IMPROVEMENTS IN MEANS FOR INDICATING AND REGULATING THE CURRENT OF ELECTRICAL GENERATORS FOR SUPPLYING ELECTRIC LIGHTS AND OTHER PURPOSES
Year: 1882

page_text: LETTERS PATENT to Thomas John Handford of No 42 Southampton Buildings
in the County of Middlesex Patent Agent, for an invention of "IMPROVEMENTS
IN MEANS FOR INDICATING AND REGULATING THE CURRENT OF ELECTRICAL
GENERATORS FOR SUPPLYING ELECTRIC LIGHTS AND OTHER PURPOSES"
A com-
munication from abroad by Thomas Alva Edison of Menlo Park in the State
of New Jersey United States of America.
PROVISIONAL SPECIFICATION left by the said Thomas John Handford at
the Office of the Commissioners of Patents on the 3rd March 1882.
«<
THOMAS JOHN HANDFORD of No. 42 Southampton Buildings in the County
Middlesex, Patent Agent IMPROVEMENTS IN MEANS FOR INDICATING AND
REGULATING THE CURRENT OF ELECTRICAL GENERATORS, FOR SUPPLYING ELECTRIC
LIGHTS AND OTHER PURPOSES A communication from abroad by Thomas Alva
Edison of Menlo Park, in the State of New Jersey-United States of America
"
The object of a portion of this invention is to produce devices to be used in
connection with dynamo or magneto electric machines and electric lights, which
will notify the engineer when the lights are above or below the desired limit of
candle power so that he can regulate the generative capacity of the machine or
machines in accordance therewith, and also to produce other devices which will
prevent injury to the machine or machines when an abnormally large current is
caused to flow by the addition of more lights than the plant has capacity to furnish,
and will at the same time notify the engineer of the condition of affairs.
"
These devices are especially adapted for use in isolated work" or with plants
for lighting separate buildings or small areas, and in connection with incandescing
electric lamps arranged in multiple arc
The first object is accomplished by arranging an electro-magnet in a derived or
multiple arc circuit from the main or consumption circuit, such magnet circuit

page_text: having many times more resistance than one of the lamp circuits, a wire or other
resistance being placed therein for that purpose-An incandescing lamp may
however be used for this resistance-In a shunt circuit around this resistance
are arranged the armature lever of the magnet and a vibrating bell.
The free end of the armature lever plays between two contacts, the making of
each of which completes a circuit through the bell hammer vibrator.
Between the armature lever and the front contact is a yielding stop which may
be an arm held back against a fixed pin by a spring.
This yielding step arm determines the central position of the armature lever―
One of these bell circuits has considerably more resistance than the other, so that
alarms varying noticeably in their loudness will be produced.
When the lamps are within the fixed limits of candle power, the magnet will
attract the lever sufficiently against the retractile force of its spring to separate it
from the back contact and will hold it forward against the spring stop arm so as
to open the bell circuit.
Now if the current increases so as to raise the lamps above the limit of candle
power, the armature lever will be attracted by the magnet and will overcome the
spring stop arm and force the same against the front contact, completing the bell
circuit through a definite resistance and causing a loud alarm to be sounded which
will continue until the engineer regulates the generator or generators, so as to
reduce the candle power of the lights.
If the lights drop below the limit of candle power, the magnet will at the same
time be weakened, and the lever will make the back contact-This completes the
bell circuit through greater resistance than when the front contact is made and a
continuous alarm will be sounded which will be noticeably feebler than in the
instance first, described-As soon as the lights are brought up to the required
degree of luminosity, the alarm will cease to sound, the bell circuit being broken
by the attraction of the lever to a central position against the spring.
For regulating the machine, it is preferred to use an adjustable resistance placed
in the field circuit, which may be derived from the main conductors supplied by
the machine; or the commutator brushes can be adjusted for this purpose.
It is evident that instead of using a single vibrating bell with two circuits
having different resistance, two bells may be used, in which case the bell circuits
may have different resistances, or the circuits may have the same resistance and
the bells be constructed to give sounds of different pitch, or both features may be
combined.
