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Dec. 24, 1946.
A‘ H_ SWANSON
2,413,120
MEASURING AND CONTROLLING APPARATUS
Filed Oct. 5:, 1942
INVENTOR.
ARTHUR H SWANSON
Patented Dec. 24, 1946
2,413,120
UNITED STATES PATENT'OFFICE
2,413,120
MEASURING AND CONTROLLING
APPARATUS
Arthur H. Swanson, Lafayette Hill, Pa., assignor
to The Brown Instrument Company, Philadel
phia, Pa., a corporation of Pennsylvania
Application October 8, 1942, Serial No. 461,267
11 Claims.
This invention broadly relates to control sys
terns and more particularly to systems for meas
uring, exhibiting and/or controlling a variable‘
condition such as temperature.
.
(Cl. 172—-239)
2
the reversible electric motor It assumes positions '
corresponding to the value of the temperature
condition existing within the furnace II. The
reversible electric motor It operates a screw shaft
One object’ of this invention is to provide a 5 I 5 which reciprocates a carriage IS. The carriage
novel control system for a multiphase reversible
I6 carries a contact I04 which slidably engages a
electric motor. In this respect the reversible
electric motor may be controlled by transformer
means having a pair of primaries to which alter
resistance I03. The carriage l8 reclprocated by
means to cause operation of the reversible elec
tric motor in one direction or the other.
dition. A stylus or pen l8 records the value of
the temperature condition on a continuously
reversible electric motor I4 assumes positions
corresponding to the value of the temperature
nating potentials of variable relative magnitudes 10 condition existing within the furnace H and,
are applied to energize oppositely the transformer
therefore, acts to exhibit the value of that con
Further objects of the invention are to provide
moving chart 20. The carriage l6 alsooperates
follow-up or rebalancing means in the control 15 a contact 2 I with respect to a pair of contacts 22
system, to control the system in accordance with
and 23 for controlling the operation of a re
the value of a variable condition and to measure,
versible electric motor 24 which in turn positions
exhibit and/or control the variable condition by
a valve 25 in the fuel line 26 leading to the fur
the control system.
nace II. The contacts 22 and 23 may be ad
Another object of this invention is to provide 20 justed for predetermining the temperature con
a novel condition responsive device which ‘may
dition to v,be maintained within the furnace II.
take the form of an'electronic discharge device
The temperature responsive device 80 is an
directly responsive to the value of the variable
condition and which may be advantageously uti
lized in the aforementioned control system.
The various features of novelty which charac—
terize this invention are pointed out with particu
larity in the claims annexed to and forming a
part of this speci?cation. For a better under
standing of the invention, however, its advan
electronic discharge device having an envelope
containing a cathode ll, a cathode heater 82, a
‘ control grid 03, and an anode 84. The cathode
' BI is subjected to the temperature condition with
in the furnace II and emits electrons in accord~
ance with the temperature condition prevailing
within the furnace II. This electron emission
30 by the cathode II varies the conductance from
tages and speci?c objects obtained with its use,
the anode to the cathode in accordance with the
referenceshould be had to the accompanying I‘ temperature condition in the furnace l I.
drawing and descriptive matter in which is 11
As shown, power is supplied to the cathode
lustrated and described a preferred embodiment
heater 82 by meansoi' a transformer 85 having
of the invention.
35 a primary 86 connected across the line wires 4!
Of the drawing:
v
and 42 and a secondary 81 connected to the
Fig. 1 is a diagrammatic illustration of one form
cathode heater 82. A rheostat 88 in series with
of the invention;
'
the cathode heater 82 may be utilized for regu
Fig. 2 illustrates diagrammatically another
lating the heating effect of the cathode heater
form of the invention which differs from Figure 40 82. If there is any possibility of voltage ?uctu
1 by utilizing another form of condition respon
ation in the supply lines 4| and 42 this may be
sive device.
'
Referring now to Fig. 1, a condition responsive
device in the form of a device responsive to tem
perature conditions is generally designated at 80
and is so located that it responds to a tempera
ture condition within a furnace II. The con
dition responsive device 80 controls the applica
remedied by making the transformer 85 a con
stant voltage transformer or by substituting a
battery for the transformer 85.
