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Патент USA US3094657

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June 18, 1963
3,094,647
K. s. FERRIN
CIRCUIT PROTECTION MEANS
Filed June 30, 1961
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United States Patent 0 ’ ice
1
3,094,647
CIRCUIT PROTECTION MEANS
Kenneth S. Ferrin, Sunnyvale, Calif., assiguor to General
3,094,647
Patented June 18, 1963
2
contacts in the second series circuit may be opened by
the energization of the relay coil in the ?rst series cir
cuit; similarly, the normally open contacts in another of
the protective circuits are closed by the energization of
Electric Company, a corporation of New York
the relay coil of the second series circuit. Thus, when
voltage is applied to the protective circuit, and the volt
age is within the desired voltage range, the second series
circuit provides a conductive path ‘between the electrical
This invention pertains to circuits for preventing dam
conductors, and the relay coil in the circuit is energized
age to other electrical circuits, and more particularly,
to thereby close the normally open contacts of another
to a protection means for preventing damage caused by 10 protective circuit. If the voltage drops below the zener
undervoltage or overvoltage conditions.
voltage of the zener diode in the second series circuit,
In electrical and electronic circuits it is frequently
the corresponding relay coil is deenergized, and the nor
necessary to require a plurality of power supplies or volt
mally opened contacts of another of the protective cir
age sources each ‘for providing a dilierent voltage to a
cuits are returned to their open position thereby discon
utilization circuit. These voltages may be used for re 15 necting the corresponding voltage supply from the utiliza~
lay operation, for bias supplies, as reference voltages,
tion circuit. Similarly, if the voltage between the con
and for many other uses throughout the electrical and
ductors exceeds the zener voltage of the zener diode in
electronic circuit. It is also usually necessary to insure
the ?rst series circuit, the relay coil in series therewith
that certain voltages are applied to the electrical or elec
opens the normally closed contacts in series with the sec
tronic circuit (utilization circuit) before the remainder 20 ond series circuit, and the relay coil in the second series
of the voltages are applied; similarly, in the event of a
circuit is thus de-energized, returning the normally open
failure or shut-down, it is also necessary that certain
contacts of another protective circuit to their open posi
voltages be removed from the utilization circuit before
tion.
the remainder of the supply voltages. Accordingly, the
The invention, both as to its organization and opera
prior art has provided complex sequencing mechanisms 25 tion together with further objects and advantages there
for applying various voltages in sequence, and has usual
of, may best be understood by reference to the follow
ly provided a complex system of delays to insure that
ing description taken in connection with the accompany—
certain voltages are not removed from the circuit before
ing drawing in which a schematic circuit is shown illus
other voltages.
trating an embodiment of the present invention.
In addition to the problem of sequencing the applica
Referring to the drawing, voltage sources 1, 2, 3, . . .
tion of power supply voltages to a utilization circuit,
N are shown for supplying respective voltages to a utiliza
overvoltage and undervoltage protection must be afforded
tion circuit 4. The power supplies are joined to the
to each of the power supplies individually; accordingly,
utilization circuit through protective circuits 10, 20, 30,
Filed June 30, 1961, Ser. No. 121,167
13 Claims. (Cl. 317-31)
the prior art has provided complex systems for sensing
. . . M, respectively. The protective circuit 10 is pro
and detecting the existence of overvoltage or undervolt 35 vided with a pair of normally open contacts 8', each hav
age conditions in the individual power supply, and for
ing one contact thereof connected to an output terminal
providing appropriate remedial action.
13 and 14, respectively, of the voltage source 1. The
Accordingly, it is an object of the present invention
other contacts of the pairs of contacts 8’ are connected
to provide an improved circuit for sequencing the appli
to
conductors 17 and 18, respectively. Conductors 17
40
cation of voltages to a utilization circuit.
and 18 are applied to the utilization circuit 4 to provide
It is also an object of the present invention to provide
the necessary voltage from the voltage source 1.
an overvoltage protection circuit.
Referring to protective circuit 10, two series circuits
It is a further object of the present invention to pro
25 and 26 are connected between electrical conductors
vide an undervolta-ge protection circuit.
