratchet of the stop drum one tooth, and also by breaking the contact of

page_text: :-
the primary conductor sends a secondary induced current along the line.
When the pin of the stop drum advances to the end of the particular
key depressed the action of the coil is stopped either by the key and
stop pin making "short circuit," or by the following means, namely:-
Two levers are attracted by the core of the induction coil. One of them,
which as stated, actuates the ratchet of the stop drum, leads to one pole
of the battery, and serves to make and break contact, and the second
lever when attracted causes the moveable piece of metal against which
the first lever makes contact to press against the first lever throughout
the greater part of its movement when attracted by the coil. It is
detached only by the action of intercepting projections at the sides, and
at this moment the induction current is liberated. The ends of the
secondary wire may, if desired, be connected by two branch wires to
these contact levers so as to "short circuit" the current induced at
making contact in the primary wire. The two levers should have
between them a feeble spring, sufficiently strong however to keep them
apart till the first or ratchet lever has made its complete return stroke
under the force of its recovering spring. At this point it presses again
against the second lever. Contact is thus again made and the two levers
descend together, during which time till the contact is broken the
current will flow in the primary wire of the coil. By this means a good
steady stroke is obtained for the movement of the ratchet, and the
breaks of contact are limited with certainty to the number of ratchet
teeth moved.
It is evident that with such an arrangement it will be possible on
liberating all the keys to convert the transmitting drum into a substitute
for the "pointer," either by means of a dial at the end or by a circular
strip at the middle of the drum, one of the letters or figures on which
can be seen through a hole provided for the purpose each time the
message current stops at that letter or figure. To effect this double
purpose it will be necessary to provide a suitable switch by which the
aforesaid connexion between the battery and primary coil shall only be
completed by the action of a "relay," which shall by the same switch
be placed between the line and earth. This switch should also serve to
cut off the connexion between the secondary wire of the induction coil
and the line. By this means the printing disc herein-before described
may be propelled if desired without any other maintaining power.
this case, whether a maintaining power is used or not, it will perhaps be
In

page_text: found necessary to connect the several electro-magnets of the escape-
ment and printing lever with a local battery by means of a double
polarized 'relay," one armature of which shall be attracted by the
message current, and the other connected with the printing lever magnet
by the reverse current only. The arrangement of the relay magnets'
should be exactly similar to that of the magnets to which they are.
attached; that is, if the escapement armature is arranged to act with a
positivo current only its relay should act only when such current is sent
on the line wire.
When induced currents are sent by the stop drum for the purpose of
printing, as I have herein-before specified, it may be found necessary to
have a special coil for the transmission of the reverse or printing current,
and in that case the drum need not have double stop pins, the key and
single pin being sufficient to complete the contact. Each key may be
armed by a slight spring at the end, so that contact with the pin shall
occur at the moment of impact, and then be broken by the spring
leaping across the point or side of the pin..
A circular dial will answer all the purposes of the stop drum in all
these arrangements, and the keys may be placed in a circle, as 'in
Wheatstone's "A, B, C" dial, with Wheatstone's well-known chain
passing under the keys so so as to prevent the depression of more than one
key at a time. The end of each key should raise a pin through the dial
on depression, and against this pin the hand would be stopped, and with
it the ratchet or other connexion by which the hand is moved, as in the
case of the stop drum already described. By releasing all the keys this
dial would under the same conditions as the stop drum be convertible
into a receiving as well as a transmitting instrument. Its hand would
serve to make the contact required for transmission of the reverse
currents when the message sent is to be printed at the distant station.
In order to enable currents to be transmitted with facility from
any one of a circle of offices to any other office of the same circle I
employ the following arrangement, which I designate the "universal
switch." An annular groove is cut in a piece of wood or other non-
conductor of electricity, and the inner edge of the groove is bordered by
a slightly. projecting flat ring connected with the earth. On the outer
border of this groove are any number of line terminals, from each of
which a conducting spring projects radially across the groove and presses
against the under surface of the earth ring on the inner edge of the

page_text: groove. Whilst this contact continues it is obvious that any current
arriving will be carried to carth. In the centre of the earth ring and
insulated from it stand two hands, cach of which carrics a knuckle-
jointed lever about midway, and acting like the blade of a pocket knife,
the object being that upon the hands being pointed to particular ter-
minals the raising of the knuckle levers shall press against the spring
conductors underneath them which connect the terminals with the earth
ring, and so break this connexion. Suppose, for instance, that Fairfield
office wishes to speak to Stockport office through Manchester, the Man-
chester office on receiving the arranged signal turns one hand to the
Stockport terminal and the other hand to Fairfield, then on raising the
levers of the two hands the current from Fairfield instead of going to
earth passes from one hand to the other, and on to Stockport.. If the
hands are insulated from cach other, the current arriving by one hand
may forward through the other by passing through a local "relay."
When the distances are short this relay can be cut off by any simple
"short circuiting" junction, and the current will go on direct. Onc
terminal should be connected with the instruments at the office where
the switch stands in order to receive or transmit messages, or if the office
instrument is placed in the circuit between the two hands, one of the
hands should be marked "earth," and there should be an earth terminal
and spring in order that the earth and line may be placed respectively on
the proper sides of the instrument.
1
A
I adopt as follows an exactly similar arrangement in the case of the
testing board or box for trying the electrical state of the lines. I have
two or more parallel rows of terminals, each opposite pair being con-
nected with the same line wire, and with cach other by a flat spring
precisely as the earth ring and terminals are in the universal switch.
galvanometer sliding on fixed guide rods can be passed at pleasure along
between the connected rows of terminals, and when on one side it makes
connexion with, a particular terminal by the friction of a projecting
spring it breaks the direct connexion between the terminals by pressing
against and so forcing back the flat terminal connecting spring. The
points of the contact thus first made by the galvanometer on its being
advanced along the guides place it in circuit without for one moment
interrupting the line, and by this means I avoid breaking the continuity
of a line for testing purposes, when I see that a current is passing at the
time. If, however, no current is evinced a plug or other connexion

page_text: between two terminals attached to the galvanometer is withdrawn,
and the circuit of the latter being thus broken one or both of its
terminals or or of the terminals between which it stands may be placed
in connexion with the testing instrument.