Improvements in Electrical Selectors and Answer-backs.
Year: 1896

page_text: Date of Application, 7th July, 1896-Accepted, 25th Sept., 1896
COMPLETE SPECIFICATION.
[Communicated from abroad by JOHN MOWE DRYSDALE, of the City of New
York, U.S.A.]
Improvements in Electrical Selectors and Answer-backs.
I THEODORE MCKENNA of 17 & 18 Basinghall Street in the City of London
Solicitor and Patent Agent, do hereby declare the nature of this invention and in
what inanner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
The invention is one which is included in the class known as selectors and is
designed to be used in cases where selectors can be applied; it is specifically described
in the following specification in connection with signalling devices, but it is obvious
that it is equally serviceable in the well known and general uses of selectors. A
part of the invention also consists in certain improvements in the answer backs or
that portion of the device which sends a return message to the calling station to
indicate that the call has been properly made.
The accompanying drawings illustrate the invention, of which
Figure 1 is a side elevation of the device with a portion of side wall removed.
Figure 2, an elevation of the opposite side of Figure 1 with upper part of side-
wall removed.
Figure 3 is a front elevation of the device.
Figure 4 a plan view of the front part of the instrument.
Figure 5 is a view of the brushes and the selector crank and pin which controls
them.
Figures 6 and 7 are enlarged perspective views of the combination and spacing
wheels and their operating mechanisms, showing different positions of the parts.
Figure 8 is a plan view of an answer-back device with its attachments for closing
a circuit to a signal.
Figure 9, a side view of the same.
Figure 10 is a diagram of the circuits showing conventional forms of the
apparatus.
Upon a suitable base as A are erected the standards or side-plates B, which
constitute the frame and support the mechanisms of the apparatus.
Journalled in the frame is the shaft which carries the wheels 1, 2, and 3 (see
Figures 6 and 7). I may be called the combination wheel as its teeth are cut thereon
in members, separated by a raised space and form a mechanical representation of a
predetermined arrangement or fixed combination of electrical impulses received from
a suitable transmitter. 2 may be called the spacing wheel, as its periphery is cut
and arranged to represent spaces between its members which correspond with the
teeth of the combination wheel, that is to say, where the teeth occur on one of the
wheels a raised space is placed upou the other, and both have a raised space in
common, at the end of each member of the combination; they are both rigidly
secured to the shaft and are operated by a single magnet in the manner hereinafter
described. 3 is a ratchet-wheel, also secured to the same shaft and is provided with
the check-pawl, which drops into one of the teeth at each impulse and retains the
shaft until it is thrown out by the operation of the devices; this wheel may therefore
be called the check-wheel. The wheels are impelled or thrust forward at each
impulse against the tension of a coiled spring, located within the drum 6, on the
shaft b; this spring exerts its tension to restore the selector to zero, when it has

page_text: completed its phase, or when a false impulse is received from the transmitting
instrument. C is an electro-magnet; c' a pivoted armature lever which responds to
electrical impulses through the coils of the magnet and is provided with the usual
retractile spring c³.
In the drawings there is shown a retarding device, represented by the wheel D
and the anchor d', the wheel is suitably mounted on a shaft properly journalled in
the frame. On the same shaft is placed a pinion d², which meshes with a pivoted
rack d³ upon the arm of this rack there is a pin d', which enters and plays in a
slot in the free end of the arm e; the other end of this arm is pivoted to the
armature lever c, as shown, so that the prompt movement of the parts is unaffected
by the retarding device pending the lost motion of the slot and pin, but it is brought
into action when either end of the slot contacts with the pin.
The impelling pawls e', e', are pivoted to the end of the armature lever and act
upon the combination and spacing-wheels 1 and 2 (see Figures 6 and 7); they are
arranged with a spring which exerts its tension to retain the pawl in contact with
the periphery of the wheels. As the wheels are impelled and turn the shaft 6', it is
checked and held by the checking-pawl 2, acting upon the check-wheel 3, and I have
provided means for throwing out this pawl, when a false impulse is transmitted or
when the impulses cease, and when this checking-pawl is thrown out the coiled
spring in the drum 3 will return the selector to zero or starting point. Within a
slot on the post F is pivoted the head-piece fat f2, whose spring retains the
head-piece inwardly until thrown out. This head-piece carries the bar f, and the
bar carries the projections, f. The upper arm of the head-piece is provided
with the pin which carries the cross-bar, which projects behind the pawls e', e²,
and are so arranged with each other that when the pawl el is dropped into a notch
on the wheel 1, and descends with the armature lever, both pawls e', e2 will pass
inside the projections f, f, but when that pawl is riding upon a raised space on
the wheel, which occurs when a false impulse is transmitted, it will strike the pro-
jection when it descends (as shown in Figure 7), throwing out the head f¹ and
cross-bar f, which in turn throws out both pawls e and e. This movement also
throws out the pawl 62 from the check-wheel 3, and allows the selector to be returned
to normal position. Projecting from the head-piece f¹ is a pin f, and from the
shaft 6, which carries the pawl 62 there is an arm 65 which lies in the path of the
pin, and as the head-piece is thrown out when the false impulse occurs the pawl b
is lifted and the wheel 3 released. The wheel 1 is cut to represent a predeter-
mined arrangement of impulses, for example, 4, 2, 1, 3, 2, and each of these require
a corresponding arrangement of impulses from the transmitter and may be called
the members of the combination. Between each member and the next adjoining one
there is a raised space on the wheel which represents a distance of two impulses, if
such were given, and then the next member of the combination begins, followed by
the raised space.
On the wheel 2 the spaces occur where the teeth are placed on
No. 1 with an increase to represent the two impulses of space on the wheel 1; and
teeth where the spaces occur on No. 1. The wheel 2 is a little smaller in diameter
than the wheel 1 so that its pawl may descend upon one of its spaces and still pass
inside of the projection 16, and the two are arranged together so that at the start
from normal position and at the beginning of each member of the combination both
of the pawls are in a notch upon the respective wheels.
The impulses from the transmitter must be given to correspond with the wheels,
and vary in the amount of pause between the impulses, and in these pauses the
armature lever goes back different distances according to the duration of the pauses,
as will be illustrated by taking the first member of the combination, which is 4, or
four impulses.
At the starting point both pawls are in a notch, the armature descends four times
in succession with sufficient rapidity to allow the pawi of wheel 1 to return and enter
the notch behind, but not further, and descend again, until the four impulses are
given both pawls pass within the projection f, f, pawl e' escapes because it is
within its notch, and pawl though riding on a space escapes the projection f

