IMPROVEMENTS IN ELECTRICAL STEP-BY-STEP INSTRUMENTS and Apparatus FOR GIVING AND RECEIVING TELEGRAPHIC MESSAGES, AND FOR COMMUNICATING SIGNALS AND CONTROLLING POINT AND SIGNAL APPARATUS ON RAILWAYS, ALSO PARTLY APPLICABLE TO OTHER SIGNALLING PURPOSES.
Year: 1872

page_text: LETTERS PATENT to Carl Heinrich Siemens, of No. 3, Great George
Street, Westminster, in the County of Middlesex, Civil Engineer, for
the Invention of "IMPROVEMENTS IN ELECTRICAL STEP-BY-STEP INSTRUMENTS
and Apparatus FOR GIVING AND RECEIVING TELEGRAPHIC MESSAGES, AND FOR
COMMUNICATING SIGNALS AND CONTROLLING POINT AND SIGNAL APPARATUS ON
RAILWAYS, ALSO PARTLY APPLICABLE TO OTHER SIGNALLING PURPOSES.”.
Partly a communication from abroad by Dr. Werner Siemens,
of Berlin, in the Empire of Germany.
-
PROVISIONAL SPECIFICATION left by the said Carl Heinrich Siemens
at the Office of the Commissioners of Patents, with his Petition,
on the 3rd October 1872.
I, CARL HEINRICH SIEMENS, of No. 8, Great George, Westminster,
3 in the County of Middlesex, Civil Engineer, do hereby declare.
the nature of the said Invention for "IMPROVEMENTS IN ELECTRICAL
STEP-BY-STEP INSTRUCIENTS AND APPARATUS FOR GIVING AND RECEIVING
TELEGRAPHIC MESSAGES, AND FOR COMMUNICATING SIGNALS AND CONTROLLING POINT

page_text: AND SIGNAL APPARATUS ON RAILWAYS, ALSO PARTLY APPLICABLE TO OTHER
SIGNALLING PURPOSES," to be as follows :—
This Invention relates to improvements in the construction and
working of alphabetical dial telegraph instruments, whereby messages
are transmitted, received, and printed by means of electricity, and also i
of electrical signalling instruments and apparatus to be used chiefly on
railways for the purpose of guiding and controlling the traffic, and the
working of points, signals, and similar apparatus.
The electrical step-by-step instruments ordinarily used for giving and
receiving telegraphic messages have at each end or station of the 1
telegraph line two dials, one for the use of the operator in transmitting
a message, and the other on which is indicated the message received.
One part of the present Invention relates to the combination of these
two dials in one instrument so that one dial at a station surrounded by
its finger keys serves both to indicate to the transmitter what message 1
he is sending and also to indicate a message received. For this purpose
a horizontal shaft or spindle is provided with a winch handle, or pre-
ferably with two winch handles, one at either end, so that the operator
can use either his right or his left hand to work the same. On this shaft
is a wheel which gears with a pinion on the revolving armature, which
preferably, is of the kind known as "Siemens' cylindrical armature,"
and which rotates between the poles of a suitable set of permanent
magnets. The dial being made with 26 divisions, the shaft is geared to
the armature, so that the latter makes 13 whole turns or 26 half turns
to two of the shaft, and thus causes 13 positive and 13 negative:
alternating currents to be transmitted through the conductor. On the
same shaft is fixed a bevil pinion which gears into a bevil wheel of double
the number of teeth fixed on a vertical spindle, which spindle therefore
turns once while the horizontal shaft turns twice. On the vertical
spindle is fixed a disc wheel from the face of which project 13 pins or
teeth. On the same spindle, but loosely fitted thereto, is mounted a
lever or arm having a spring pawl which engages with the pins or teeth
of the disc wheel. This pawl has a tail projecting from it in such
a manner that when by the movement imparted to it by the disc wheel
it is brought round till this tail meets an obstacle, the pawl is thrown out;
of gear, and the disc wheel thereafter can revolve without carrying the
pawl arm with it. The effect of thus stopping the arm is that another
commutating arm tending to move with it by frictional contact in

page_text: opposition to a spring, and thereby making electrical contact for
transmission, is on the stoppage of the arm brought back by the spring
so that electrical contact for transmission is broken and contact is made
for receiving a message. The obstacle which throws the pawl out of gear
is the end of any one of the rods attached to the finger keys which may
be pressed down by the finger, and which thus changes the contact at a
a point in the revolution of the arm corresponding to the position of that
finger key. During the movement of the arm through this part of its
revolution a number of alternating currents are sent, which act in the
ordinary manner on the index at the distant station, and also on the
index of the dial presented to the operator, both these indices being thus
brought round so as to correspond with the position of the key acted on.
Immediately above the mechanism just described is situated the
indicating dial with the finger keys surrounding it. Each of those
keys has a rod projecting downwards, and is kept up by a spring;
when up its rod is clear of the pawl tail, but when depressed it forms
the obstacle which throws the pawl out of gear. Each of these rods has
also upon it an inclined latch shaped projection, which lies against a pin
or tooth projecting from a disc, which disc is kept pressed against a stop
by means of a spring. On depressing a key the inclined face of the latch
acting on the tooth or pin of the disc pushes the disc a little way round,
and when the key is quite depressed the spring causes the disc to return,
and thereby to bring its pin or tooth over the latch so as to hold the key.
down. - On afterwards depressing another key the disc being moved in
like manner releases the key formerly depressed which is then raised by
its own spring.
.A. considerable part of the apparatus as above described is of well-
known construction, but it has been necessary to describe it in order
that the points of novelty may be better understood. These points are,-
First. The arrangement which enables the transmitting keys and
apparatus to be accommodated in the same instrument with the one
dial which serves to indicate both for the transmitting and the receiving
of a message.
Second. The latch arrangement of the key rods in combination with a
spring disc, whereby any key is held down until it is released by
depressing another key.
And third. A peculiar construction of the pawl which is disengaged by

page_text: somewhat like that used for the blade of a penknife, in such a manner
that when it is out of gear the point of the pawl is kept by the spring
quite clear of the pins or teeth of the wheel, but when it is being thrown
out of gear the pressure of the pin or tooth upon it turns it a little
in opposition to the back spring, and when the pin or tooth has passed
its point the back springs throws it suddenly into its clear position.
manner:―
This Invention relates also to a means of actuating the printing
mechanism of such instruments. Usually the wheel containing the
printing types is brought round by a succession of currents step-by-step
like the index, and then an additional current is transmitted for the
purpose of effecting the impression. This additional current is a source
of inconvenience and complexity; according to the improved method
such additional current is altogether dispensed with in the following
- Between the poles of the electro-magnet is mounted the
polarized lever which works the index or type wheel, either directly or by
relay in the usual manner, and there are also mounted, side by side other
two polarized levers which vibrate in unison with the first named
polarized lever. Each of the latter two levers can be moved by the
magnetism in one direction but is stopped from moving in the other,
and the stops are so arranged that the ono moves when the other is
stopped. Between the projecting tails of these two levers is mounted a
lever which can vibrate in a plane perpendicular to the plane of the two.
levers. The tail of the one polarized lever bears against one arm of the
third lever, and the tail of the other bears against the other arm on the
opposite side of its fulcrum. Thus when the instrument is in action one
or other of the two polarized levers bearing against the third lever keeps
it in a middle position, but when the instrument ceases to operate so
that both polarized levers are left free from the magnetic influence a
spring draws the third lever out of the middle position and thereby
causes an arm on it to make contact by which the printing is effected.
Thus the mere cessation of the step-by-step process causes the printing
contact to be made.
The improvements in the step-by-step instruments for use on railways
are of the following kind:-In these instruments there are employed
indices which may be discs, semaphores, arms, or sliding frames on which
are marked known signs, or signs having predetermined meanings.
The movement of one of these indices from one position to another by
causing it to present to the eye a sign different from that which it