Instead of bell alarms alone, an indicator may be used consisting of a pointer
travelling upon a scale to right or left and operated by the armature lever of the
electro magnet in the multiple arc circuit: and in connection with the indicator an
alarm may be arranged to strike when the pointer reaches a certain point on
either side of its normal position-lt is also evident that the resistance-coils in the
multiple arc circuit may be dispensed with, and the magnet itself made of
sufficiently high resistance, the armature lever making and breaking circuit to
suitable alarms; also that the wire instead of being coiled around a magnet may
be arranged as a galvanometer or with a heavy magnetized needle provided with
arm and retractor: also that the wire may be wound as two spools, one attracting
the other, after the manner of an electro-dynamometer.
The second object is accomplished in the following manner :-
A piece of safety catch wire or material is placed in one of the conductors of the
main or consumption circuit.
This safety catch is of such size and character, that when more lamps are put
in circuit, than the plant is designed to furnish, and before the machine or
machines are injured by the abnormally large flow of current, it will burn out
and break the circuit between the generator and the translating devices-In a
shunt around this safety catch are arranged a vibrating bell and a resistance, the

page_text: resistance being sufficient to prevent the striking of the bell when the safety
catch is intact, but when the safety catch is burnt out, the current passes through
the bell circuit and operates the bell hammer.
The lights at the same time drop to a red heat-The engineer then removes a
sufficient number of lamps and replaces the safety-catch.
The two classes of alarms above described are useful with other translating
devices besides lamps to show corresponding conditions-Another portion of this
invention relates to means for automatically varying the resistance of the field
circuit of a dynamo or magneto electric machine for the purpose of regulating the
generation of current by the machine; the object had in view being to produce a
continuously acting mechanism for this purpose, and one in which the increase or
decrease of resistance is not limited by the movement necessarily sinall of the
armatures of electro-magnets.
Generally speaking the arrangement is as follows:-
In the field circuit of a dynamo or magneto electric machine is placed a circular
adjustable resistance, having its contact points arranged inside, portions of the
resistance being cut in and out by a contact arm forming part of the circuit and
pivoted in the centre of the resistance-The contact arm is turned by ratchet
wheels, one adapted to be moved by a pawl in one direction the other by another
pawl in the opposite direction, so that resistance is placed in or thrown out of
circuit as one or the other pawl is in operation-Each pawl is moved by the
vibrating armature of an electro-magnet there being a magnet and armature for
each pawl-To effect the make and break of circuit which causes the vibration of
the armature, one end of the latter extends between the sides of a pivoted U-shaped
piece which is driven by the movement of the armature in one direction to
complete the circuit, and in the other direction to break it, the U-piece being
weighted so that the motion is assisted by gravity; or a spring may be used for
this purpose.
Each of the electro-magnets operating these vibrating armatures is placed in a
circuit which is a division of a shunt circuit from a multiple arc circuit, the last
containing an electro-magnet, and a resistance for turning current into the shunt.
The pivoted spring armature of this magnet forms a part of the shunt circuit,
and its free end is placed between contact points.
A pivoted spring arm is also placed between these contact points in such
manner that the forward movement of the armature forces it against one of them
and completes one of the divisions of the shunt circuit, while the armature when
drawn back a sufficient distance strikes the other contact point and completes the
other division.
Normally however the armature and spring arm, are held by the resilience of
their springs, and by a properly placed stop, midway between the contact points,
and either circuit is completed only by an increase or decrease in the force of the
electro magnet.
When too much current is in the main circuit it is desirable to decrease the
generative capacity of the machine by placing more resistance in the field circuit-
The magnet in the multiple arc circuit of course has its energy increased by the
excessive amount of current in the main line, and attracts its armature, which
pushes the spring arm against a contact point, thus closing a division of the shunt
including one of the first mentioned electro-magnets, whose vibrating armature is
set in motion moving the pawl and turning the ratchet wheel and contact arm in
such a direction that more resistance is placed in the field circuit.