The cathode heater 82 is utilized for partially
heating the cathode 8|. The main supply of heat
for the cathode Bl comes from the temperature
condition withinathe furnace H. The arrange
tion of an alternating potential to a transformer
ment of Figure 1 while capable of responding to
means generally designated at I2 which in turn 50 temperature conditions generally in the furnace
applies an alternating potential to an electronic
II is particularly adaptable for use as a radia
ampli?er l3. The amplified alternating poten
tion responsive instrument and has been so illus
tial from the ampli?er I3 is applied to a multi
trated in Fig. 1. Located within the furnace H,
phase reversible electric motor generally desig
in Fig. 1, is a mass 90 being heated. Radiation
nated at H, and as will be pointed out hereafter, 55 from the mass 90 is ‘in accordance with the tem
‘2,413,1ao
3
4
traced from the line wire 4| through conductor
cathode 8|. The contact I04 is connected to the
age to produce a potential drop across the con
perature thereof. Radiant energy from the mass
trol winding 38 which lags the potential drop
passes through an opening 9| in the wall of the
across the power winding 31 to energize the re
furnace II and is focussed by a lens system 92
versible motor I4 for rotation in a direction to
on the cathode 8|. The cathode 8| is, therefore,
heated by radiant energy emanating from the C21 move the carriage I6 to the right. Upon ‘a de
crease in the temperature condition within the
mass 90 and is heated in accordance with the
furnace II the current flow through the sec
temperature of the mass 90. The amount of elec
ondary 34 predominates over that in'the second
tron emission by the cathode 8| is, therefore,
ary 36 to apply a signal to the electronic ampli
proportional to the temperature of the mass 90.
The transformer means generally designated at 10 ?er I3 which is 180° out of phase with the line
voltage. This produces a potential drop across
I2 includes a pair of transformers,‘ one of the
the control winding 38 which leads the potential
pair having a primary 33 and a secondary 34
drop across the power winding 31 to rotate the
and the other of the pair having a primary 35
reversible electric motor I4 in the opposite di
and a secondary 36. The multiphase reversible
electric motor I4 includes a power winding 31, 15 rection and to move the carriage I6 to the left.
Follow-up or rebalancing control is accom
a control winding 38, and a rotor 33.
plished in Fig. 1 by varying the potential of the
An alternating potential is applied to the con
grid 83 .to restore the current flow induced in
trol system by line wires 4| and 42 leading from
the secondary 36 to a value which is equal and
a source of alternating potential not shown. As
sumethat during the ?rst half cycle the line 20 opposite to the current flow in the secondary 34.
In this connection a battery I02 is utilized to
wire 4| is positive with respect to the line wire
place a potential drop across the resistance I03
42 and that conditions are reversed on the second
which is engaged by the contact I04 operated by
half cycle.
the carriage I6. The left end of the resistance
The transformer primary 35, as shown, is in
cluded in the output circuit of the electronic tem 25 I03 is positive with respect to the right end and
is connected by conductors 96 and I05 to the
perature responsive device 80 which may be
grid 83 by conductor I06. The battery I02 op
erating through the resistance I03 and contact
wire 42. During the ?rst half cycle a pulse of 30 I04 places a negative potential on the grid 83
which potential is dependent upon the position
current through the output circuit is applied to
of the contact I04 with respect to the resist
the primary 35 to induce a current ?ow in the
ance I03.
secondary 36 in the upward direction as is illus
When the temperature condition in the fur
trated by'the arrow in Fig. 1. During the second
95, anode 84, cathode 8|, conductors 96 and 37,
transformer primary 35 and conductor 98 to line
half cycle the electronic temperature responsive
device 80 does not conduct but due to the con
35 nace I I increases to increase the current flow in
struction of the transformer means I2 a current
duced in the secondary 36 the carriage I6 is
moved to the right to place a more negative po
tential on the grid 83. This reduces the current
flow is produced in the opposite direction in the
flow induced in the secondary 36 and when the
secondary 36. The primary 33 is included in a
circuit extending from the line wire 4| through 40 current flow in the secondary 36 becomes equal
and opposite to the current flow in the secondary
the rheostat I00, primary 33 and conductor 98
33 rotation of the reversible electric motor I4 is
to line wire 42. During the ?rst half cycle a
stopped. Likewise, when the temperature within
current ?ow is induced in the secondary 33 in
a downward direction as illustrated by the arrow
in Fig. 1 and during the second half cycle this
current ?ow is reversed. The current ?ows in
the secondaries 34 and 36 are opposed and when ‘
these current flows are equal no signal is im
pressed on the ampli?er I3 and on the control‘
winding 38. The transformer secondaries 33 and 50
36 are connected in series 'in the input circuit
of the electronic ampli?er I3 by conductors 53,
54 and 55. Power is supplied to the ampli?er
I3 by means of conductors 56 and 51 leading from
the line wires 4| and 42. .The output circuit
from the electronic ampli?er I3 includes the con
trol winding 38 of the reversible electric motor
I4. The power winding 31 is connected across
the line wires 4| and 42 by conductors 53 and
the furnace I I decreases the current ?ow induced
in the secondary 36 decreases to rotate the re
versible electric motor I4 in the opposite direc
tion to move the carriage I6 to the left. Move
ment of the carriage I6 to the left makes the
potential of the grid 83 less negative to increase
the current flow induced in the secondary 36.