page_text: presented before movement gives a visible signal, and this movement
may be accompanied by the ringing of a bell or other suitable phonic
alarum. The indices are either furnished with teeth or are moved by
toothed wheels or racks provided with teeth into which engage the pallets
of an escapement similar in action to the anchor escapement employed
in clocks. This escapement is attached to or is worked by the armature
of an electro-magnet which is caused to oscillate by a number of suc-
cessive alternately positive and negative electrical currents being made
to pass through its coils. The index is loaded or counterweighted or
pressed on by a spring so as to have a bias in one direction of motion,
but being held by the pallets of the escapement when they are at rest,
it can only move in obedience to the bias tooth by tooth when the pallets
are caused to oscillate. Thus as a number of successive alternately
positive and negative electrical currents are required to give a number of
oscillations sufficient to change the signal and accidental current makes
no appreciable alteration in it.
The electro-magnets and. armatures may be of any of the known
kinds and may be combined with permanent magnets.
The electrical currents may be derived from any source of electricity
but it is preferred that they should be alternately positive and negative
as in the instruments already described.
In order to provide for moving back the index the direction of the
bias is altered by the movement of a rod, lever, or other convenient
handle, which the attendant moves and which is connected to com-
mutators so that its movement determines the line of wires through
which the clectrical currents have then to pass. The movement of this
handle while it sets the commutators also brings the weight or spring to
bear upon the index so as to overcome the bias which it previously had,
and give it a bias in the opposite direction.
As the commutators have to be arranged for the passage of either
currents sent out or currents received it is sometimes convenient for the
sake of simplicity to construct and arrange the electro-magnets which
work the indices in such a manner that one half of each, as for example,
one of the two bobbins of each magnet shall be used exclusively for the
currents sent out and the other for those received; or one half of the
coil on each of the two bobbins of a magnet may be employed for the
passage of the currents sent, and the other half for the passage of thoso

page_text: received; or the electro-magnet of cach instrument may be in duplicate,
the one being employed when currents are sent, and the other when they
are received.
In applying instruments such as are described above to block signal-
ling on railways, there are combined at each block station two
instruments one for up trains and one for down trains, and the successive
stations are connected by one wire which is sufficient for transmitting
the required electrical currents in both directions. The attendant at a
station in giving a signal from his station to another moves the handle,
which at the same time gives his own signal a bias in one direction
and sets the commutators right for the transmission of the electrical
currents and he works the magneto-clectric machine which produces
these currents.
The signals and commutators may be arranged in various ways so as
to render them suited to various systems of signalling.
In order that their operation may be understood one such arrange-
ment will now be described. The commutators being so arranged that
each instrument sends currents by the line opposite to that by which it
receives currents, and the handle which sets the commutators being
made to bias the index at its own station so as to give the block signal,
the operation is as follows:-The attendant moves the handle and thus
gives bias to his own signal, so that it will be moved to "block,” and
sets the commutators so that a current from his magneto-electric
machine shall be transmitted to the next station before him, that is to
say, the station which an approaching train has to pass before reaching
him, while he keeps the handle in the position to which he has moved
it he works the magneto-electric machine, and thus removes the
"block" signal from the station next before him and moves his own
signal to "block." The attendant at the next station beyond performs
similar operations in his turn, and thus a train going in either direction
is always signalled to stop at a station, unless the attendant at the next
station beyond has removed the block signal at the station which the
train has reached. It will be seen from the above that before any signal
can be given with the before described indices, by means of one of these
instruments, it is necessary that the operator should perform simulta-
neously two operations, viz., he must move a handle and at the same
time work the instrument for producing the electrical current.

page_text: In some cases it is desirable that the signalling index should be
capable of being moved back without moving the escapement. For
this purpose the pallets of the escapement are in such cases made
moveable, like the pawls of ratchets with suitable springs or weights
to keep them in gear with the teeth on which they operate, while those
teeth move in one direction, but to let those teeth pass them as they
move in the opposite direction.
.
In some cases. it may be desired to transmit a signal without actuating
the signal indices above described. To effect this the instrument
for producing the electric currents is provided with a contact maker
so arranged that it will pass either only the positive or only the negative
currents, and a key or commutator is placed between the line wire and
the signalling instrument above described, whereby the latter may be
cut out of the circuit and the aforesaid single current contact maker
be put in communication with the line wire to the next station on either
side, and an electro-magnet is provided through which. these currents
are passed, and the armature of which is thereby made to actuate
a bell or a visible signal distinct from the signalling instrument above
described. This electro-magnet is in the same circuit as the coils of the
said signalling instrument; but the indices of the latter are not actuated
by the aforesaid single currents as these are not alternately positive and
negative.
In combining electrical signalling instruments, such as are described
above, with the apparatus usually employed for working the points and
signals of railways; such mechanical' connections are made between
the electrical instruments and the point or signal apparatus as prevent
electrical communication, unless when the standard signal is set at
danger or the points are in a particular attidude. By these means
the electrical signal clearing the line at the previous station cannot
be given until the standard signal at the sending station has first been
put to danger, or the points there set in their proper attitude. The
block signal at the previous station cannot therefore be taken off until
the train is within the protection of the standard signals, or until the
points have been set in their proper attidude.. These connections are
of the following kind :-The lever or other handle which works a
standard. signal.or a set of points is made also to work a commutator,
which in one position of the signal or points allows the passage of
an electrical current to or from the electrical signalling apparatus at the