17 and 18. The ?rst series circuit ‘25 includes a zener
It is still a further object of the present invention to
diode 31, a relay coil 32, and a resistor 33. The zener
provide a protection circuit for sequencing the application
of voltages to a utilization circuit while providing under
voltage and overvoltage protection to the utilization cir
cuit for each of the voltage sources.
Further objects and advantages of the present inven
tion become apparent as the description thereof pro
ceeds.
Brie?y, in accordance with one embodiment of the
present invention, a plurality of protection circuits are
provided, one for each voltage source and each con
nected to a utilization circuit, for sequencing the appli
cation of voltages to the utilization circuit. Each pro
tection circuit includes a pair of normally open contacts
in series therewith which are closed by the actuation of
a relay coil in another of the protection circuits.
A pair of electrical conductors are connected to the
normally open contacts, and are provided with two series
circuits joining the two conductors. The ?rst series cir
diode 31 is chosen to have a zener voltage equal to the
maximum permissible voltage to be supplied by the volt
age source 1. The second series circuit 26 includes a
zener diode 35, a relay coil 36, a resistor 37, and a pair
of normally closed contacts 38. The zener diode 35 is
chosen to have a zener voltage equal to the minimum
permissible voltage to be supplied by the voltage source
1. The normally closed contacts 38 are opened by the
energization of the relay coil 32 in the ?rst series circuit
25. The relay coil 36, when energized, operates the
normally open contacts in series with the electrical con
ductors of another protective circuit in a manner to be
explained more fully hereinafter.
'
‘Protectice circuits 20, 30, . . . M ‘are identical with
the protective circuit 10. Thus, the pairs of normally
open contacts 36’ of protective circuit 20‘ are closed by
the energiza-tion of the relay coil 36 of the protective
circuit 10. Similarly, the pairs of norm-ally open con
cuit contains a zener diode and a relay coil in series; the 65 tacts 362’ of protective circuit 30 are closed by the en
ergization of the relay coil 362 of protective circuit 20.
zener diode has a zener voltage equal to the maximum
The pair of normally closed contacts 38 in the second
permissible voltage of the respective voltage supply.
series circuit 26 of each protective circuit is openable
The second series circuit contains a zener diode, a relay
upon energization of the relay coil 32 of the ?rst series
coil, and a pair of normally closed contacts. The zener
voltage of the zener diode in the second series circuit 70 circuit 25 of the respective circuit. Thus, energization
of the relay coil 32 in protective circuit 10 will open the
is chosen to be equal to the minimum voltage permissible
normally closed contacts 38 of protective circuit 10; en
for the respective power supply. The normally closed
3,094,647
3
4
.
ergization of the relay coil 322 of protective circuit 20
succeeding voltage source ‘to the utilization circuit. If
will open the normally closed contacts 382 of protective
circuit 28; etc.
the voltages from any of the voltage sources exceeds the
maximum permissible voltage, or fails to maintain a volt
To provide a means for initiating the
application of the voltages from the voltage sources 1,
age above the minimum permissible voltage, all succeed
ing voltage sources would be disconnected from the utili
zation circuit. For example, if the circuit shown in the
' 2,3, . . . N to the utilization circuit 4, the manual switch
5, connected to a suitable potential source (not shown)
through terminals 6 and 7, may be provided to ener
drawing is operating properly, and the voltage from the
gize a relay coil 8. The relay coil 8, when energized,
voltage source 2 should suddenly exceed the maximum
closes normally opened contacts 8' of the protective cir
permissible voltage level for that source, the zener diode
cuit 10, and thus initiates a sequencing action for the 10 312 of protective circuit 20 would permit the energization
application of the voltages from the voltage sources to
of the corresponding relay coil 322, and thus would cause
the utilization circuit 4.
the opening of the normally closed contacts 382 of the
protective circuit 20. With normally closed contacts 382
open, all succeeding voltage sources would become dis
by the voltage source 1 is to be ‘applied to the utiliza 15 connected from the utilization circuit 4.