The current in the main circuit then decreases, and the magnet in the multiple
arc circuit weakens in power until the armature is drawn away by the spring, and
the circuit of the electro-magnet which actuates the contact arin is broken.
But if the current is very much decreased so that it becomes necessary to throw
out resistance, the first armature lever is drawn back by its spring and closes the
other division of the shunt circuit, through the other electro-magnet, whose pawl

page_text: arm turns the contact arm in the opposite direction and throws out a portion of
the resistance.
The above described mechanism possesses an advantage, new to automatic
systems of regulation videlicet: that any desired amount of resistance may be
thrown into or taken out of the field circuit, instead of only a small amount,
limited in extent by the play of the armature-lever, the variation of resistance
being accomplished by a continued movement of the mechanism, instead of by a
single impulse.
It is evident that this invention is equally applicable to magneto and to dynamo
electric-machines; and to a battery or number of machines, as well as to a single
machine.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas John Handford in the Great Seal Patent Office on the
2nd September 1882.
AND
THOMAS JOHN HANDFORD of No 42 Southampton Buildings in the County
of Middlesex Patent Agent-" IMPROVEMENTS IN MEANS FOR INDICATING
REGULATING THE CURRENT OF ELECTRICAL GENERATORS FOR SUPPLYING ELECTRIC
LIGHTS AND OTHER PURPOSES' A communication from abroad by Thomas Alva
Edison of Menlo Park in the State of New Jersey United States of America
33
The said Invention relates first to devices to be used in connection with dynamo
or magneto electric machines having a multiple arc field circuit and supplying
electric lamps located in derived or multiple arc circuits, which devices will notify
the engineer when the lights are above or below the desired limit of candle power
so that he can regulate the generative capacity of the machine or machines in
accordance therewith
These devices are constructed and arranged in the following manner: viz:
An electro-magnet is employed arranged in a derived or multiple are circuit
from the main or consumption circuit such magnet circuit having many times
more resistance than one of the lamp circuits for which purpose a wire or other
resistance is placed therein or an incandescing lamp may be used for this
resistance. In a shunt circuit around this resistance are arranged the armature
lever of the magnet and a vibrating bell
The free end of the armature lever plays between two contacts the making of
each of which completes a circuit through the bell-hammer vibrator. Between the
armature lever and the front contact is a yielding stop which may be an arm held
back against a fixed pin by a spring. This yielding stop arin determines the
central position of the armature lever
One of these bell circuits has considerably more resistance than the other so that
alarms varying noticeably in their loudness will be produced
When the lamps are within the fixed limits of candle power, the magnet will
attract the lever sufficiently against the retractile force of its spring to separate it
from the back contact and will hold it forward against the spring top arm so as to
open the bell circuit
Now if the current increases so as to raise the lamps above the limit of candle
power, the armature lever will be attracted by the magnet and will overcome the
spring stop arm, and force the same against the front contact, completing the bell
circuit through a definite resistance and causing a loud alarm to be sounded which
will continue until the engineer regulates the generator or generators so as to
reduce the candle power of the lights
If the lights drop below the limit of candle power, the magnet will at the saine
time be weakened and the lever will make the back contact, This completes the
bell circuit through greater resistance than when the front contact is made and a
continuous alarm will be sounded which will be noticeably feebler than in the
instance first described. As soon as the lights are brought up to the required
degree of luminosity, the alarm will cease to sound the bell circuit being broken by
the attraction of the lever to a central position against the spring
For regulating the machine it is preferred to use an adjustable resistance placed
in the field circuit which is derived from the main conductors supplied by the
machine or the commutator brushes can be adjusted for this purpose
It is evident that in lieu of using a single vibrating bell with two circuits
having different resistances, two bells may be used in which case the bell circuits
may have different resistances or the circuits may have the same resistance and
the bells be constructed to give sounds of different pitch or both features may be
combined

page_text: The said invention relates secondly to devices which will prevent injury to the
machine or machines when an abnormally large current is caused to flow by the
addition of more lights than the plant has capacity to furnish and will at the same