page_text: station, and in another position of the signal or points cuts the electrical
circuit off from the signalling instrument.
These electrical signalling instruments are also sometimes combined
with the standard signals and points in such a manner that the standard
signals cannot be altered from "danger" to "all right," or the attitude
of the points altered without the "line clear" signal has been received
on the corresponding signalling instrument. This is accomplished by
attaching a cam to the lever or other machinery working the standard
signals or the points, the cam having a notch in it into which a pawl
falls. This pawl is moved by the handle which the attendant moves
when he works the electrical signalling instrument. Thus, when the
point or signal lever or handle has been so moved as to unlock the
electrical instrument the working of the latter by the signalman causes
the pawl to engage in the notch of the cam, and thus locks the point
or signal. The pawl is held engaged in the notch by a detent until
by the working of the electrical instrument from the station beyond
the movement of the electrical signal in obedience to its bias releases
the detent and permits the pawl to be disengaged from the cam by the
action of a counterweight or spring, when this is effected the point
ór signal is again set free.
Such interlocking of the electrical instruments and of the points and
signals may be modified so as to suit particular conditions in the
working of railways. For example, the following system of working
may be carried out by these means:-A signalman cannot telegraph
to the station before him that the line is clear until he has first put
his own standard signal to danger, or set his points right for a coming
train. Having done so, and having thus released his electrical instru-
ment he can signal electrically to the station before him that the line
is clear; but having so signalled he cannot alter his own standard signal
so as to show that the line is clear at his own station, nor can he shift
his points until he has himself received from the station beyond him
the electrical signal that the line is clear there, and has his standard
signal or point released by the action of the electrical signal.
When there are several sets of points or signals as in a station the
electrical instrument as above described may be arranged to interlock
with the several sets, so that they shall control and be controlled by
them, or that all may be controlled from a central instrument or
apparatus. For this purpose instead of employing a cam in each case a

page_text: sliding bar with notches may be arranged so as to extend along several
sets of the electrical instruments. When the pawls of all the electrical
instruments are removed from the notches in the bar the latter is free
to be moved, and when it is moved the electrical instruments cannot be
worked so as to move back their pawls, there being no notches presented
for their reception. When on the other hand the bar is moved so as to
present its notches to the pawls, any one of the electrical instruments
being worked causes its pawl to enter the notch in the bar and thus
holds it. There may be several such bars arranged to interlock with
such of the several electrical instruments as the particular conditions of
the lines may requiro.
The mechanism for effecting the interlocking of the several parts of
the apparatus resembles that which is well known and often used for
interlocking the levers of railway points and signals, for which purpose
sliding bars and pawls worked by the movement of the levers themselves
are often employed. As however according to this Invention certain of
the parts interlocked operate by electrical currents it is possible to
transmit these currents over great distances and thus to secure inter-
locking at points so far apart that mechanical connections would be
inapplicable; and in this manner by employing mechanical connections
of any known kind for the interlocking of those. levers whether for
working the points or electrical or other signals which are near each
other, and by using electrical connections such as I have described for
those which are far apart, many sets of points and signals can be brought
under one central control. Further it is obvious that in this manner not
only electrical signalling instruments such as have been described above
can be interlocked by notched sliding bars and pawls with each other,
and with the points and standard signals, but also that electrical
signalling instruments of other known constructions can be similarly
interlocked by the use of such notched sliding bars and pawls.
It will be readily understood that the before-described electrical
signalling and locking apparatus can be employed for controlling traffic
or giving signals on canals or in other localities as well as for indicating
the position of or locking turntables, swing bridges, gates, or other
objects, on the particular position of which the safety of traffic is
dependent.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Carl Heinrich Siemens in the Great Scal Patent
Office on the 3rd April 1873.
TO ALL TO WHOM THESE PRESENTS. SHALL COME, I, CARL
HEINRICH SIEMENS, of No. 3, Great George Street, Westminster, in the
County of Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Third day of October, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Carl Heinrich Siemens, Her special license
that I, the said Carl Heinrich Siemens, my executors, administrators, and
assigns, or such others as I, the said Carl Heinrich Siemens, my
executors, administrators, and assigns, should at any time agree with, and
no others, from time to time and at all times thereafter during the
term therein expressed,. should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
ELECTRICAL STEP-BY-STEP Instruments aND APPARATUS FOR GIVING AND RECEIVING
TELEGRAPHIC MESSAGES, AND FOR COMMUNICATING SIGNALS AND CONTROLLING POINT
AND SIGNAL APPARATUS ON RAILWAYS, ALSO PARTLY APPLICABLE TO OTHER
SIGNALLING PURPOSES," the result partly of a communication made to me
from abroad by Dr. Werner Siemens, of Berlin, in the Empire of
Germany, and partly of an Invention and discovery made by myself,
upon the condition (amongst others) that I, the said Carl Heinrich a
Siemens, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and seals, should particularly
describe and ascertain, the nature of the said Invention, and in what
manner the same was to be performed, and cause the same to be filed in
the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE that I, the said Carl Heinrich Siemens, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained in
and by the following statement thereof, reference being had to the
accompanying Drawings and to the figures and letters marked thereon,
that is to say :—

page_text: This Invention relates to improvements in the construction and
working of alphabetical dial telegraph instruments, whereby messages
are transmitted, received, and printed by means of electricity, and also
of electrical signalling instruments and apparatus to be used chiefly on
3 railways for the purpose of guiding and controlling the traffic and the
working of the points, signals, and other apparatus.
. The electrical step-by-step instruments ordinarily used for giving and
receiving telegraphic messages have at each end or station of the
telegraphic line two dials, one for the use of the operator in transmitting
a message, and the other on which is indicated the message received.
One part of the present Invention relates to the combination of those
two dials in one instrument, so that one dial at a station surrounded by
its finger keys serves both to indicate to the transmitter what message
he is sending, and also to indicate a message received. For this purpose
the instrument is constructed in the manner shewn in Figs. 1, 2, 3, and 4,
on Sheet I. of the accompanying Drawings. Fig. 1 represents a trans-
verse and Fig. 2. a longitudinal section; Figs. 3 and 4 represent plans of
parts in detail hereafter to be referred to. A is the case of the instru-
ment, in the upper part of which is mounted the receiving dial B with
its mechanism and index constructed and arranged in the ordinary way.
In the lower part of the case there is mounted in bearings a horizontal
shaft O provided with handles O', C", at each end, so that an operator can.
turn it with either the right or the left hand. On this shaft there is.
fixed a toothed wheel O³ gearing with a pinion D' fixed on the axis of
the rotating armature D, which by preference is of the kind known as
Siemens' cylindrical armature, and which when the shaft C revolves is
caused to rotate between the poles of a set of permanent magnets E, E,
fixed in the case, and thereby to produce the working alternating
electrical currents. On the side of the wheel it is convenient to
provide a pulley groove.O', so that the shaft O can be driven, by a band
from a treadle, wheel, or otherwise when desired. The dial of this instru-
ment being made with 26 divisions the numbers of teeth on the wheel C³
and on the pinion D' are made in the proportion of 13 to 2, so that the
armature makes 13 whole turns or 26 half turns to 2 of the shaft C,
and thus causes 13 positive and 13 negative alternating currents to be
transmitted through the conductor during every two revolutions of the
shaft C. When the dial has a greater or less number of divisions than
26 the proportions of the gearing are adjusted to suit such altered