tion circuit 4, ?rst, the voltage supplied by the voltage
It may ‘be convenient to connect a suitable indicating
source 2, second, and the voltage supplied by the voltage
means such as, for example an indicator lamp (not
source 3, third, etc, the circuit of the present invention
shown), across the conductors of the protective circuit;
provides the proper sequenching by closing the manual
in this manner, the condition of each protective circuit
switch 5 thus energizing the relay coil 8. The energiza 20 may
be observed, and those protective circuits which have
tion of relay coil 8 closes normally open contacts 8’ of
been disconnected from the respective voltage source by
the protective circuit 10, thereby applying the voltage
The operation of the embodiment shown in the draw~
ing is as follows. Assuming that the voltage supplied
a preceding protective circuit may be determined by the
condition of the indicating means. The resistors 33 and
37 of each protective circuit serve a current limiting
function, and may be removed if the duty cycle of circuit
protective means is short. One of the pair of normally
from voltage source 1 to the utilization circuit 4. If the
voltage thus applied is under the minimum permissive
voltage for the utilization circuit 4, zener diode 35 will
prevent conduction in the second series circuit 26; thus,
relay coil 36 will not become energized, and the nor
mally open contacts 36', 362’ of protective circuits 20,
open contacts 8', 36', 362', and conductors 18, 182, 183,
39, . . . M will remain open, and the voltages from
voltage sources 2, 3, . . . N will not be applied to the 30
utilization circuit 4. ‘If the voltage applied by the voltage
source 1 exceeds the maximum permissive voltage, zener
diode 31 will permit conduction through the ?rst series
circuit 25, and thus will permit energization of the relay
coil 32. The relay coil 32, when energized, opens the
normally closed contacts 38 of the second series circuit
26. When the second series circuit is opened-circuited,
relay coil 36 is de-energized, and the normally open con~
tacts 36', 362', of protective circuits 20, 30, . . . M re
may be eliminated in those instances Where one side of
the voltage is grounded, the series circuits then being
grounded at the low voltage side thereof.
While the principles of the invention have now been
made clear in illustrative embodiments, there will vbe im
mediately obvious to those skilled in the art many modi
?cations in structure, arrangement, proportions, the ele
ments, materials, and components, used in the practice
of the invention, and otherwise, which are particularly
adapted for speci?c environments and operating require
ments, Without departing from those principles. The ap~
pended claims are therefore intended to cover and em
main in, or are returned to, their normally open states. 40
brace any such modi?cations, within the limits only of
If the voltage applied by the voltage source 1 is above
the minimum, and below the maximum permissive volt
age, zener diode 35 will permit conduction in the series
the true spirit and scope of the invention.
What is claimed as new and desired to secure by let
ters patent of the United States is:
1. Circuit protection means including a plurality of
in the ?rst series circuit 25; accordingly, the normally 45 protective circuits each comprising, a pair of input ter
open contacts 36' of the protective circuit 20 will be
minals, a ?rst and a second pair of normally open contacts
- closed, and the voltage from the second voltage source
each pair having one contact thereof connected to one of
2 will be applied to the utilization circuit 4.
said input terminals, a pair of electric conductors each
‘If the voltage from the second voltage source is under
connected to the other contact of one of said pairs of
the permissive voltage for that source, zener diode 352 50 normally open contacts, respectively, a ?rst series circuit
of protective circuit 20 will prevent energization of relay
connected between said conductors including a zener diode
. coil 362 of protective circuit 20, and will thus inhibit the
and a relay coil, said zener diodes having a zener voltage
circuit 26, and zener diode 31 will prevent conduction
closing of normally open contacts 362’ of protective cir
cuit 30. Similarly, if the applied voltage from voltage
equal to a predetermined maximum voltage, a second series
circuit connected between said conductors including a
source 2 exceeds the maximum permissible voltage, zener 55 zener diode, a relay coil, and a pair of normally closed
diode 312 of protective circuit 20 will permit energization
contacts, said zener diode of said second series circuit hav
of the relay coil 322 and thus will cause the opening of
ing a zener voltage equal to a predetermined minimum
the normally closed contacts 382 of protective circuit 20.
voltage, said normally closed contacts adapted to open
When the normally closed contacts 382 of protective
when said relay coil of said ?rst series circuit is energized,
circuit 20 are opened, relay 362 of protective cir 60 said ?rst ‘and second pairs of normally open contacts
cuit 20 is de-energized, and the normally open contacts
adapted to close when the relay coil of the second series
362’ of protective circuit 30 remain open, thus prevent
circuit of another of said protective circuits is energized,
ing the application of the voltage from voltage source 3
said circuit protection means also including energizable
to the utilization circuit 4. If the voltage from the volt
means ‘for closing the normally open contacts of one of
age source 2 is of the proper or permissive value, nor 65 said plurality of protective circuits.