When the current ?ow in the secondary 36 be
comes equal to the current ?ow in the secondary
34 rotation of the reversible electric motor I4 is
stopped.
Accordingly the carriage I6 is posi
tioned in accordance with the temperature con
dition existing within the furnace II‘. It will be
recognized that a ?xed bias voltage may be
utilized in conjunction with the variable bias
obtained from battery I02 for controlling the
6| and a condenser 60 located in the conductor 60 potential of grid 83, if ‘desired.
From the above it is seen thatthe carriage I6
59, operates to cause the potential drop across
assumes positions corresponding to the tempera
the power winding 31 to lead the alternating ’
ture condition within the furnace II and records
potential of the line wires 4| and 42 by a suitable
these temperature conditions upon the chart
angle, for example 90°. When the current flows
20. By adjusting either or both of the rheostats
through the secondaries 34 and 36 are equal and
88 and I00, the system may be calibrated so
opposite, this being the case when the system is
that the correct temperature conditions are ex
balanced, no signal is impressed upon the elec
tronic ampli?er I3 and no potential drop is pro
hibited.
‘
As pointed out above the contacts 22 and 23
duced across the control winding 38 and the re
are positioned in accordance with the value of
versible electric motor I4 remains stationary.
the temperature condition it is desired to main
When the temperature condition Within the
tain within the furnace II. When the tempera
furnace II increases, the current flow in the
ture in the furnace II decreases below the pre
secondary 36 predominates over the current flow
determined value, contact 2| engages contact 22
in the secondary 34 to produce a signal for the
ampli?er 113 which is in phase with the line volt 75 to complete a circuit from the line wire 4| through
2,413,120
conductor 64, contacts 2I and 22, conductor 66,
reversible electric motor 24 and conductor 61 to
the line wire 42. This causes operation of the
reversible electric motor 24 to operate the valve
26 towards an open position to increasethe supply
of fuel to the furnace II. When the tempera
ture within the furnace increases above the de
Also during the ?rst half cycle current ?ow is
induced in the secondary 34 and ?ows down
wardly at that time and during the second half
cycle the induced current of the secondary 34
?ows upwardly. The ?ows of current in the sec
ondaries 34 and 36, therefore, oppose each other
sired value, contact 2I engages contact 23 to com
plete a circuit from the line wire 4| through
and when the current values are equal and op
posite no signals are impressed upon the elec
tronic ampli?er I3 and hence the reversible motor
conductor 64, contacts 2| and 23, conductor 65,
reversible motor 24 and conductor 61 to the line 10 I4 remains stationary. When the temperature
condition within the furnace II increases the gas
wire 42. This causes the reversible motor 24 to
operate in the opposite direction to move the - pressure in the electronic temperature respon~
sive device increases to increase the current flow
valve 25 towards a closed position to decrease the
through the secondary 36 to place a signal on
supply of fuel to the furnace II. In this manner
the temperature condition within the furnace II 15 the electronic ampli?er I3 which is in phase with
the line voltage. This causes the reversible motor
is maintained at any desired value.
