Improvements in and connected with Apparatus for Controlling the Motion of Elevators or Lifts.
Year: 1898

page_text: Date of Application, 24th Jan., 1898-Accepted, 7th May, 1898
Improvements in and connected with Apparatus for Controlling the
Motion of Elevators or Lifts.
A communication from abroad by OTIS BROTHERS & COMPANY (Incorporated),
of Yonkers, in the State of New York, United States of America.
We, OTIS ELEVATOR COMPANY LIMITED, of 4, Queen Victoria Street, in the
City of London, Manufacturers, do hereby declare the nature of this invention
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to certain improvements in and connected with apparatus
for controlling the motion of elevators or lifts.
a
The first part of the invention relates to the electrical operation of elevators
by the use of a single push-button system, and it has for its object to provide
simple, cheap and effective system of controlling elevators, and it consists in the
various features of construction and arrangement of parts having the general
mode of operation substantially as herein after more particularly set forth.
In the accompanying drawings:
Fig. 1 is a diagrammatic representation of devices arranged to operate in accord-
ance with this part of the invention;
Fig. 2 is a similar diagrammatic representation, showing another embodiment
of the invention;
Figs. 3 and 4 are, respectively, side and sectional views of a floor controller
such as it is preferred to use in connection with the system;
Figs. 5 and 6 are, respectively, side and end views of an electric reversing
switch such as it is preferred to use;
Fig. 7 is a side view of a modified form of drum for the floor controller; and
Fig. 8 is a diagram of a modification.
Heretofore means have been provided for electrically operating elevators by
means of push-buttons (and by push-buttons is meant any sort of electrical switch
or device for controlling the circuits) arranged on the different floors so that the
elevator can be set in motion through the engine and brought to any desired
floor, and as ordinarily constructed these mechanisms are relatively complex and
expensive, and it is the object of this part of the present invention to provide
means whereby by the use of a single push-button or circuit-closer in connection
with each floor the elevator car may be brought automatically to that floor ready
for use.
As a further improvement, by this arrangement it is not necessary that the
operator should see the car and break the circuit to stop it, as it will automatically
stop at the floor to which it is called. Further, it is not necessary to keep the
button closed, as an ordinary pressure of a few seconds' duration is all that is
required to call the elevator to the desired floor, regardless of its position.
Again, the system is non-interfering in that when a push-button at one floor
has been pressed the pressure of any push-buttons at other floors will not interfere

page_text: thereof, securing a spring-pressed yielding contact between them. B represents
a mechanically pressed pin on the magnet tending to separate the contacts and
overcome any electric adhesion or other tendency to stick.
While, as above intimated, the electric reversing switch just described is the
preferred form, and while it is described sufficiently to enable its operation to be
understood in the present case, it is not herein claimed but may form the subject
matter of a separate application.
In order to operate the electric reversing switch automatically when any push-
button corresponding to any floor or stopping place is operated there is provided
what is termed a floor controller C, and this is indicated diagrammatically in the
drawings, and the preferred mechanical embodiment of which is shown more
particularly in Figs. 3 and 4. This controller is connected in some suitable way
to be operated in unison with the motor or the engine of the car, and there is
indicated at Fig. 3 a sprocket wheel A mounted or connected to the shaft A of
the motor, and a sprocket chain connecting said sprocket wheel A with the
sprocket wheel C¹ on the controller. The controller as shown embodies a cylinder
or drum C² on the face of which are arranged two spiral contacts C3 C4, or what
is in effect a single spiral with an electrical brake between the two portions thereof.
This drum may be rotated continuously in a single plane, but in order to give
sufficient length to the contacts C3 C4 they are preferably arranged spirally on
a smaller drum as indicated, and the drum is caused to move longitudinally as
well as rotatively, and in the present instance there is shown a worm shaft (5
fixed in the frame, and connected therewith is a disc C to which the arms carrying
the brushes bearing on the spiral contacts are supported, only one being shown
in Figure 4 for convenience of illustration. The drum C is screw threaded to
fit the worm shaft C5 and is rotated thereon by any suitable means, as for instance
the cross-head C7 connected to move with the sprocket wheel C¹, and it will be
apparent that while the drum C³ rotates in one direction or the other it is also
moved longitudinally on the worm shaft C5 and as the pitch of the spiral con-
tacts C3 C4 on the drum corresponds to the pitch of the worm wheel the brushes
will continuously bear on said spiral contacts and travel over the same as the
drum is rotated.