time notify the engineer of the condition of affairs
This result is accomplished in the following manner :-
A piece of safety catch wire or material is placed in one of the conductors of the
main or consumption circuit. This safety catch is of such size and character that
when more lamps are put in circuit than the plant is designed to furnish and before
the machine or machines are injured by the abnormally large flow of current, it
will burn out and break the circuit between the generator and the translating
devices
In a shunt around this safety catch are arranged a vibrating bell and a
resistance the resistance being sufficient to prevent the striking of the bell when
the safety catch is intact, but when the safety catch is burnt out the current passes
through the bell circuit and operates the bell hammer. The lights at the same time
drop to a red heat. The engineer then removes a sufficient number of lamps and
replaces the safety catch
In the specification to former letters patent granted to the said Thomas Alva
Edison dated the 3rd of January 1880 No 33 there is described the interpolation of
a fusible wire between the generator and translating devices which would act as a
"safety catch
to prevent the capacity of the plant from being exceeded but this
invention involves the additional feature of an alarm which sounds when the
"safety catch" is burnt out
"
The said invention relates thirdly to means for automatically varying the
resistance of the field circuit of a dynamo or magneto electric machine for the
purpose of regulating the generation of current by such machine
This part of the invention is carried out in the following manner :-
In the field circuit of a dynamo or magneto electric machine is placed a circular
adjustable resistance having its contact points arranged inside portions of the
resistance being cut in and out by a contact arm forming part of the circuit and
pivoted in the centre of the resistance. The contact arm is turned by ratchet
wheels, one adapted to be moved by a pawl in one direction, the other by another
pawl in the opposite direction so that resistance is placed in or thrown out of
circuit as one or the other pawl is in operation. Each pawl is moved by the
vibrating armature of an electro-magnet there being a magnet and armature
for each pawl In order to effect the make and break of circuit which
causes the vibration of the armature, one end of the latter extends between
the sides of a pivoted Ushaped piece which is driven by the movement of the
armature in one direction to complete the circuit and in the other direction to
break it, the U piece being weighted so that the motion is assisted by gravity; or
a spring may be used for this purpose
Each of the electro-magnets operating these vibrating armatures is placed in a
circuit which is a division of a shunt circuit from a multiple arc circuit, the last
containing an electro-magnet and a resistance for turning current into the shunt.
The pivoted spring armature of this magnet forms a part of the shunt circuit, and
its free end is placed between contact points. A pivoted spring arm is also placed
between these contact points. in such manner that the forward movement of the
armature forces it against one of them and completes one of the divisions of the
shunt circuit, whilst the armature when drawn back a sufficient distance strikes
the other contact point and completes the other division
Normally however the armature and spring arm are held by the resilience of
their springs and by a properly placed stop midway between the contact points,
and either circuit is completed only by an increase or decrease in the force of the
electro magnet
When too much current is in the main circuit, it is desirable to decrease the
generative capacity of the machine by placing more resistance in the field circuit,

page_text: The magnet in the multiple are circuit of course has its energy increased by the
excessive amount of current in the main line, and attracts its armature which
pushes the spring arm against a contact point, thus closing a division of the shunt,
including one of the first mentioned electro magnets, whose vibrating armature is
set in motion moving the pawl and turning the ratchet wheel and contact arm in
such a direction that more resistance is placed in the field circuit. The current in
the main circuit then decreases and the magnet in the multiple are circuit weakens
in power until the armature is drawn away by the spring and the circuit of the
electro magnet which actuates the contact arm is broken
But if the current is very much decreased so that it becomes necessary to throw
out resistance, the first armature lever is drawn back by its spring and closes the
other division of the shunt circuit through the other electro-magnet, whose pawl.
arm turns the contact arm in the opposite direction and throws out a portion of
the resistance
It is evident that this invention is equally applicable to magneto and to dynamo
electric machines and to a battery or number of machines as well as to a single
machine.