mally open contacts 362' of the protection circuit 30‘
2. Circuit protection means including a plurality of pro
will be closed, and protection circuit 30 will then provide
tective circuits each comprising, a pair of input terminals,
a ?rst and a second pair of normally open contacts each
a similar overvoltage and undervoltage protection to the
pair having one contact thereof connected to one of said
utilization circuit 4 for the voltage supplied ‘by the volt
70 input terminals, a pair of electrical conductors each con
age source 3.
nected to the other contact of one of said pairs of normal
If all of the voltages from the voltage sources 1, 2, 3,
ly open contacts, respectively, a series circuit connected
. . . N are successively applied to the utilization circuit
between said conductors including a zener diode and a
4, each protective circuit will continue to permit the suc
relay
coil, said zener diode having a zener voltage equal
ceeding protective circuit to supply the voltage from the
to a predetermined maximum voltage, means connected
3,094,647
5
between said conductors responsive to voltages above a
predetermined minimum voltage between said conductors
‘for closing said ?rst and second pairs of normally open
energizable means for closing the normally open contacts
of one of said plurality of protective circuits.
6. In combination, a utilization circuit, a plurality of
Voltage sources each adapted to supply a given voltage to
said utilization circuit, a plurality of protective circuits
contacts of another of said protective circuits, said means
also responsive to the energization of said relay coil for
each connecting a different one of said voltage sources
disabling said means to prevent the closing of said ?rst
to said utilization circuit, each of said protective circuits
and second pairs of normally open contacts of another of
comprising, ?rst and second input terminals, means con
said protective circuits, said circuit protection means also
necting said input terminals to one of said voltage sources,
including energizable means for closing the normally open
contacts of one of said plurality of protective circuits. 10 ?rst and second pairs of normally open contacts each
pair having one contact thereof connected to one of said
3. Circuit protection means including a plurality of pro
input terminals, a pair of electrical conductors each con
tective circuits each comprising, a pair ‘of input terminals,
nected to the other contact of one of said pairs of normally
21 ?rst and a second pair of normally open contacts each
open contacts, respectively, a series circuit connected be
pair having one contact thereof connected to one of said
input terminals, a pair of electrical conductors each con 15 tween said conductors including a zener diode and a
relay coil, said zener diode having a zener voltage equal to
nected to the other contact of one of said pairs of nor
a predetermined maximum voltage, means connected be
mally open contacts, respectively, ?rst means connected
tween said conductors responsive to voltages above a pre
between said conductors responsive to voltages above a
determined minimum voltage between said conductors for
predetermined minimum voltage between said conductors
for closing said ?rst and second pairs of normally open 20 closing said ?rst and second pairs of normally open con
tacts ‘from another of said protective circuits, said means
contacts of another of said protective circuits, and second
also responsive to the energization of said relay coil for
means connected between said conductors responsive to
disabling said means to prevent the closing of said ?rst
voltages above a predetermined maximum voltage be
and second pairs of normally open contacts of another
tween said conductors for disabling said ?rst means to
prevent the closing of said ?rst and second pairs of nor 25 of said protective circuits, and energizable means for clos
ing the normally open contacts of one of said plurality
mally open contacts of another of said protective circuits,
of protective circuits.
said circuit protection means also including energizable
7. In combination, a utilization circuit, ‘a plurality of
voltage sources each adapted to supply a given voltage to
4. Circuit protection means including a plurality of pro 30 said utilization circuit, a plurality of protective circuits
means for closing the normally open contacts of one of
said plurality of protective circuits.