While this is the preferred construction of the floor controller, it is apparent
that the principles thereof can be embodied in other forms, and instead of being
a rotating drum it may be a moving plate or other similar device, the essential
feature being that it shall automatically control the circuits, substantially in the
manner hereinafter set forth.
In the present arrangement in connection with the floor controller there are
eight brushes bearing on the spiral contacts which are sufficient to control an
elevator used for six floors or stopping places or stations and in the diagram
instead of showing the spiral contacts there are shown contacts in the form of
two semicircles, which is the equivalent and may be used, except that it requires
too large a drum for convenience of operation, the principles of operation, however,
being precisely the same as when the spiral contacts are used. There is a brush c
normally engaging contact C3 and connected by a conductor with one of the
coils B of one of the magnets B1 B2 of the electric reversing switch B and there
is another brush c¹ normally bearing on the contact C connected to the coil B10
of the other magnet B1 B2 of the reversing switch, and it will be observed that
both of these magnets are connected directly to the minus feeding main, and
when a current flows through one or the other of the coils B9 B10 the corresponding
magnet B1 B2 is energized and the armature B³ moved to one or the other side
to close the circuit between the double faced contacts and one or the other of the
set of contacts corresponding with the magnet energized and consequently the
circuits through the motor will be in a direction to cause it to raise or lower
the elevator as required.
Also arranged in connection with the floor controller are a series of brushes f¹ f
f f f f, one for each floor or stopping place of the elevator car and numbered

page_text: the elevator motor and breaking the circuit and stopping the car. If in the
meantime any other push button as g2 g is operated, the circuit cannot be com-
pleted so as to interfere with the travel of the car until it reaches its destination,
when the circuit will be broken at the floor controller and the car remain at the
desired station.
When the car arrives at the desired floor if the door of the well is opened,
breaking the contact, it will be obvious that the car cannot be started until
such contact is closed. It is also obvious that in order to prevent any one at an
intermediate floor operating the door, well known contrivances may be used which
will prevent the opening of the door except when the elevator car is opposite
thereto. If then the elevator being at the top floor it is desired at any other floor
the corresponding push button is pressed and the well doors being closed as before
the circuit will be completed except that the reversing switch will be operated
to close the circuits through the motor to cause it to move the elevator in a down-
ward direction, and when it has once started the push button may be released
and no one can interfere with the operation of the elevator until it reaches its
destination.
In Fig. 2 there is shown a substantially similar invention embodied in a some-
what different arrangement and better adapted for use in connection with passenger
elevators, and in this case corresponding parts are correspondingly lettered and
need not be specifically described. The motor in this case is shown as a shunt
field motor in which the coil A is in the shunt field and there is a coil A5 in the
armature circuit which may be in the form of a series field coil or an external
resistance, and there is shown a switch S, controlling the circuits, which is
adapted to be operated by the automatic stop motion device in common use with
elevators or by other well known appliances and which have no immediate con-
nection with the present invention. In this diagram is shown a set of push buttons
arranged in the car, indicated at I, and it will be seen that the circuit H is
extended into the car to include a gate or door contact 7, and it also includes a
push button g7, by means of which the circuit can be broken at any time by a
person on the car, so that in case of emergency or change of purpose the car can
be immediately stopped at any desired position. The push buttons in the car
are lettered correspondingly to the push buttons at the floor landings, and the
connections need not be further described than to say that closure of a push
button corresponding to any floor at the floor landing or on the car will close the
circuit through the reversing switch, which will close the circuit through the
motor in the proper direction and move the car and the floor controller, and as
before stated this being closed the push-button can be released, and the closure
of any other push button corresponding to any floor will not interfere with the
operation of the elevator, but the breaking of the circuit by push button g7, will
stop the car at once. It will also be noticed that the car cannot be started until
the gate or door thereon is closed as well as the doors of the well.