And in order that the said Invention may be perfectly understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the accompanying two sheets of drawings
In Figure 1, (Sheet 1) and figures 2. 3 and 4 (Sheet 2) are respectively
indicated partly diagrammatically and partly constructively several modes of
carrying out the first part of the said Invention. The means for carrying out the
second part of the said Invention are illustrated in Figure 1 only-Figure 5
(Sheet 1) illustrates a mode of carrying out the third part of the said Invention
Referring to Figure 1 on the left hand side of which is illustrated devices for
notifying when the lights are above or below the desired limit of candle power,
A represents a dynamo or magneto electric machine 1. 2, the main or consumption
circuit and a a incandescing lamps in multiple arc or derived circuits 3, 4 represents
a multiple arc or derived circuit from 1, 2, with resistance R and the coils of an
electro magnet B placed therein the resistance being many times more than that of
one of the lamp circuits. From 3, 4 is a shunt 5, 6. around the resistance R. The
armature lever C. retracted by spring b is in this circuit. Front and back contacts
c, c are connected with the spring d of the vibrating bell mechanism which
consists of an electro-magnet e. an armature lever f. forming the bell hammer and
a gong g, the making of each of which contacts completes the circuit through the
bell hammer vibrator Resistances R¹ R2 are arranged in the bell circuit resistance R¹
being in the circuit of each contact c c¹ whilst R2 is only in the circuit of the back
contact c¹. so that alarms varying noticeably in their loudness will be produced.
A yielding stop arm C is placed between lever C and front contact c, and is drawn
back by a spring b' against a fixed pin 6. this yielding stop (the use of which is
of considerable importance) determining the central position of the armature lever.
R represents resistance in the field circuit 9, 10 which resistance is cut in and out
of circuit by the act of moving the lever r. in one direction or the other
When the lamps are at the normal candle power, the magnet B. will not he
strong enough to overcome both retractile springs 6 and 61; and the lever C will
stand in a central position, held against the stop arm C. and keeping open both
circuits through the bell mechanism as shewn in the drawing. Any increase in
the electro motive force that will raise the lamps to higher incandescence, will
strengthen B, which will attract C. and force C₁. upon contact c, completing the
circuit of lower resistance through the vibrating bell and causing it to strike a loud
alarm
The operator will then move the lever r so as to throw resistance into the field
circuit 9, 10, or regulate the machine in any other known manner and produce the
normal condition of the current when B will weaken allowing C to again assume a
central position, breaking the bell circuit. When there is a drop in the electro-
motive force and the lamps are reduced in candle power the magnet B will further

page_text: weaken, and the spring b will draw it against contact c¹. closing the circuit of
higher resistance through the bell mechanism and causing it to strike a noticeably
weaker alarm than when the circuit is closed at contact c
The operator then moves lever r throwing resistance out of the field circuit or
otherwise regulates the machine in any known manner and increases the electro-
motive force to the normal condition, when C will again assume a central position
as shewn in the drawing breaking the circuit of the bell mechanism
In figure 2 (Sheet 2) two bell mechanisms are shewn in the circuit of one of
which is a resistance R'. so that it will give a weaker sound than the other although
this resistance may be dispensed with and the bells themselves be constructed to
give different sounds. The operation is similar to that herein before described, with
reference to figure 1. and the same letters of reference denote corresponding parts
which have already been described in connection with figure 1
In lieu of employing bell alarms alone an indicator may be used consisting of a
pointer travelling upon a scale to right or left and operated by the armature lever
of the electro magnet in the multiple arc circuit and in connection with the
indicator an alarm may be arranged to strike when the pointer reaches a certain
point on either side of its normal position.
This modification is illustrated in Figure 3 (Sheet 2) in which d³ represents the
pointer travelling on a scale e¹. This pointer is secured to a turning shaft f'. which
is connected by a cord g¹ wound thereon with the upper end of the armature
lever C. A spring h¹ draws the pointer in the direction opposite to that to which
it is moved by the cord g'. The pointer will indicate the fluctuations of the
armature lever between the contacts. Springs oppose each other in their
action on the lever C and hold it normally in a central position. This device may
be used in place of the spring arm C¹ and stop b². shewn in figure 1.