tective circuits each comprising, a pair or input terminals,
?rst and second pairs ‘of normally open contacts each pair
having one contact thereof connected to one of said input
each connecting a different one of said voltage sources to
said utilization circuit, each of said protective circuits
comprising, a ?rst and a second input terminal, means
connecting said input terminals to one of said voltage
terminals, a pair of electrical conductors each connected
to the other contact of one of said pairs ‘of normally open 35 sources, ?rst and second pairs of normally open contacts
each pair having one contact thereof connected to one of
contacts, respectively, a series circuit connected between
said input terminals, a pair of electrical conductors each
said conductors including a zener diode and a relay coil,
connected to the other contact of one of said pairs of
said zener diode having a zener voltage equal to a pre
normally open contacts, respectively, ?rst means con
determined maximum voltage and poled to inhibit current
nected between said conductors responsive to voltages
?ow in said series circuit when the voltage between said
above a predetermined minimum voltage between said
conductors is less than said maximum voltage, and means
conductors for closing said ?rst and second pairs of nor
connected between said conductors responsive to volt-ages
mally open contacts of another of said protective circuits,
above a predetermined mini-mum voltage between said
second means connected between said conductors respon
conductors for closing said ?rst and second pairs of nor
mally ‘open contacts of another of said protective circuits, 45 sive to voltages above a predetermined maximum volt
age between said conductors for disabling said ?rst means
said means also responsive to the energization of said
to prevent the closing of said ?rst and second pairs of
relay coil for disabling said means to prevent the closing
normally open contacts of another of said protective cir
of said ?rst and second pairs of normally open contacts
cuits, and energizable means for closing the normally
of another of said protective circuits, said circuit protec
open contacts of one of said plurality of protective
tion means also including energizable means for closing
the normally open contacts of one of said plurality of
circuits.
8. In combination, a utilization circuit, a plurality of
protective circuits.
voltage sources each adapted to supply a given voltage to
5. In combination, a utilization circuit, a plurality of
said utilization circuit, a plurality of protective circuits
voltage sources each adapted to supply a given voltage to
each connecting a different one of said voltage sources to
said utilization circuit, a plurality of protective circuits
each connecting a different one of said voltage sources to 55 said utilization circuit, reach of said protective circuits com
said utilization circuit, each of said protective circuits
prising, a ?rst and a second input terminal, means con~
comprising, ?rst and second input terminals, means con
necting said input terminals to one of said voltage sources,
?rst and second pairs of normally open contacts each pair
meeting said input terminals to one of said voltage sources,
having one contact thereof connected to one of said input
having one contact thereof connected to one of said input 60 terminals, a pair of electrical conductors each connected
to the other contact of one of said pairs of normally open
terminals, a pair of electrical conductors each connected
to the other contact of one of said pairs of norm-ally open
contacts, respectively, a series circuit,cQnnected~between’M"
?rst and second pairs of normally open contacts each pair
contacts, respectively, a ?rst series circuit connected be
said conductors including a'z'ener diode ‘and a relay coil,
tween said conductors including a zener diode and a relay
said zener diode having a zener voltage equal to a pre
coil, said zener diode having aeezener voltage equal to a 65 determined maximum voltage and poled to inhibit current
flow in said series circuit when the voltage between said
connected between said conductors including a zener
conductors is less than said maximum voltage, means con
diode, a relay coil, and a pair of normally closed con
nected between said conductors responsive to voltages
tacts, said zener diode of said second series circuit having
above a predetermined minimum voltage between said
a zener voltage equal to a predetermined minimum volt 70 conductors for closing said ?rst ‘and second pairs of nor
age, said normally closed contacts adapted to open when
mally open contacts of another of said protective circuits,
said relay coil of said ?rst series circuit is energized, said
said means also responsive to the energization of said
‘predetermined maximum voltage, a second series circuit
?rst and second pairs of normally open contacts adapted
relay coil for disabling said means to prevent the closing
of another of said protective circuits is energized, and 75 of said ?rst and second pairs of normally open contacts
to close when the relay coil ‘of the second series circuit
_
3,094,647
7
of another of said protective circuits, and energizable
means for closing the normally open contacts of one of
said plurality of protective circuits.