page_text: 79
number. On the shaft C is fixed a bevil pinion C³, which gears into a
bevil wheel F' having double the number of teeth fixed on a vertical
spindle F, which spindle is therefore made to turn once round while the
shaft C turns twice, and therefore while the 13 positive and the 13
negative alternate currents are sent through the conductor. On the 5
vertical spindle F is fixed a disc wheel F³, a plan of which is shewn in
Fig. 3, having 13 pins f projecting from its face. A lever or arm G,
mounted on an axis in line with the spindle F, has mounted on it a bell-
crank lever G¹, on one arm of which is mounted a pawl g pressed at the
back by a light spring g' in a manner similar to the blade of a penknife. 1
The bell-crank lever G' is also drawn by a light spring G³ towards a
stop G', its tail G³ standing out nearly in a line with the arm G. There is
also mounted loosely on the axis of the arm G another arm H, which is
pressed against the arm G by a spring h, the pressure of which can be
adjusted by nuts h¹. The arm H is pulled by an adjustable spring h³, so ]
that the end of the arm H tends to bear against an adjustable stop h³.
The forces of the spring and of the spring hare so adjusted to each
other that when the arm G remains at rest the arm H is pulled by the
spring against the stop h³, but when the arm G is caused to move in
the direction of the arrow the friction between the faces of the arms G 2
and H caused by the pressure of the spring / bears the arm H away
from the stop h³, and causes it to bear against a surface h*, whereby
contact is made for the transmission of the currents generated by the
rotation of the armature. This occurs when the pawl g is engaged with
one of the pins f projecting from the wheel F³, so that as this wheel 2
revolves the bell crank G¹ and arm G are carried round by it. When
however the outer end or tail G'of the bell crank G' meets an obstacle K,
hereafter to be described, the bell crank is moved into the position shewn
in Fig. 3, its pawl g being then canted in opposition to the back spring g',
so that the pin f escapes the point of the pawl, whereupon the pawl by 3
the action of the spring g' is thrown back to the position indicated by
the dotted lines in Fig. 3, its point being thus clear of any of the pins f
brought round by the continued rotation of the wheel F. When the
obstacle K is removed the bell crank G³ being restored to its normal
position by the spring G³ presents its pawl within the range of the 3
pins f, one of which catching the pawl carries round the arm G until
the arm of the bell crank G again meeting an obstacle causes the pawl g
to be again released, and the movement of the arm G again to stop.
The obstacle K which throws the pawl g out of gear, as above described,

page_text: is the end of any one of the rods extending down from the finger knobs or
keys K', which are arranged round the dial B, one opposite each division
thereof. Each of these keys is pressed upwards by a spring k, and
when so pressed up the lower end of its rod is clear above the bell
crank G'. The wheel Fs as it rotates then carries round with it the
arm G, which by friction, as above described, keeps the arm H bearing
against the contact surface h', whereby a succession of alternating
currents are transmitted to the instrument B, as well as to a similar
instrument at a distant station. But when any one of the keys K³ is pressed
down by the finger the lower end of its rod comes within range of
the bell crank G', whereby the pawl g is disengaged, the arm G is
stopped, and the arm I being relieved from the frictional pressure is
drawn by the spring / away from the contact surface 7. The electrical
circuit being thus broken the currents cease to act on the instrument B,
and on the distant instrument, so that the indices of these instruments
stop at a division of their respective dials corresponding with the parti-
cular key K¹, which has been pressed down. Each of the rods K has on
it an inclined latch-shaped projection ³, which lies against a pin 、 pro-
jecting from a disc L mounted on an axis in line with the vertical
spindle F. A plan of this disc is shown in Fig. 4. A spring
this disc bearing against a fixed stop F. When any one of the finger
keys K' is pressed down, its projection being taper, in descending
pushes aside the pin 2, and thus partly turns the disc L in opposition to
the spring. When the projection has passed down below the pin l,
the spring causing the disc L to return brings the pin above the
shoulder of the projection ', whereby the rod K is held down notwith-
standing that its knob K' is relieved of the pressure of the finger. When
however another of the keys K' is pressed down the projection k³ on its
rod pushing aside one of the pins in its turn, and thereby partly
turning the disc L releases the key formerly depressed, which thereupon
is caused to rise by the action of its spring k. Thus any one of the
keys K³, when once depressed by the finger, is held down until another
is depressed, and is then released and allowed to rise. The latch-shaped
projection ¹ may be made to encircle the rod K, as shewn in Figs. 1 and.
2, so that the rod K may be turned on its own axis without interfering
with the latching action, as above described. These rods may however
be square, passing through square holes in the top plate, or may be
otherwise guided so that they cannot turn, in which case the latch /
keeps

page_text: .
may be made to project from only the one side of the rod presented
towards the pin 2 on the disc L.
A considerable part of the apparatus as above described is of well
known construction, but it has been necessary to describe it in order that
the points of novelty may be better understood. These points are 5
embodied in the following claims, which are to be understood as
embracing all that is desired to be secured in respect of this portion of
the present Invention.
First. The general arrangement substantially as herein-before described
which enables the transmitting keys and apparatus to be accommodated 10
in the same instrument with the one dial which serves to indicate to the
operator the signals he transmits to a distance, and which serves also to
indicate signals transmitted from a similar instrument at a distance.
Second. The latch arrangement of the key rods K in combination
with the spring disc L, whereby any one of the keys is held down until it 15
is released by depressing another of the keys, substantially as herein
described.
Third. The use for such apparatus of the pawl g mounted on a pivot,
and provided with a back spring, so that when it is being thrown out of
gear by the pressure of one of the pins fit is caused to turn a little in 20
opposition to the back spring, and when the pin fhas passed its point it
is caused by the back spring to return to a position clear of succeding
pins, substantially as herein-before described.
This Invention relates also to a means of actuating the printing
mechanism of such step-by-step instruments. Usually the wheel con- 25
taining the printing types is brought round like the index by a
succession of currents step-by-step, until the proper type is presented at
the printing point, and then an additional current is transmitted for the
purpose of effecting the impression. This additional current which is a
source of inconvenience and complexity is altogether dispensed with by 30
the use of mechanism which will now be described in reference to Figs. 5
and G, Sheet I. Fig. 5 represents a side view, and Fig. 6 a plan of
the mechanism for this purpose. M, M³, are the poles of the electro-
magnet which is employed to work the type wheel round in the usual
manner by causing a lever Q to oscillate between them. Between these 35
poles there are also mounted sido by side two polarized levers N, N', each
having a tail n, n', projecting from it. A stop O prevents the one

page_text: lever N from advancing to the pole M, and a similar stop O' prevents
the other lever N¹ from advancing towards the pole M, but each of the
two levers is left free, the one to approach the pole M, and the other to
approach the pole M. Between the tails of the levers n and n¹ there is
3 mounted a vertical lever P drawn by a spring P³, and having a tail P
projecting from it between an adjustable stop p and a contact surface p¹.
While the magnetic poles M. and M³ are active, causing the lever Q to
oscillate and the type wheel to revolve, the levers N and N' are both
caused to oscillate together in unison with the lever Q, but the one is
O stopped in its oscillation in the one direction, and the other is likewise
stopped in its oscillation in the other direction. The lever P-is-con-
sequently by the action of the tails n, n³, against it held in the position
shewn in Fig. 5; but when the magnet M, M', ceases to be active
(which occurs when the type wheel has been turned to the proper point
5 by the action of the alternating currents transmitted by the operator at a
distance) the levers N, N', cease to oscillate, the lever P is left free
from their action, and the spring P¹ draws it so that its tail P³ makes
contact with surface p³, and thus forms an electrical circuit whereby the
mechanism is actuated which causes the type to make its impression.
.
The levers N, N¹, as well as the lever Q, may be polarized in any
known manner. A convenient mode of effecting this is to place them
within notches in the poles or polar extensions of a magnet R, which
may be either a permanent magnet or an electro-magnet kept active by
a special local circuit. In respect of this portion of the Invention -the
5 novelty claimed is,--
Fourth. The use of apparatus substantially as herein-before described,
whereby in an electrical printing instrument the mere cessation of the
magnetic activity causes contact to be made for the purpose of actuating
the imprinting mechanism, thus dispensing with a special current for
that purpose.
The improvements on the step-by-step instruments for use on railways.
are of the following kind:-In these instruments there are employed in
dices which may be discs, semaphores, arms, or sliding frames, on which
are marked known signs, or signs having predetermined meanings.
Fig. 7, Sheet II., represents diagrammatically a side view of two such
indices constituting one form of the signalling instrument. As the two
sides are alike, it will suffice to describe the working parts of one