1
I4 to operate in a direction to move the carriage
The arrangement illustrated in Fig. 2 is sub
I6 to the right. Upon a decrease in the tem
stantially the same as the arrangement illus
perature condition in thefurnace II the gas
trated in Fig. 1, but utilizes a different type of
electronic temperature responsive device. The 20 pressure in the electronic device H0 decreases to
decrease the current flow induced in the sec
electronic temperature responsive device in Fig. 2
ondary 36 whereupon a signal 180° out of phase
is generally designated at H6 and comprises a
with the line voltage is applied to the electronic
double envelope having enlarged portions III
ampli?er I3 for operating the reversible motor
and H3 and a connecting neck II 2. Located in
the enlarged portion III are a cathode H4, a 25 in the opposite direction to move the carriage
I6 to the left.
cathode heater H5, a control grid H6, and an
Here as in Fig. 1 the follow-up or rebalancing
anode H‘I. Radiation from the mass 36 in the
action is accomplished by controlling the grid of
furnace II passes through opening Si in the
the electronic device IIII, but the speci?c man
wall of the furnace II and is collected by a lens
system 32 and applied by a mirror H6 to the 30 ner in which the grid is controlled in Fig. 2 is
quite different from that of Fig. 1. The elec
enlarged portion H3 of the envelope. The en
tronic device H6 of Fig. 2 being a gas discharge
larged portion H3 contains a volatile ?uid or
device conducts during the ?rst half cycle when
gas and the vaporization of this volatile ?uid or
expansion of the gas depends'directly upon the ‘ the anode is positive. The grid H6 is controlled
by a phase shift bridge for determining the iri
stant during the ?rst half cycle at which the
hence upon the temperature condition within the
gas discharge device starts to conduct and, there
furnace H. Vaporization of the ?uid effects the
fore, determines the average current conducted
gas pressure within the envelope and the gas
by the gas discharge device. The phase shift
pressure inside of the envelope is directly de
pendent upon the temperature condition within 40 bridge includes in one arm between the cathode
H4 and the grid H6 the transformer secondary
the furnace H. Since cathode emission of the
I26, conductor I34, associated contact I33 and
gas type electronic device here illustrated is di
rectly dependent upon the gas pressure therein
resistance I32, and conductor I35. In the other
arm of the bridge between the cathode H4 and
the cathode emission depends directly upon the
temperature condition existing within the fur
the grid H6 are the transformer secondary I26,
nace H.
conductor I21 and an inductance I36. The in
The cathode heater I I5 is energized by a trans
ductance I36 and the variable resistance formed
former I20 having a primary I2I connected across
of resistance element I32 and contact I33 are so
line‘ wires 4I and 42 and a secondary I22 con
arranged that by adjusting the resistance I32
nected to the cathode heater H6. Alternating 50 the phase of the potential of the grid I I6 is varied
potentials are applied to the .output circuit and
with respect to the phase of the potential of the
the input or grid circuit of device H6 by means
line wires 4I and 42. By moving to the right the
of a transformer I23 having a primary I24 con
carriage I6 which carries the contact I33 the
nected across line wires 4I and 42 and second
resistance value of the resistance I32 is decreased
aries I26 and I26.
to retard the phase of the potential of the grid
During the ?rst half cycle of the alternating
H6 relatively to the phase of the potential of
potential it is assumed that the right end of the
the anode H1, whereupon the gas discharge de
secondaries I 25 and I26 is positive and at this
vice starts to conduct later during the ?rst half
time current ?ows through the output circuit
cycle, thus decreasing the average current con
extending from the secondary I26 through con
ducted by the discharge device@ By moving the
ductors I21 and I26, primary 35, conductor I29,
carriage I6 ‘to the left to increase the value of
anode II‘I, cathode H4 and conductor I36 to
resistance I 32 the phase of the potential of the
the transformer secondary I26. During the first
grid H6 with respect to the phase of the poten
half cycle current is, therefore, induced in the
tial of the anode II 1 is advanced whereby the
secondary 36 and flows upwardly in the direction
gas discharge device is allowed to conduct earlier
indicated by the arrow“ During the second half
during the ?rst half cycle.
cycle the electronic temperature responsive de
' amount of radiant energy affecting the same and
vice does not conduct but due to the construc
tion of the transformer means I2 current ?ows
downwardly through the secondary 36.
The
amount of current flow in the secondary 36
depends upon the gas pressure in the envelope
of the electronic temperature responsive device
and hence upon the temperature condition exist
ing within the furnace H.
When the temperature condition within the
furnace II increases, the current ?ow induced in
the secondary 36 increases to operate the re
versible electric motor I4 to move the carriage
I6 to the right. Movement of the carriage I6
to the right causes the gas dischargedevice to
conduct later in the cycle whereby the current
flow induced in the secondary 36 is decreased.