The apparatus may be otherwise modified whilst still retaining the arrangement of
the controlling electro-magnet located in a multiple are circuit and its appurtenances
as herein before described. For example a device similar to a galvanometer may be
employed to make and break the alarm circuits as illustrated in Fig 4. In the
modification shewn in this figure the lever C closes at contacts c and c' circuits
through two sets of coils d² e². Within these is pivoted a heavy magnetized
needle the movement of which makes and breaks the alarm circuits at the
wire 7 from the needle being common to both circuits
I have shewn the arrangements Figs 3 and 4 as modifications embodying the
principles of the said Invention which may be used if found desirable but the
arrangements herein before described with reference to Fig 1 or the modification
thereof illustrated in Figure 2 will generally be found most suitable for the majority
of cases
On the right hand side of Figure 1 (Sheet 1) are shown devices arranged
according to the said Invention for preventing injury to the machine when an
abnormally large current is caused to flow by the addition of more lights than the
plant has capacity to furnish and notifying the engineer of the condition of affairs.
In this figure D is a piece of safety catch wire or material placed in 1 or 2 (it
being shewn as placed in 2 in the example illustrated) between the lamps and the
machine A. This safety catch is of such size and character, that when more lamps
are put in circuit than the plant is designed to furnish and before the machine or
machines are injured by the abnormally large flow of current it will burn out and
break the circuit between the generator and the translating devices. In a shunt 7. 8
around D. are arranged a resistance R³ and a vibrating bell, composed of an electro
magnet h, a spring i, a bell hammer k and a gong -When the safety catch D is
intact little or no current passes through the shunt circuit 7, 8, and the bell
mechanism is not operated, the resistance being sufficient under normal conditions
to prevent its action. An abnormal and dangerous flow of current will burn out the
safety catch when the current will be thrown through the bell mechanism and will
operate the same giving an alarm. If the abnormal flow of current is caused by a
larger number of lamps than the machine is intended to carry the operator will

page_text: remove or break the circuits of a number of lamps and will then replace the safety
catch.
The two classes of alarms or apparatus herein before described forming the subject
of the first and second parts of the said invention are especially adapted for use in
"isolated work" or with plant for lighting separate buildings or small areas but
they are also useful with other translating devices besides lamps to shew corres-
ponding conditions.
The third part of the said Invention which relates to means for automatically
varying the resistance of the field circuit of a dynamo or magneto electric machine
for the purpose of regulating the generation of current by the machine is illustrated
diagrammatically on Figure 5 (Sheet 1) of the drawings.
A, is a dynamo electric machine from which lead the main conductors 1, 2. of a
multiple arc system, 3, 4 is a multiple are circuit including the field magnets of the
dynamo, The wire 4 includes the circular adjustable resistance B while the wire 3
terminates in a pivoted contact arm a adapted to make contact with the points bb
of the resistance B.
5, 6 is another multiple are circuit including an electro-magnet C and a resistance D.
Around the latter is formed a shunt circuit 7, 8 which is divided into two
circuits 9x, c and 9 x'd; c and d being contact points
Either or both of the wires 7, 8 may if desired, be made adjustable so that they
may be connected with different parts of the resistance D and thus shunt more or
less current into the circuit 7. 8.
The magnet C is provided with an armature E pivoted at e and forming part of
the circuit 7. 8. At its free end it is provided with two contact points one on. each
side.
The armature has also a spring f whose tendency is to withdraw it from the
magnet C. A pivoted spring arm g is so placed that normally it is midway between
c and d being prevented from moving in one direction by a stop y, but it may be
pressed over by the armature so as to contact with c and close the circuit 9 x, c.
When the pressure is removed the current is broken and the armature E assumes
and is retained in a central position until the magnet becomes so weak that the
armature is drawn back against d, and closes the circuit 9, x' d.