page_text: marked I. R' is a semaphore arm pivotted at Z', and provided with
teeth on its periphery. The movement of one of those indices from one
position to another, by causing it to present to the eye a sign different
from that which it presented before movement, gives a visible signal,
and this movement may be accompanied by the ringing of a bell or other
suitable phonic alarum, as will be hereafter described. The pallets of
an escapement a' similar to the anchor escapement employed in clocks
engage in the teeth of the semaphore arm. This escapement is attached
to and worked by the armature of an electro-magnet E', and is caused to
oscillate by a number of successive alternately positive and negative
electrical currents being made to pass through the coils of the magnet.
The arm R¹, by its own weight or the pressure of a spring, has a bias in
one direction of motion, but being held by the pallets of the escape-
ment a¹ when they are at rest, it can only move in obedience to the bias
tooth by tooth when these pallets oscillate. Thus as a number of
successive alternately positive and negative currents are required to give
a number of oscillations sufficient to change the signal an accidental
current, or a succession of currents of the same direction, or a discharge
of atmospheric clectricity makes no appreciable difference or alteration
in it. The electro-magnets and armatures may be of any of the known
kinds, and may be combined with permanent magnets. The electrical
currents may be derived from any known source of electricity, but they
should be alternately positive and negativo, as in the dial instruments
already described. The armature connected to the escapement a' is
polarized, so that the alternately positive and negative currents trans-
mitted through the coils of the magnet E' cause it to oscillate. This
oscillation besides working the escapement causes a hammer attached
to the armature to strike a bell or bells placed near it.
The arm R' may have marked on it on a red ground the words “train
on line," or other suitable term, and on a white ground the words "line
clear," or other term of equivalent meaning.
In order to provide for moving the arm R' upwards the direction of
the bias is altered by the movement of a rod, lever, or other convenient
handle which the attendant moves, and which is connected to com-
mutators, so that its movement determines the line of wires through which
the electrical currents have then to pass. The movement of this handle
while it sets the commutators also brings a weight or spring to bear
upon the arm, so as to overcome the bias which it previously had, and

page_text: give it a bias in the opposite direction. In Fig. 7, Sheet II., the
arrangement shewn for this purpose is a rod with a knob T which can
be pressed down by hand. On this rod is a sliding weight G' which, by
the depression of the rod is brought to bear on the tail of the arm R', and
so to bias it upwards. At the same time the lower end of the rod presses
down a commutating lever, so as to alter the direction of the electrical
currents, as will be hereafter described.
.
It is to be understood that at stations on either side of the station
where the instrument shewn in Fig. 7, Sheet II. is situated there are
other instruments of like character; their reciprocal operation may be
understood from the following examples:-The arm R¹ being biassed to
descend, when the attendant at the station on the up line towards the
side L' depresses his rod corresponding to T, and works his magneto-
inductor, he sends alternately positive and negative currents along the
line wire, and through the conducting parts marked 1, 2, 3, 4, to the
coils of E¹, and thence through 5, 6, 7, VIII., and IX., to earth, thus
causing the escapement a¹ to oscillate. While the armature oscillates,
the arm R¹ following the bias of its own gravity descends tooth by tooth,
and brings before an aperture in the cover of the instruments the words
"line clear," while the words "train on line" become hidden behind the
cover. A similar action would take place for the "down line" indicator
marked II. if the currents were transmitted, from a station towards I.
If, however (as shewn in Fig. 7, Sheet II.,) the arm R' is down, and the
operator depresses his own handle To, then the weight G resting on the
tail of R³ gives it a. bias in the direction opposite to its own gravity, and
therefore a tendency to ascend. Simultaneously with the depression of
the handle T contact is interrupted between I., II., VI., VII., VIII.,
and IX., but established between VI. and X., as also II. and XI., and
when now by turning the handle K of the magneto-inductor alternating
currents are produced, they will pass from earth inductor S, XI., II.,
III., IV., through the electro-magnet E³, V., VI., X., over 1, through
line L' to the next station, which will receive the signal "line clear" in
the manner before described on the down line indicator, while the
arm R³ will ascend in consequence of the bias given to it by the weight.
G' and the motion of its own escapement a³, and will block the down
line by showing the words "train on line." The action therefore of
depressing the handle T takes the signal off the preceding station, and
at the same time shews the the block signal on the operator's own instru-

page_text: ment, which block signal can only be removed by a similar operation at
the succeeding stations.
As the commutators have to be arranged for the passage of either
currents sent out or currents received it is sometimes convenient for the
sake of simplicity to construct and arrange the electro-magnets which
work the indices, so that one half of each, as for example, one of the two
bobbins of each magnet, shall be used exclusively for the currents sent
out, and the others for those received, or one-half of the coil on each side
of the two bobbins of a magnet may be employed for the passage of the.
currents sent, and the other half for those received, or the electro-magnet
of each instrument may be in duplicate, the one being employed when
currents are sent, and the other when they are received; or one electro-
magnet with its commutator in its normal position may be employed for
currents received, and for currents sent when its commutator is depressed.
Fig. 8, Sheet II., shows an arrangement of commutators in con-
nection with an instrument such as has been described, so that the
inner coils of the electro-magnets receive the alternating currents
arriving from either line, and 'the currents sent from the instrument
pass through their outer coils. It will suffice to explain one operation
with this instrument. Supposing the attendant at the instrument
shewn in Fig. 8, Sheet II., intends blocking the down line, he depresses
the handle T, and turns the handle K. A. succession of alternating
currents will then pass from earth to + through inductor ± through
the outside coil of the "down" magnet E, through L, 3, and P¹ into
line I, and arrive at the "down line" indicator of the preceding
station by a line corresponding to I, through P³, », I, W³, signal
bell up W', through the inner coil of the down line indicator to earth.
It may be readily understood that instead of guiding the currents as
described through one coil at a time, the coils might be wound with
double wires, the convolutions of the one being employed for arriving
currents, and those of the other for departing currents, the arrangement
remaining in other respect as described. And in like manner the
electro-magnets might be in duplicate, one being employed for arriving
and the other for departing currents.
It is to be understood that in applying instruments such as are
described above to block signalling on railways, there are combined
at each block station two indicators, one for up and one for down trains