In the operation of fast speed elevators or in cases where the load varies, or in
any other case where on account of the varying momentum of the masses in motion
it is difficult to stop the car automatically at the exact position desired, under
the varying loads or speeds, it has been found desirable to provide some means
to reduce the speed of the car before it reaches the floor at which the automatic
stop is to be made, and in this way the speed is reduced to such an extent from
its normal speed that the car can finally be brought to rest at practically the
exact position under all conditions of load or speed.
This slow speed before the stop is arranged to be produced automatically, and
may be accomplished in various ways, as by a circuit controlling an additional
shunt field winding, a short-circuiting resistance in the shunt field making a
parallel circuit to the armature, or other equivalent means, and in the present
instance there is shown an additional shunt field winding automatically controlled
by the floor controller. This is illustrated in Figs. 2 and 7, and while various
ways of accomplishing this may be used, the one adopted is simple and effective.

page_text: source of power M, may be a galvanic battery, storage battery or any other well
known source of supply and is useful more especially when high voltage currents
are used to operate the motor.
While there is shown the floor controller operated by connections with the shaft
of the motor, as above explained, it may be operated from any other part of the
apparatus, and in some cases, as for instance, where the cable operating the car
is liable to slip on the sheaves or become stretched or otherwise out of adjustment
so that the car might not be stopped exactly at the desired position when the
controller is operated by the motor, the floor controller is arranged to be operated
by some mechanical connection from the car, and in this way there is less liability
of variations in action between the controller and car. In Fig. 8 there is illus-
trated diagrammatically one way of accomplishing this object, in which A
represents the motor shaft as before and A6 a drum thereon, operating the cables N
and N', connected with the car X, and counterweight X respectively, passing
over the sheaves as indicated. In this particular arrangement the car and
counter-weight are shown connected by a sprocket-chain N2, passing over a sprocket
wheel N³, on a shaft N, carrying a pinion N³, or other means connected to the
wheel C, of the floor controller. This is a typical connection, and it will be seen
that in this way the movements of the floor controller are more directly connected
with the movements of the elevator car, so that there is less liability of inaccurate
movements or failure to stop at the desired point when the circuit is broken
automatically by the floor controller. In this way there are positive and direct
connections between the floor controller and the car.
The second part of the invention relates to the electrical operation of elevators
by a two button system, and it has for its object to provide a simple, cheap and
effective apparatus adapted for use with dumb waiters, small elevators and the
like, wherein the current used to operate the motor is also used in controlling
the operations of the motor in raising and lowering the car. This part of the
invention is illustrated in Figs. 9 and 10.
Fig. 9 being a general elevation of an elevator and operating devices; and
Fig. 10 a diagram of the circuits.
In these figures some of the same letters of reference are used as in Figs. 1 to 8
but they do not necessarily refer to corresponding parts.
One of the special objects of this arrangement is to provide for the electrical
operation of elevators in the simplest and most inexpensive manner and to also
provide that the apparatus shall be controlled simply by the pressure of a push-
button or the manipulation of a similar switch, and that the electric circuit shall
be opened and closed and directed in the proper course to operate the elevator
without the interposition of regulating devices or similar mechanism, and the
arrangement is especially applicable to dumb waiters or carriers requiring rela-
tively small power, although it can be applied to larger elevators capable of carrying
passengers as well as freight.
In the drawings is represented a conventional form of elevator operated by an
electric motor, in which A is a winding drum over and around which pass the
cables A1, A2, the former of which is connected with the car C, and the latter of
which is connected to a counterweight C¹. The drum A, is represented as being
driven from a shaft B₁, of an electric motor B, the shaft being directly connected
to the armature and arranged in connection with the shaft is a brake device D,
controlled by an electro-magnet D', the brake being of the kind that is normally
on except when the magnet is energized, when it is released so as to allow the
shaft to rotate freely, but will be automatically applied as soon as the circuit of
the magnet is broken or the current falls below the normal limits.
Connected with the motor there must be some sort of means for controlling
the circuits thereof, so as to operate it in the desired direction, and there is shown
an electric reversing switch E similar to that shewn in Fig. 5, in the present
instance mounted directly on the motor, although it can be arranged in any
desired position. This electric reversing switch is arranged so that in its normal

page_text: Also arranged in this circuit is a resistance device H, shown in the present
instance in the form of lamps, and the terminal e, of this circuit while shown
detached is supposed to be joined to the minus terminal of the leading-in
conductor.