Wheprthe current flow in the secondary 36 is
2,413,120
decreased to a value corresponding to the current
?ow in the secondary 34 rotation of the reversible
electric motor I4 is stopped. Likewise upon a
decrease in the temperature condition within the
furnace I 1 current ?ow induced in the secondary
36 is decreased to cause the reversible electric
motor I4 to operate in the opposite direction to
move the carriage I6 to the left. Movement of
the carriage Hi to the left increases the value of
the resistance I32 to cause the gas discharge
device to conduct earlier during the ?rst half
cycle. This increases the current flow induced
in the secondary 36 and when the value of the
resistance in the secondary 36 becomes equal to
that induced in the secondary 34, the reversible
electric motor i4 is stopped. Accordingly the
carriage I6 is moved to a position corresponding
‘to the value of the temperature condition exist
ing within the furnace ll. Since the remainder
of the system is the same as the system outlined
above a further description of Fig. 2 is notcon
sidered necessary.
In the arrangements vof Figs. 1 and 2 described
above, the reversible electric motor I4 operates
a carriage I6 which operates to follow-up or
8
2. In a temperature responsive system, the
combination of, a source of alternating potential,
a multiphase reversible electric motor including
a power winding connected to the source of alter
nating potential and a control winding, trans
former means controlling the control winding
and including a pair of primaries, connections
between the primaries and the source of alter
nating potential to energize oppositely the trans
former means, electronic means, including an
anode, a grid and a cathode directly affected by
the temperature condition, included in said con
nections to vary relatively, the opposite energiza
tions of the transformer means to cause rotation
of the reversible electric motor in one direction
or the other, and means operated by the reversi
ble electric motor for controlling the bias on the
grid of the electronic means to vary relatively
the energizations of the transformer means to
equalize substantially the opposite energizations
to stop rotation of the reversible electric motor.
3. In a temperature responsive system, the
combination of, a source of alternating potential,
a, multiphase reversible electric motor including
a power winding connected to the source of alter
nating potential and a control winding, trans
rebalance the system, which exhibits and records
former means controlling the control winding
the value of the temperature condition existing
and including a pair’ of primaries, connections
within the furnace and which controls the supply
between the primaries and the source of alter
of fuel to the furnace to maintain a desired tem
nating potential to energize oppositely the trans
30
perature condition within the furnace. Of course
former means, electronic means, including an '
the fuel supply control means may be omitted,
anode, a grid and a cathode directly affected by
if desired, and if recording is not desired the
the temperature condition, included in said con-.
recording functions may be omitted. If record
nections to vary relatively the opposite energiza
ing and exhibiting is not desired it would be
desirable to utilize the reversible motor N for 35 tions of the transformer means to cause rotation
of the reversible electric motor in one direction
operating directly the fuel valve 25 in addition
or the other, and means operated by the reversi
to operating the follow-up or rebalancing means.
ble electric motor for controlling the phase of
This would provide a simple and accurate follow
the grid potential with respect to the phase of
up control system for maintaining desired con
the anode potential of the electronic means to '
40
ditions within the furnace ll.
vary relatively the energizations of the trans
While in accordance with the provisions of the
former means to equalize substantially the oppo
statutes, I have illustrated and, described the best
site energizations to stop rotation of the reversible
form of this invention now known to me, ‘it will
electric motor.
'
'
be apparent to those skilled in the art that
4. In a condition responsive system, the com
changes 'may be made in the form of the appa
bination of, an electrical device, an electronic dis
ratus disclosed without departing from the spirit
charge device including an anode, a cathode and
of this invention as set forth in the appended
a grid, an output circuit including the anode and
claims, and that in some cases certain features
cathode for controlling the electrical device,
of this invention may sometimes be used to ad
vantage without a corresponding use of other 50 means for controlling cathode emission in ac
cordance with the value of the condition, and
features.
means controlled by the electrical device for con
Having now described this invention, what I
claim, as new and desire to secure by Letters
Patent is:
1. In a, ‘temperature responsive system, the
trolling the grid.