page_text: because of the smaller diameter of its wheel. When these four impulses are com-
pleted a pause occurs in the impulses sufficient to allow the armature lever to go
back a distance of two notches and thus pass over the space between the members.
At this point both pawls are in their notches and descend together propelling the
wheels; two impulses are given, then a pause sufficient to pass the pawls over the
space between the members, and so on. Now it will be seen that if this pause is too
short and the pawl descends before its time that e' will descend upon the raised space
on the wheel and throw out the check pawl &, releasing the wheel 3, which allows
the selector to be returned to zero. Again if five impulses are given instead of four
the same thing occurs, or if the pause is too long the pawl el will rest upon the
second or third notch of the next member of the combination, so that when the
impulses are given to suit the combination the same thing will occur, or else if
the armature be allowed to return too far it will of itself release the check-wheel in
the manner I will now describe:
The rack d' is provided with a sleeve d by which it is journalled on its shaft, and
on this sleeve and moving with the rack is the arm d, whose path is beneath the
extended arm of pawl 62. When the armature lever is down and engage in pro-
pelling the wheels the arm does not strike the pawls, but if the arm is allowed to go
back too far, either by allowing a pause of too long duration between the impulses
or when the impulses cease, the return of the armature lever causes the arm to
lift the check-pawl and return the selector to zero. In this way also the parts are
restored to normal when the solector has completed its phase.
When the selector has completed its phase a crank-pin on the shaft & closes the
brushes h, ' to control a circuit to perforin such work as is common and usual with
these devices which need not be further described.
In connection with a selector and to be used therewith, I have devised an improve-
ment in the answer-back illustrated in Figures 8, 9, and 10 of the drawings, which
I will now describe.
The general construction of an answer-hack needs no description, but in the
present device the electro-magnet K is provided with an armatura K, which in
normal position rests against the stop K' and is drawn away from said stop to the
core of the magnet K when an electrical current or impulse is transmitted through
its coils, and remains there until the current or impulse ceases, when it again
returns to its normal position: this armature is provided with a projection K.
The handle I is turned by hand against the tension of a spring, which operates
a suitable train. One of the wheels of the train is provided with a pawl which
acts upon a shaft carrying the wheel M to turn it in response to the spring.
Upon this wheel are the pins m', m2, at opposite sides, and these pins are caught
and held by the projection 3 on the armature, when in normal posision, and are
released when the armature is drawn to the magnet, each time allowing the wheel
to give one-half revolution. Upon the periphery of wheel M are cut or otherwise.
arranged two series of teeth occupying each one-half of its periphery, and these
teeth form the combinations which through the brush m³, transmit to the calling
station the message that the signal is set either at danger or safety. On the
same shaft with the wheel M is secured a disk which, in connection with its
brush me, is arranged to close a signal circuit. This disk turns with the shaft
and wheel, and is constructed as shown in Figure 8, one-half of insulating and
the other of conducting material, as shown at m, m: the brush ma riles upon
the edge of this wheel; when on the conductor it closes the signal circuit, and
when on the insulator opens the circuit.
On the frame are shown six binding-posts 1 2, 3, 4, 5, 6. Nos. 5 ani 6
are connected to the answer-back circuit; Nos. 3 and 4 to the circuits controlling
the magnets K, K.
The binding posts 1" and '2" are the terminals of the signal circuit: from
post 1 a wire leads to the shaft of the wheel M and disk, and the current runs
from a local battery not shown in the drawings through this wire to the disk,
thence to brush, thence to binding post 2, and thence to the other side of the