The conductor e, is shown as leading to a switch I, on the car, and including
contacts elo, controlled by the door of the car. The switch I, is placed in the car
so that the operator therein can conveniently break the circuit by operating the
switch I, although, of course, the movement of the door of the car can perform
the same function, and in fact if the push-buttons operate correctly the circuit
will be broken on releasing either of the push-buttons which has been operated
to move the car so that while the switch I, is not a necessity it is sometimes
desirable to place it in the car as an emergency switch, and more especially to
prevent anyone from starting the car by pressing any one of the push-buttons
at one of the landings while the car is occupied.
There are shown the automatic stop motion switches F, F, as arranged in the
circuits e³, e, and they are adapted to be operated by the car or counterweight,
as before explained, and it will be understood that they break the circuit from
any one of the push-buttons of the up or down series if the car moves beyond the
predetermined limit and the circuit is not broken at the proper time by the
operator.
The operation of the device will be understood from the diagram, and if for
instance, any one of the push-buttons g, is pressed closing the connection between
the conductors e7 and et, the circuit may be traced from the plus terminal, through
the conductor e², the magnet coil e¹, the automatic stop switch F,
conductor e, push-button g, conductor c³, to the terminal e³, of the
minus leading-in wire and including the resistance H, it being understood
that the doors of all the floors in the well are closed. This will energize the coil e¹
for instance, and attract the armature E³, so that the contacts a-a³, engage
contacts b, respectively, and the current of the motor may be traced from the
plus terminal through the contact b, contact a, brake magnet D', to contacts a³, b³,
and the minus terminal. The contact a, being electrically connected with con-
tact a¹, the current will also pass from contact a¹, to the contact b¹, thence through
armature M of the motor, to the contact 62, to the contact a², thence through the
field-magnet coil S, to the contact a³, 63, and out, thus energizing the motor and
causing it to operate in a direction to move the car upward for instance. As soon
as the push-button g, is released the circuit of the magnet coil e¹ is broken and
the armature E³, of the reversing switch assumes its normal intermediate position
between the magnets, breaking all the circuits of the motor, and the same result
will happen, of course, if the automatic stop switch F¹, is broken or a door in the
well is opened or the switch I, on the car or the door on the car is moved.
If it is desired to have the elevator car move in an opposite direction, pressing
any one of the push-buttons g', will close the circuit, so that the coil e, of the
reversing switch is energized and the armature E³, is moved so that the con-
tacts a-a³, engage respectively the contacts c³, and the circuits are substantially
the same as before, except that the current through the armature is reversed
causing the car to move in the opposite direction, and the car will so move as
long as the operator keeps the button compressed or until the circuit is broken
by the automatic stop motion switch or by the movement of a door or gate contact
or the switch I, on the car.
It will thus be seen that the operator must be in a position to see the car in
order to start it in the right direction by pressing the push-button g, or g¹, and to
stop it at the proper place. If perchance two buttons on two successive floors are
simultaneously closed the car would travel until both buttons were released or
until the circuit was broken by the switch I, the movement of a door or gate, or
by the automatic switch. In all cases when the circuit is broken not only is the
motor stopped but the brake is released and automatically applied and remains
so until the circuit is again closed.

page_text: he contacts c³, and when the magnet e¹, is energized the armature is moved
o bring the contacts a-a³, into engagement with the contacts b, b³.
Arranged in the circuit controlling the magnets e, e¹, which in the present
nstance is shown as a branch of the main line, although it may be an independent
ine receiving its current from an independent source, are the automatic stop
motion switches F, F', they being shown in the present instance diagrammatically
and they may be of any known or desired construction, they being arranged so
that one or the other will be operated as the car reaches the extremes of its move-
ment in the well in the usual manner.