The circuit 9 c includes a magnet F. having an armature G pivoted at h and
retracted by a spring i
The lower end of the armature enters between the sides of the U shaped metal
piece which is pivoted at 7 and placed between stops m n The wire x is attached
at l. and the wire 9 to the stop n so that when his thrown against n the circuit 9 x, c
is closed at this point and when it is thrown against m, the circuit 9, x, c, is opened
A ball or weight o assists the motion of the piece k. Thus the movement of the
armature G causes the make and break of circuit and the armature is made to
vibrate.
At the other end of the armature G is pivoted a pawl H which when the
armature G vibrates moves the rachet wheel and turns the contact arm a so that
it places more of the resistance B in the circuit 3. 4.
A similar arrangement is placed on the opposite side of the resistance F¹ being
the magnet G¹ its armature pivoted at h¹; k the U shaped circuit reverser
, l, m, n, o', parts corresponding to the parts ilm no respectively hereinbefore
described as appertaining to the circuit 9 x. cand H' the pawl actuating the ratchet
wheel r. so that the contact arm a is turned the opposite direction and cuts out
instead of putting in resistance
The apparatus operates in the following manner viz :-
When the current is normal and the candle power of the lamps is at the desired
point, the lever E will be held in a central position by the means herein before
described breaking both divisions of the shunt circuit 7. 8. An increase in the
electromotive force of the current will cause the magnet C to draw the armature
lever E against the contact c completing the division of the shunt through the
magnet F. Lever G will then be vibrated the circuit being alternately made and
broken by the retractile force of the spring i and the attraction of the magnet acting

page_text: on the lever G and through it on the U shaped piece k. The pawl H being thus
actuated the contact arm a is moved so as to throw resistance into the field
circuit.
The normal electromotive force having been restored magnet C weakens, and
lever E assumes a central position and the vibrating apparatus will be at rest.
When there is a decrease in the electromotive force magnet C will further weaken
allowing E to make contact with d and closing the circuit through F¹. Lever G¹
will be vibrated in a similar manner to lever G as herein before described moving
arm a in the opposite direction, and cutting resistance out of the field circuit, This
is the position of the parts indicated in the drawing the pawl H having advanced
acting upon the ratchet wheel ', after which it will be drawn back by means of
the spring acting upon the lever G' and the circuit being by this act, again
established the pawl will be again advanced and so on in succession until the
normal electromotive force is restored when the lever E will again assume a central
position and the vibrating apparatus will be at rest
It should be observed that the employment of devices for maintaining the lever E
of the controlling magnet in a central position when the electromotive force is
normal is a feature of considerable importance in this mechanism as without such
devices it is impossible to prevent the lights from flickering owing to the incessant
vibration of the said lever
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the same is or may be used or carried into effect
I would observe in conclusion that what I consider to be novel and original
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is :-
1st The combination with one or more electrical generators having a multiple
arc field circuit, and supplying lamps or other translating devices located in derived
or multiple arc circuits, of an alarm or indicator operated by the current generated
and indicating variations of candle power above or below or both above and below
the desired limit such alarm or indicator being controlled by an electromagnet also
located in a multiple are circuit and the several parts of the apparatus being
arranged and combined so as to operate substantially in the manner herein before
described
2nd. The combination with a safety catch between the translating devices and
the generater or generators of an electrically operated alarm arranged to be
sounded when the main circuit is opened by the safety catch substantially as herein-
before described
3rd The double vibrating mechanism controlled by an electro magnet located in
a derived or multiple arc circuit for throwing resistance into and out of the field
circuit of a dynamo or Magneto-Electric machine or a battery or number of such
machines supplying lamps or other translating devices arranged in multiple arc
substantially as herein before described with reference to Figure 5. of the accom-
panying drawings
In witness whereof I the said Thomas John Handford have to this my
Specification set my hand and seal this second day of September in the year
of our Lord One thousand eight hundred and eighty two.