page_text: battery. Thus the binding-posts 1 and 2ª represent the signal circuit, 3 and 4*
the magnet circuit, 5 and 6 the answer-back circuit.
The operation of the device is as follows:
Suppose the answer-back is wound up and held by the pin m' and projection **
on the armature in the position shown in Figure 8, with the brush me resting on
the insulating part of the disk. This is its normal position and the signal not shown
in the drawings is at danger to take it out of this position and throw it to safety
it is necessary that the brush me should be transferred to the conducting part of
the wheel to close the signal-circuit through binding-post 1 and 2: this is
done by an electrical impulse through the coil of answer-back magnet K which
closes the circuit therethrough, drawing away the armature ; and the wheel and
disk begin to revolve. It will be noticed that on the wheel M there is a long
surface upon which brush m³ rests and the wheel beyond this long surface is pro-
vided with the teeth which transmit the answer-back message; before it has reached
these teeth the conducting part of the disk has reached the brush me, closing
the signal-circuit and throwing the signal to safety before the answer-back message
begins; the impulse which has released the projection on armature k, from the
pin m', having ceased, the armature returns to normal position with its projection
ready to catch pin m³, and when that pin is caught (the brush me resting on the
conducting part of the wheel) the signal is held in safety position until another
impulse through the magnet K releases the wheel and allows it to return to its
danger or normal position. Thus at each half revolution of the wheel, the signal
is set at either danger or safety and remains there until changed as described.
The train of this device may be arranged so that when wound any number of
revolutions of the wheel and disk may be given.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
1 claim is:
1. In an electric selecting instrument a movable device actuated by the armature
of an electro-magnet to the end of its phase in response to impulses from a
transmitter, means for retarding the backward throw of the armature between the
impulses thereby preventing it from completing its backward throw, and means
for returning the selector to zero actuated by the same armature in completing
its backward throw when the actuating impulses cease.
2. In an electric selecting instrument a movable device provided with a mechanical
representation of a predetermined arrangement of electrical impulses, and impelled
by mechanism responding to said impulses, in combination with a single electro-
magnet and its arinature lever, and means actuated thereby to impel the sector
and thereby work out the predetermined arrangement.
3. In an electric selecting instrument two wheels mounted upon a single shaft
having cut upon their respective peripheries a mechanical representation of a fixed
combination of electrical impulses, an electro-magnet and single armature lever
provided with pawls co-operating with the wheels, and means for working out the
combination, actuated electrical impulses representing the combination transmitted
through the coils of the magnet.
4. In an electric selecting instrument a movable device actuated by an electro-
magnet responding to electrical impulses transmitted through its coils, an armaturo
lever having a downward movement of given distance from starting point and two
backward movements both within said given distance for working out the com-
bination of the selector, one of said backward movements to return and catch the
next succeeding tooth of the wheel, and the other to return and catch the next
but one of the teeth, said movements governed by the duration of the pauses
between the electric impulses.
5. In an electric selecting instrument a movable device actuated by an electro-
magnet, responding to electrical impulses transmitted through its coils, an armature
lever having a downward movement and three backward movements for working

page_text: out the combination and restoring the instrument to zero at the end of its phase,.
said movements regulated by the duration of the pauses between the impulses.
6. In an electric selecting instrument two wheels mounted upon a single shaft
and cut upon their peripheries with notches and spaces forming a mechanical
representation of a fixed combination of electrical impulses, and means operated
by a single magnet to impel the wheels and work out the combination in response.
to the transmitted impulses.
7. In an electric selecting instrument a movable device responding to a fixed
combination of electrical impulses transmitted through the coils of an electro-
magnet, an armature lever and mechanical connection whereby the phase of the
selector is worked out, and means for restoring the instrument to zero actuated
by the forward throw of the armature lever and also by the backward throw of
said lever.
8. In an electric selecting instrument a movable phase-completing device actuated
by an armature lever responding to impulses through the coils of its magnet to
work out the combination, means for restoring the instrument to zero actuated
by a false impulse, and means for restoring to zero at the end of its phase, actuated
by the armature lever in returning to starting point.
9. In an electrical apparatus, an answer-back provided with a winding and
checking mechanism, in combination with circuit-closing devices connected there-
with and actuated thereby when released, means actuated by the movement of the
answer-back mechanism when released to first close a circuit and thereby actuate
a signal or other device, and then send a return message to line.
10. In an electrical apparatus, an answer-back provided with a spring for actuating
its mechanism and winding and checking devices, in combination with a shaft
turned by the spring when released, a wheel carried by said shaft provided with
means for actuating return message devices with each half turn thereof, and
devices actuated also by each half turn to set a signal or other device, substantially
as described.
Loted the 7th day of July 1896
THEO.
MCKENNA,
17 & 18 Basinghall Street, London..