The circuits are arranged as follows: Plus and minus indicate the leading-in
wires or circuit, and this is normally open, and each terminal has two contacts
as b, c, and b, c, co-operating respectively with the contacts a, a³, on the moving
armature E, of the reversing switch. The series field-magnet coil S, is shown
as connected to the contacts a², a³, of the armature of the reversing switch, while
the brake magnet circuit is connected between contacts a, a³, thereof. The
armature M, is shown with its terminals respectively connected with the con-
tacts b, and c¹, 2, on opposite sides of the moving armature, so that the
current through the armature of the motor will be reversed according as the
armature of the reversing switch is moved to one side or the other, while the circuit
through the field-magnet coil and brake magnet coil will remain unchanged in
direction. The coils e, e¹, of the reversing switch are connected by the conductor e³,
to the minus terminal of the circuit and from these coils, respectively, lead the
conductors e³, et, extending to the respective contacts g, g¹, of the switches G,
G1, G2, and when there is a switch upon the car branch circuits, as e5, e6, lead to
The push-buttons or
the contacts of the push-button or switch G³, on the car.
switches, while they may be of any desired construction, are shown as having
their movable contact pieces g, g', connected together and to the conductor e,
and in this conductor e, are shown contacts es, adapted to be operated by the
doors of the well, it being understood that when the doors are closed the circuit
through the conductor e, is closed, and, when any one of the doors is opened the
circuit is broken. Also arranged in the conductor e", is a resistance device H
shown as electric lamps and the terminal e³, of this conductor while shown detached
is supposed to be joined to the plus terminal of the leading-in conductor, or one
of the terminals of any other source of power, as a battery or the like. This
conductor e', includes a switch or button g³, on each floor, and also includes the
contacts elo, controlled by the door or gate on the car, and these push-buttons g³,
are normally closed, but when any one of them is operated the circuit is broken
through the magnets e, e¹, of the reversing switch, and the circuit of the motor
is consequently broken and the car can be brought to rest by manipulating either
one of these push-buttons g³.
Arranged in the circuits e³, et, are the magnets I and K, respectively, and
connected to the normally open and movable armatures I', K¹, thereof are branch
conductors ell, e12, connected to the conductor e', and including respectively the
coils of the magnets J, L.
The conductor e³, includes a pair of terminals e¹³, which are normally closed
by the armature L', of the magnet L, and the conductor et, includes a pair of
terminals e¹, normally closed by the armature J1, of the magnet J. These various
magnets are represented in a conventional form and may, of course, be of any
desired or usual construction which can operate to control the circuits in the
manner hereinafter described.
With this arrangement of circuits the operation will be easily understood by
those skilled in the art, and supposing for instance, that the elevator cage is at
the bottom of the shaft or at any other position below the upper floor and it is
desired to bring the elevator to the upper floor. Any one of the push-buttons g¹,
is pressed, as for instance the push-button g' at the upper floor, and the circuit
is then traced as follows: From the plus terminal, through the resistance H,
conductor e, it being understood that the contacts es, are closed through the

page_text: the door contacts and the stop push-buttons and two conductors, as e³, et, connected
respectively to all of the up and all of the down push-buttons and to the magnet
coils e, e¹, of the reversing switch, and included in these conductors are the mag-
nets I, K, which may be termed circuit-maintaining magnets, while in parallel
circuits therewith are the non-interfering magnets J L.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to us
by our foreign correspondents, we declare that what we claim is :-
-
In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of a single push-button for each floor or
station, and circuits and connections between the push-buttons and motor whereby
when any push-button is operated the circuit is closed and the motor operated to
bring the car to the station corresponding to the push-button, substantially as
described.
2. In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of a single push-button for each floor or
station, and circuits and connections between the push-buttons and the motor,
substantially as described, whereby when any one of the push-buttons is operated
the circuit is completed and the car brought to the desired station, and after the
closure of the circuit the operation of any of the other push-buttons will not
interfere with the movement of the car, as set forth.
3. In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of a single push-button for each floor or
station, circuits and connections between the push-buttons and motor whereby
when any push-button is closed the motor will be operated to bring the car to
the desired station, and means for automatically closing a circuit around said
push-buttons after one of them has been operated, thereby preventing interference
with the movements of the car, substantially as described.
4. In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of a single push-button for each floor or
station, circuits and connections whereby when any push-button is operated the cir-
cuit is closed between the car and the desired floor, and means in the push-button
circuit for short circuiting the push-buttons when any one is closed and thereby
preventing interference, substantially as described.
5. In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of a single push-button for each floor or
station, circuits and connections whereby when any push-button is operated the
circuit is closed between the car and the desired floor, and means in said push-
button circuit for short-circuiting and for breaking the circuit of the push-buttons
when any one of them is closed, substantially as described.