9. In combination, a utilization circuit, a plurality of
voltage sources each adapted to supply a ‘given voltage to
said utilization circuit, a plurality of protective circuits
each connecting a di?erent one of said voltage sources to
8
clnding a zener diode and a relay coil, said zener diode
having a zener voltage equal to a predetermined maximum
voltage, a second series circuit connected between said
conductors including a zener diode, a relay coil, and a pair
of normaly closed contacts, said zener diode of said sec~
0nd series circuit having a zener voltage equal to a pre
determined minimum voltage, said normally closed con
tacts adapted to open when said relay coil of said ?rst
series circuit is energized, said normally opened contacts
open contacts having one contact thereof connected to one 10 adapted to close when the relay coil of the second series
of said input terminals, a ?rst electrical conductor con
circuit of another of said protective circuits is energized,
nected to the other of said input terminals, a second elec
said circuit protection means also including energizable
said utilization circuit, each of said protective circuits
comprising, a pair of input terminals, a pair of normally
trical conductor connected to the other contact of said
means for closing the normally open contacts of one of
pair of normally open contacts, a ?rst series circuit con
said plurality of protective circuits.
nected between said conductors including a zener diode 15
12. Circuit protection means including a plurality of
and a relay coil, said zener diode having a zener voltage
protective circuits each comprising, a pair of input termi—
equal to a predetermined maximum voltage, a second
nals, a pair of normally open contacts having one con
series circuit connected between said conductors including
tact thereof connected to one of said input terminals, a
a zener diode, a relay coil, and a pair of normally closed
?rst electrical conductor connected to the other of said
contacts, said zener diode of said second series circuit
input terminals, a second electrical conductor connected
having a zener voltage equal to a predetermined minimum
to the other contact of said pair of normally open con
voltage, said normally closed contacts adapted to open
tacts, ?rst means connected between said conductors re
when said relay coil of said ?rst series circuit is energized,
said pair of normally open contacts adapted to close when
sponsive to voltages above a predetermined minimum
voltage between said conductors ‘for closing said pair of
the relay coil of the second series circuit of another of
said protective circuits is energized, and energizable means
for closing the normally open contacts of one of said
normally open contacts of another of said protective cir
cuits, second means connected between said conductors
plurality of protective circuits.
tween said conductors for disabling said ?rst means to
10. In combination, a utilization circuit, a plurality of
voltage sources each adapted to supply a given voltage
to said utilization circuit, a plurality of protective circuits
each connecting a different one of said voltage sources to
said utilization circuit, each of said protective circuits
comprising, a pair of input terminals, a pair of normally
open contacts having one contact thereof connected to
one of said input terminals, a ?rst electrical conductor
connected to the other of said input terminals, a second
electrical conductor connected to the other contact of
said pair of normally open contacts, ?rst [means connect
ed between said conductors responsive to voltages above a
predetermined minimum voltage between said conductors
for closing said pair of normally open contacts of another
of said protective circuits, second means connected be
tween said conductors responsive to voltages above a
predetermined maximum voltage between said conductors
responsive to voltages above a predetermined voltage be
prevent the closing of said pair of normally open con
tacts of another of said protective circuits, said circuit
protection means also including energizable means for
closing the normally open contacts of one of said plurality
of protective circuits.
13. Circuit protection means including a plurality of
protective circuits each comprising, a pair of input termi
nals, a pair of normally open contacts having one contact
thereof connected to one of said input terminals, a pair
of electric conductors, one of said conductors connected
to the other contact of said pair of normally open contacts,
the other of said conductors connected to the other of said
pair of input terminals, a ?rst series circuit connected be
tween said conductors including a zener diode and a relay
coil, said zener diodes having a zener voltage equal to a
predetermined maximum voltage, a second series circuit
connected between said conductors including a zener
for disabling said ?rst means to prevent the closing of said
diode, a relay coil, and a pair of normally closed con
pair of normally open contacts of another of said protec
tacts, said zener :diode of said second series circuit having
tive circuits, and energizable means for closing the nor
a zener voltage equal to a predetermined minimum volt
mally open contacts of one of said plurality of protective
age, said normally closed contacts adapted to open when
circuits.
50 said relay coil of said ?rst series circuit is energized, said
11. Circuit protection means including a plurality of
normally open contacts adapted to close when the relay
protective circuits each comprising, a pair of input termi
coil of the second series circuit of another of said pro
nals, a pair of norm-ally open contacts having one con
tective circuits is energized, said circuit protection means
tact thereof connected to one of said input terminals, a
also including energizable means for closing the normally
?rst electrical conductor connected to the other of said 55 open contacts of one of said plurality of protective cir
input terminals, a second electrical conductor connected
cuits.
to the other contact of said pair of normally open contacts,
a ?rst series circuit connected between said conductors in
No references cited.
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