page_text: with one inductor, as shewn in perspective in Fig. 9, Sheet II., together
with additional mechanism which will be hereafter explained. A
greater number of indices may however be combined with one inductor
at stations where there are branch lines, semaphores, or points. The
successive stations or signal boxes are connected by one wire which
is sufficient for transmitting the required electrical currents in both
directions. The attendant at a station, in giving a signal from his
station to another, moves a handle or depresses a plunger such as
T1, or T2, which at the same time gives his own signal a bias in one
direction and sets the commutators right for the transmission of the
electrical currents, and he works the magneto-electric machine which
produces those currents by turning the handle K.
.
The signals and commutators may be arranged in various ways so.
as to render them suited to various systems of signalling. In order
that their operation may be understood, one such arrangement has
been described in detail above, the commutators being so arranged
that each instrument sends currents by the line opposite to that by
which it receives currents, that is to say, when the handle T is
depressed, the current is sent by the line L, and when T¹ is depressed,
it is sent by I, and the handle or plunger which sets the commutator
being made to bias the index at its own station so as to give the block
signal, the operation is as follows:-The attendant moves the handle
T, and thus gives bias to his own down line signal, so that it will be
moved to "block," and sets the commutators so that a current from
his magneto-electric machine shall be transmitted to the next station
on the line L'. While he keeps the handle in the position to which he
has moved it, he works the magneto-machine and thus removes the
"block" signal from the station next before him on the line L', and
moves his own signal to "block." The attendant at the next station beyond
on the line L³ performs similar operations in his turn, and thus a train
in either direction is always signalled to stop at a station unless the
attendant at the next station beyond (that is to say the station to
which the train is proceeding) has removed the block signal at the
station which the train has reached. It will be seen that before any
signal can be given by one of these instruments it is necessary that the
operator should perform simultaneously two operations, viz., he must
move the handle and at the same time work the instrument for pro-
ducing the electrical currents.

page_text: In some cases it may be desired to transmit a signal without actuating
the signal indices above described. To effect this the instrument for
producing the electrical currents is provided with a contact maker so
_arranged that it will pass oither only positive or only negative currents,
and a separate key, commutator, or plunger is placed between the line
wire and the signalling instrument above described, whereby the latter
may be cut out of circuit and the aforesaid single current contact
maker be put in communication with the line wire on either side. An
electro-magnet is also provided through which these currents are
passed and the armature of which is thereby made to actuate a bell or
visible signal distinct from the signalling instrument above described.
This electro-magnet is in the same circuit as the coils of the said
signalling instruments, but the indices of the latter are not actuated by
the aforesaid single currents as these are not alternately positive and
negative.
The arrangement is shown in Fig. 8, Sheet II. P. and P are the
plungers, keys, or contact makers, the depression of which cuts either the
up or the down index out of circuit and brings the line wire of either.
side into direct communication with the magneto-indicator. The latter
is so constructed that of the two currents which are produced at one
revolution of the bobbin only one is permitted to enter the line, the
current being interrupted at the time the second current would pass.
To obtain this result the spindle of the revolving bobbin is for a short
distance cut in half and the half taken away, replaced by a piece of
insulating material or insulated piece of metal. One contact spring II
is in communication with either line wire via p or p³, and receives the
current produced during one half the revolution of the bobbin (which is
in connection by + to earth), when the spring II bears against the
metallic part of the spindle. It is to be understood that the contact is
broken, and therefore the opposite current is prevented from entering
the line when the spring II is on the insulated part of the bobbin spindle.
The contact spring + is however in constant metallic contact with either
line via the handles T or To when depressed. The latter spring + therefore
communicates both currents to either line. The currents all of like
kind passing by the spring II intend to sound a bell or gong in order to
forewarn the signalman of a station towards which a train is proceeding
of the departure of a train, will pass from the instrument Fig. 8,
Sheet II. for an up train by depressing the plunger P' along the line L',

page_text: and arrive at the next station along the line corresponding to L³, the
route being from earth through + II p', P', ', I, and at the next
station through L, P, , L', W, through coils of up bell W* through
one or both coils of down magnet to earth. The index will not be
affected, but the gong or bell will give any number of vibrating strokes
corresponding to the manipulation of the magneto-inductor.
A modified apparatus for warning signalmen of the arrival of trains
by means of audible signals sounded on bells or gongs is shown in
general side view at Fig. 12, and in plan, Fig. 12*, Sheet III., and in
detail in side view at Fig. 10, Sheet II., and end view, Fig. 11, Sheet II.
a is a segment similar to the semaphore arm described above, which
turns upon an axis B, and is held upwards by a spring O. E, E, is an
electro-magnet, between the poles of which one pole end of a permanent
magnet H oscillates upon centres G, G. The magnet H has fixed on it
a piece K to which are fixed two spring pawls L, L, which engage with
the teeth of the segment a. The latter ascending half a tooth at each
single stroke of K, after passing the last tooth is made to complete its
motion by the spring O. The axis B, half of which is cut away, is thus
turned, so that a projection D from a wheel M is enabled to clear it.
The wheel M influenced by a weight Q (Sheet II.), can then move in
the direction of the arrow until a pin N which rotates with the wheel M
reaches the arm O, P, of the segment, and forces the same down the
spring pawls L, L, allowing the teeth of the segment to pass them. The
wheel continues its motion till it is stopped by the projection D resting
again upon the part of the axis B which is not cut away. The arrange-
ment whereby the bell is struck is shown in Fig. 12, Sheet III. The
weight Q is suspended inside a pillar and gives rotating motion to the
wheel M; the latter carries on its face a number of teeth R, R, R, which
passing successively projections U, Ụ, fixed to the spindle S, S, cause
the same to vibrate to and fro. A hammer T attached by an arm to the
spindle S is thus caused to strike against the bell through suitable
openings in the roof which covers the apparatus.
Bell apparatus, such as have just been described, may be in circuit
with block signals, and worked by single currents by overbalancing the
polarity of one pole of the relay, so as to act in place of a spring in the
manner of what is known as Siemens' polarized relay, or they may be
connected to separate lines as may be required. There may be also
affixed to the spindle of the wheel M, upon part of which is coiled the