5. In a temperature responsive system, the
combination of, an electrical device, an electronic
discharge device including an anode, a cathode
combination of , a source of alternating potential,
and avgrid, an output circuit including the anode
a multiphase reversible electric motor including
and cathode for controlling the electrical device,
a power winding connected to the source of alter
means for subjecting the cathode to the tempera
nating potential and a control winding, trans
ture condition for controlling cathode emission
former means controlling the control winding
in accordance with the value of the temperature
and including a pair ‘of primaries, connections
condition, and means controlled by the electrical
between theprimaries and the source of alter
device for controlling the grid.
nating potential to energize oppositely the trans
6. In a, condition responsive system, the com
former means, electronic means, including an
anode, a grid and a cathode directly affected by 65 bination of, an electrical device, a gas discharge
device including an anode, a cathode and a grid,
the temperature condition, included in said con
an output circuit including the anode and cathode
nections to vary relatively the opposite energiza
for controlling the electrical device, means for
tions of the transformermeans to cause rotation
varying the pressure in the gas discharge device
of the reversible electric motor in one direction
for controlling cathode emission in accordance
or the other, and means operated by the reversi
with the value of the condition, and means con
ble electric motor for controlling the grid of the
troliled by the electrical device for controlling the
electronic means to vary relatively the ‘energize.
gri .
tions of the transformer means to equalize sub
'7. In a, condition responsive system, the com
stantially the opposite energizations to stop rota
75 bination of, a source of alternating potential, an
tion of the reversible electric motor.
2,418,120
electronic discharge device including an anode, a
cathode and a grid, an output circuit including
the source of alternating potential, the anode and
cathode, means for controlling cathode emission
in accordance with the value of the condition, an
adjustable phase shifting bridge, and an input
circuit including the adjustable phase shifting
bridge, the-source of alternating potential, the
10
connected to a source of alternating potential, 9.
multiphase reversible electric motor including a
power winding connected to said terminals and
a control winding, transformer means controlling
the control winding and including a pair of
primaries, connections between the primaries and
said terminals to energize'oppositely the trans
former means, electronic means, including an
cathode and grid.
anode, a grid and a cathode directly affected by
8.‘ In a condition responsive system, the com
bination of, a source of alternating potential, a 10 the temperature condition, included in said con
nections to vary relatively the opposite energiza~
gas discharge device including an anode, a
tions of the transformer means to cause rotation
cathode and a grid, an output circuit including
of the reversible electric motor in one direction or
the source of alternating potential, the anode and
the other, and means operated by the reversible
cathode, means for varying the pressure in the
electric motor for controlling the bias on the grid
gas discharge device for controlling cathode emis
of the electronic means to vary relatively the en
sion in accordance with the value of the condi
ergizations of the transformer means to equalize
tion, an adjustable phase shifting bridge, and an
input circuit including the adjustable phase shift
ing bridge, the source of alternating ‘potential,
the cathode and grid.
9. In a temperature responsive system, the
combination of a pair of terminals adapted to
substantially the opposite energizations to stop
rotation of the reversible electric motor.
11. In a temperature responsive system, the
combination of a pair of terminals adapted to be
connected to a source of alternating potential, a
be connected to a source of alternating potential,
multiphase reversible electrical motor including
primaries, connections between the primaries and
said terminals to energize oppositely the trans
former means, electronic means, including an
anode, a grid and a cathode directly affected by
the temperature condition, included in said con
nections to vary relatively the opposite energiza
said terminals to energize oppositely the trans
former means, electronic means, including an
anode, a grid and a cathode directly affected by
the temperature condition, included in said con
nections to vary relatively the opposite energiza
a power winding connected to said teminals and
a multiphase reversible electric motor including
a power winding connected to said terminals and 25 a control winding, transformer means controlling
the control winding and including a pair of
a control winding, transformer means controlling
primaries, connections between the primaries and
the control winding and including a pair or
tions of the transformer means to cause rotation
of the reversible electric motor in one direction
or the other, and means operated by the re
versible electric motor for controlling the grid
of the electronic means to vary relatively the
energizations of the transformer means to
equalize substantially the opposite energizations
to stop rotation of the reversible electric motor.
10. In a temperature responsive system, the
combination of a pair of terminals adapted to be
tions of the transformer means to cause rotation
of the reversible electric motor in one direction
or the other, and means operated by the re—
versible electric motor for controlling the phase
of the grid potential with respect to the phase
of the anode potential of the electronic means to
vary relatively the energizations of the trans
former means to equalize substantially the op
posite energizations to stop rotation of the re
versible electric motor.
ARTHUR H. SWANSON.
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