6. In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of a single push-button for each floor or
station, a circuit making magnet for each push-button circuit, and a circuit-
breaking magnet controlled thereby, whereby the push-button circuits are short
circuited and broken and interference prevented, substantially as described.
7. In an apparatus for controlling elevators, the combination with a motor for
operating the car in either direction, of an electric reversing switch, a floor con-
troller connected to operate the switch, a push-button for each floor, and a circuit
between each push-button and the floor controller, substantially as described.
8. In an apparatus for controlling elevators, the combination with a motor for
operating. the car in either direction, of an electric reversing switch, a floor con-
troller operated by the motor and controlling the reversing switch, a push-button
for each floor, a circuit between each push-button and the floor controller, and
means in said push-button circuit for closing a circuit around the push-buttons,
substantially as described.
9. In an apparatus for controlling elevators, the combination with a motor for

page_text: said magnets being included in circuits containing sets of two push-buttons,
substantially as described.
20. In a two-button system for the electrical operation of elevators, the combi-
nation with a motor, of a reversing switch controlling the circuits of the motor,
and coils in the switch connected with the main line circuit and including sets of
two push buttons, substantially as described.
21. In a two-button system for the electrical operation of elevators, the combi-
nation with a motor, of a brake, therefor, a reversing switch controlling the cir-
cuits of the motor and brake, coils included in the main circuit controlling the
switch, and sets of two push-buttons also included in the circuit controlling the
switch, substantially as described.
22. In a two-button system for the electrical operation of elevators, the combi-
nation with a motor, of a reversing switch controlling the circuits of the motor,
circuits connected with the reversing switch and including sets of two push-
buttons for controlling the switch, and a brake switch in the car also controlling
the circuits of the switch, substantially as described.
23. In a two-button system for the electrical operation of elevators, the combi-
nation with a motor, of a reversing switch controlling the circuits of the motor,
and a single branch circuit controlling the switch and including sets of two push-
buttons, substantially as described.
24. In a two-button system for the electrical operation of elevators, the combi-
nation with a motor, of a reversing switch controlling the motor, a circuit con-
nected to the switch and containing sets of two push buttons for controlling the
switch and automatic stop motion switches in the circuit controlled by the move-
ment of the elevator, substantially as described.
25. In a system for the electrical operation of elevators, the combination with
a motor and a reversing switch controlling the motor, of a circuit connected to
the switch and including two sets of buttons and circuit maintaining magnets,
substantially as described.
26. In a system for the electrical operation of elevators, the combination with
a motor and a reversing switch controlling the motor, of a circuit including two
scis of push-buttons, circuit-maintaining magnets, and non-interfering magnets
controlling said circuit, substantially as described.
27. In a system for the electrical operation of elevators, the combination with a
motor and a reversing switch controlling the motor, of a circuit connected to the
switch and containing two sets of push-buttons, circuit-maintaining magnets
included in said circuit, and non-interfering magnets included in branches of
said circuit, substantially as described.
28. In a system for the electrical operation of elevators, the combination with
a motor and a reversing switch controlling the motor, of a circuit connected to
the switch and containing two sets of push-buttons, circuit-maintaining magnets
included in said circuit, and non-interfering magnets in branches of said circuit
controlled by the circuit-maintaining magnets, substantially as described.
29. In a system for the electrical operation of elevators, the combination with
a motor and a reversing switch controlling the motor, of a circuit connected to
the switch and containing two sets of push-buttons, a branch of the circuit leading
from each set of push-buttons, and a circuit-maintaining magnet in each branch,
substantially as described.
30. In a system for the electrical operation of elevators, the combination with
a motor and a reversing switch controlling the motor, of a circuit connected to the
switch and containing two sets of push-buttons, a branch of the circuit leading
from each set of push-buttons, a circuit-maintaining magnet in each branch, and
a non-interfering magnet controlled by the circuit-maintaining magnet of each
branch and controlling the other branch, substantially as described.
31. In a system for the electrical operation of elevators, the combination with a
motor and a reversing switch controlling the motor, of a circuit connected to the
switch and containing two sets of push-buttons, a branch of the circuit leading