page_text: cord by which the weight Q is suspended, a certain number of discs
having incisions upon their circumference for the purpose of producing
certain predetermined signals such as those of the Morse code. By the
insertion of certain keys the signalman is enabled to send such signals,
whereby he may call for assistance or notify danger or obstruction to i
the termini or other stations. The act of inserting the key starts the
mechanism mechanically, and the condition of the key determines the
choice of the kind of message or call for help. The motion of the
mechanism causes the necessary contacts or interruptions to be made
with a battery, and prints the signals on an inker or other Morse 1
instrument at the station, the line wire of which is connected to the bell.
The message is therefore dispatched mechanically or automatically by
the mere insertion of a key lever or pin, the condition of which
determines the choice of a prearranged code. The mechanism for this
purpose is shown in Fig. 13, Sheet III., in side view, and in end view in 1
Fig. 14, Sheet III. a, b, c, d, e, f, are discs having incisions, shewn
partly in section, Fig. 14. The arm 1 of a compound lever 1, 2, is kept
by a spring in contact with any one of these discs, and their undulations as
they revolve cause contact to be made and broken at 10, one polo of a
battery being connected to the lever and the other to the contact
piece 10, a Morse instrument intervening in the circuit. The undulations
may be so arranged as to interrupt a persistent current, or to establish
temporary contact. A key g is inserted (as shewn in Fig. 13) having a
length of pin which determines the choice of the disc against which the
arm 1 will bear. Instead of a separate key for cach disc, a single key
with its pin made to shift to different lengths might be used. As shewn
in the Drawing the arm 2 resting on the pin of a key of the length
suited to e causes the arm 1 to rest against the disc marked e. The
release of the train of wheels which moves the disc spindle is caused by
the insertion of the key passing and pushing against the pin 7, the
elongation of which presses against the lower spring pawl (see Fig. 10),
and at the same time moves the armature so as to clear the top
pawl. The segment is thus allowed to rise and to start the train of

page_text: electrical communication unless when the standard signal is set at
"-danger," or the points are in a particular attitude. By these means
the electrical signal clearing the line at a preceding station cannot be
given until the standard signal at the sending station has first been put
to "danger," or the points there set in their proper attitude. These
connections are of the following kind:-The lever winch or handle which
works a standard signal or a set of points is made also to work a com-
mutator, which in one position of the signal or points allows the passage
of an electrical current to or from the electrical signalling apparatus at
the station, and in another position of the signal or point cuts the
electrical circuit off from the signalling instrument. Fig. 15, Sheet IV.,
shews diagrammatically an arrangement for this purpose.
"
The arms U, U₁, of the semaphore or standard signal are moved
by tightening or slackening the cords V, W, by means of turning the
discs O and D round their common centre Y. It may be here
remarked that the Figure shews semaphore signals made according
to the system sometimes adopted on the Continent, viz., the arm in a
horizontal position signifying "blocked" or "stop," the arm pointing
upwards signifying "line clear" or "go on.' It is obvious that the
positions of the semaphore arms, such as are adopted in England, could
be governed by similar mechanism. When the cord is slackened,
as W, the semaphore U descends to the horizontal position by its own
gravity, indicating "stop," and it is held in that position by a projection
E from the diso D striking against a stop F. A cam on the disc C
in that attitude rests upon a roller at the end of a contact lever, and
brings the parts 1 and 2 into electrical circuit, while 3 is cut off
from the circuit. In that position only, that is, when the semaphore
shews "danger, can the signals in connection with the up line be
received or given. With the position of the semaphore U' contact
is established between 1 and 3, but is cut off from the circuit. The
signalman therefore is forced, after the passing of a train, to first
put his own signal on to "stop" before he can take it off the station
whence the train came.
"
The clectrical signalling instruments are also sometimes combined
with the standard signals and points in such a manner that the
standard signals cannot be altered from " danger" to "all right",
or the attitude of the points altered unless the "line clear"
been received on the corresponding signalling instrument. This is
signal
has

page_text: accomplished by providing a cam or notch in connection with the
lever, disc, sliding rod or bar, or other machinery working the standard
signals or points; a pawl engages with the cam or notch.
This pawl
is moved by the handle which the attendant moves when he works
the electrical signalling instrument. Thus when the point or signal
lever or handle has been so moved as to unlock the electrical
instrument, the working of the latter by the signalman causes tho
pawl to engage in the notch of the cam and thus locks the point
or signal. The pawl is held engaged in the notch by a detent, until
by the working of the electrical instrument from the station beyond,
the movement of the electrical signal in obedience to its bias releases
the detent and permits the pawl to be disengaged from the cam or
notch by the action of a counterweight or spring; when this is
effected the point or signal is again set free.
The arrangement is shown diagrammatically in Fig. 16, Sheet IV.
By turning the handle K. the position of the semaphore arms is
determined by means of cords. If such arm is permitted to descend
by its own gravity it will place itself, determined by the length of
the pulling cords or wires, in the horizontal position of "stop," and
press the handle K against the stop F. In this position (shewn in
the Figure in respect of the up line) a notch in a disc D which turns
with the handle K is brought to face a spring pawl which, if depressed,
prevents the turning of the handle K, and therewith the moving of
the semaphore arm. Thus the depression of the commutator or
plunger T for giving electrical block signals is possible only when ?
the semaphore stands horizontally, showing "stop," when the position
of the winch handle K permits the depression of the plunger T, the
spring pawl is depressed and held down into the notch of the disc B
by means of the rod G, G. The shoulder II fixed to the rod G, G,
descends and permits the lever L, M, N, which turns round the centre 3
M, subject to the tension of the spring P, to take the position shewn
in respect of the up line commutator to the left. If now alternating
currents ho sent by turning the indicator, the segment carrying the
words "go on " and "stop" will ascend and show behind the "aperture"
of the cover the word "stop," while at the same time the currents 3
pass through line L³ to the preceding station and take the signal off,
that is, show the words "
go on "
When the segment
R' bas ascended its axis Z, half of which is cut off, having turned,
or line clear.

page_text: prevents the lever L, M, N, from returning. In consequence whereof,
the shoulder H with the rod G, G, cannot rise, and therefore the signal-
man cannot alter his signal as long as the electrical index shews the
"block" signal, nor can he move his semaphore arm. If however
the signalman at the next or succeeding station takes his signal off,
then the segment R. descending brings the axis Z into such a position
that the lever L, M, N, gets clear of the shoulder H, permitting the
rod G, G, to ascend. In consequence thereof the pawl is withdrawn
by its spring from the notch of the disc D, and consequently the winch
handle K, and with it the semaphore arm, are left free to be moved.
In this manner the signals are made to depend upon each other.
Such interlocking of electrical instruments and of the points and
signals may be modified so as to suit particular conditions in the
working of railways. For example, the following system of working may
be carried on by these means:-A signalman cannot telegraph to the
station before (or preceding him) that the line is clear until he has first
put his own standard signal to danger or set his points right for a
coming train. Having done so and having thus released his electrical
instrument he can signal electrically to the station before him that the
line is clear, but having so signalled he cannot alter his own standard
signal so as to show that the line is clear at his own station, nor can he
shift his points until he has himself received from the station beyond
him the electrical signal that the line is clear there, and has his standard
signal or point released by the action of the electrical signal.
When there are several sets of points or signals, as in a station, the
electrical instruments, as above described, may be arranged to interlock
with the several sets, so that they shall control and be controlled by
them, or that all shall be controlled from a central instrument or appa-
ratus. For this purpose instead of employing a cam or notch in each
case they may be geared or connected so as to act together or one at a
time, or a sliding bar with notches may be arranged so as to extend
along several sets of the electrical instruments. When the pawls of all
the electrical instruments are removed from the notches in the bar the
latter is free to be moved, and when it is moved the electrical instru-
ments cannot be worked so as to move back their pawls, there being "no
notches presented for their reception; when on the other hand the bar is
moved so as to present its notches to the pawls, any one of the electrical
instruments being worked causes its pawl to enter the notch in the bar

page_text: and thus holds it. There may be several such bars arranged to interlock
with such of the several electrical instruments as the special conditions
may require.
The mechanism for effecting this interlocking of the several parts of
the apparatus resembles that which is well known and often used for
interlocking the lovers of railway points and signals, for which purpose
sliding bars and pawls worked by the movement of the levers themselves
are often employed. As however according to this Invention certain
parts interlocked operate by electrical currents, it is possible to transmit
these currents over great distances and thus to secure interlocking at
points so far apart that mechanical connections would be inapplicable;
and in this manner by employing mechanical connections of any known
kind for the interlocking of those levers, whether for working the points
or electrical or other signals which are near each other, and by using
electrical connections such as I have described for those which are far
apart, many sets of points and signals may be brought under one central
control.
66
One such arrangement is shewn diagrammatically in Fig. 17,
Sheet V., a front view of the apparatus being shewn in Fig. 18,
and an end view in Fig. 19, Sheet II. It is to be understood that:
in this case the marks on the semaphore arms are inverted from the
position described with reference to the instruments working the block
system. B' is a sliding bar carrying a lever C¹. There are as many
bars as there are levers L, these bars being arranged side by side and
each provided with a lever, such as C¹ for each lever L, and a notch
for each pawl p. In this instance the station is represented as
"blocked" for an incoming train; the outside signal IV. shews
stop;" the pawl p is in the notch of disc D and held down by
the rod G which is held down by its shoulder H bearing against the
lever L, M, N, as before described; the corresponding indicator IV.
of the station apparatus is locked, so that the signalman can neither
move his handle K nor the plunger T, the 3 points I., II., III., being
free as long as the electrical index of each is in the position shewn;
when each of the 3 points is locked in its normal position tho signal-
man is enabled to take the signal off the outsido semaphore, he must
therefore put the indices I., II., III., into the position of index IV".,
that is to say, the levers L, M, N, rods G, levers L, and pawls p must
stand in the position indicated at index IV. before the latter can be

page_text: altered; only then the sliding bar B¹ may be moved and allow the
lever L' to take up the position shewn at L, I³, and L*; the handle K
may then be turned, and thereby the signal taken off the outside sema-
phore. Therefore a train can never enter the station from that direction
unless all the points are locked in their normal position.
A modified arrangement for protecting a railway station is shown
diagrammatically in Fig. 20, Sheet IV. B is the indicating instrument
as before described, with this difference, that the arm "R" when
shewing "line clear" interrupts a line in connection with the points.
The official at the station therefore is prevented from giving any signals
to the points W, W, as long as the distant signal stands at "line clear."
Only when the train has entered and the distance signal has blocked
the station, the indicator at the station showing "red" the connection
is re-established by the descending of the arm. To the arms connected
to the points also in connection with a second line are provided spring
contacts which allow the passage of a current only when they are up, ·
that is to say, when they are locked in their normal position. It will
be understood that any number of points may be brought within the
control of the circuit. If therefore the distance semaphore S is blocked
points may be worked freely for shunting trains within the station, and
the signal at S cannot be taken off by the signalman at the station
unless all the points stand locked in their normal position. The inductor
of the electrical instrument at the points may be dispensed with in this
arrangement, and the locking performed mechanically.
There may also be several sets of contact springs upon each arm
of a point, in order to ensure that an optical "unblocking" of a branch
line or lines cannot take place unless such set of points referring to
such branch lines stand locked in their normal position. The line
therefore by which the official at the station takes the signal
"off,"
the semaphore which protects the station is passed through all those
points which must be in a certain position for the entry of a train,
and the continuity of such line is interrupted as long as the points
do not stand locked in the position required for the safe entry of the
train. Therefore the official at the station cannot open the road into the
station unless all points stand locked in the correct position.
The opening of the points after the entry of a train is performed by
the attendant at the station by a second line from which the currents
pass through all the coils of the electro-magnets of the several points,

page_text: and move their cscapements in such a manner as to unlock the points.
This second line however is interrupted by the indicator at the station
so long as it shows "line clear," and also as long as the distance signal
is "off," or the official is prevented mechanically from sending any
current into the line during that time, so that he cannot clear or free the
points before the protecting standard signal is at danger.
At an intermediate station or central station which trains may enter
in several directions at the same time to several platforms, several sets
of these apparatus are provided, one for each line, with its points, as
has just been described; but such points as refer to the same lines are
interlocked in such a manner that when the signal has been taken off
one the other must be locked into its normal position. The manner
in which this is donc is similar to that which has been previously
explained. Further, it is obvious that in this manner not only electrical
signalling instruments such as have been described can be interlocked
. by notched sliding bars and pawls with each other, and with the points
and standard signals, but also that electrical signals of any other known
construction can be similarly interlocked by the use of such notched
sliding bars and pawls.
It will be readily understood that the before-described electrical
signalling and locking apparatus can be employed for controlling
traffic, or giving signals on canals or in other localitics, as well as
for indicating the position, or for locking turntables, swing bridges,
gates, or other objects on the particular position of which the safety of
traffic is dependent.
The nature of the said Invention having thus been described, and the
manner in which the same is to be performed, it is to be understood that
no claim is made to such parts of the several apparatus described as arc
old and well known, these having been described in order that the
several parts of the present Invention may be better understood; but
the novel features now claimed in respect to those portions of the In-
vention which have been last set forth are as follows:-
Fifth. The arrangement of electrical signalling apparatus, sub-
stantially as herein described, in such a manner that their signals
can only be given or altered by the operation of a number of successive, 3
alternating, positive, and negative currents, whereby they are guarded
from the influence of accidental or defective currents, and atmospheric
clectricity.

page_text: Sixth. The use for electrical signalling apparatus such as has been
above referred to of a semaphore arm or other index biassed by the
shifting of a weight or spring, so as to move in one direction or the .
other when permitted to do so by the action of an escapement worked
by alternating currents, substantially as herein described.
Seventh. The combination of electrical signalling apparatus such as
has been referred to above with the standard signals of railways, canals,
or other lines of communication, in such a manner that a signalman
cannot work his electrical instrument to signal "line clear" to another
station until he has placed his standard signal to "danger," substantially
as herein described.
"
Eighth. The combination of electrical and standard signalling appa-
ratus such as have been above referred to, in such a manner that a
signalman cannot move his standard signal to indicate "line clear
until he has received the electrical line clear signal from another station,
substantially as herein described.
Ninth. The interlocking, substantially as herein described, of the
points and signals with electrical signalling apparatus at a railway station
or junction.
Tenth. The arrangement of commutator in combination with a
magneto-inductor and electrical signalling apparatus, whereby while
the inductor sends alternating positive and negative currents to produce
certain effects on the signalling instruments, as for example, the moving
of an index step by step only such of the currents as are either positive
or negative are utilised for producing other effects, as for example, the
sounding of an alarum, substantially as herein described.
In witness whereof, I, the said Carl Heinrich Siemens, have here-
unto set my hand and seal, this Third day of April, in the year of
our Lord One thousand eight hundred and seventy-three.