CA1086420A - Networks for limiting x-radiation from cathode ray tubes - Google Patents
Networks for limiting x-radiation from cathode ray tubesInfo
- Publication number
- CA1086420A CA1086420A CA278,305A CA278305A CA1086420A CA 1086420 A CA1086420 A CA 1086420A CA 278305 A CA278305 A CA 278305A CA 1086420 A CA1086420 A CA 1086420A
- Authority
- CA
- Canada
- Prior art keywords
- cathode ray
- eht
- ray tube
- sensing device
- beam current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/021—Details concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order
- H02H3/023—Details concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order by short-circuiting
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/38—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to both voltage and current; responsive to phase angle between voltage and current
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/63—Generation or supply of power specially adapted for television receivers
Landscapes
- Engineering & Computer Science (AREA)
- Multimedia (AREA)
- Signal Processing (AREA)
- Direct Current Feeding And Distribution (AREA)
Abstract
ABSTRACT
Operation of a cathode ray tube above the Isodose line is prevented by generating voltages that are propor-tional to both the EHT supplied to the cathode ray tube and the beam current of the cathode ray tube. These voltages are applied to a sensing device, such as a neon tube, which generates a trigger pulse when the voltage across it exceeds some predetermined magnitude. The sensing device is selected so that the trigger pulse is generated always below the Isodose line. The trigger pulse is used to inhibit operation of the cathode ray tube as by interrupting the supply of EHT to the cathode ray tube.
Operation of a cathode ray tube above the Isodose line is prevented by generating voltages that are propor-tional to both the EHT supplied to the cathode ray tube and the beam current of the cathode ray tube. These voltages are applied to a sensing device, such as a neon tube, which generates a trigger pulse when the voltage across it exceeds some predetermined magnitude. The sensing device is selected so that the trigger pulse is generated always below the Isodose line. The trigger pulse is used to inhibit operation of the cathode ray tube as by interrupting the supply of EHT to the cathode ray tube.
Description
~ 0 ~ ZO
Background of the Invention This invention relates to networks for use in association with devices that are capable o~ emitting,but, in norm~l operation, are not intended to emit, x-rays, for inhibiting operation of the devices in regions where they emit x-rays over and above some predetermined limit. More specifically, this invention relates to networks for auto-matically reducing or eliminating the high voltage (EHT) which is applied to the cathode ray tube (CRT) of a television receiver, monitor or the like before the CRT
reaches a mode of operation where it would emit x-rays over and above some predetermined limit.
So called "crowbar circuits" are used to turn off the high voltage circuits of television receivers and monitors in the event that the high voltages generated by these circuits become excessive to the point where the cathode ray tubes of the receivers or monitors might generate x-rays over and above some predetermined limit.
Thus, in the past the EHT, or a fixed fraction of the EHT, has been sensed and used to trigger the crowbar circuit, the triggering taking place at a specific, predetermined .. . .
EHT magnitude regardless of the beam current of the CRT.
However, it is known that the x-ray limit of a CRT
does not follow a constant voltage vs. beam current charac-teristic, but more closely approximates a constant power curve. Consequently, it would be desirable for the characteristic of the crowbar circuit also to approximate a constant power curve, albeit a lower constant power curve than the x-ray limit of the CRT in question. This can be achieved by making the crowbar characteristic follow the actual high voltage supply characteristic in order to keep below the x-ray limit of the CRT.
~.
6~2~
., Summary of the Invention In accordance with one aspect of this invention there is provided in combination with a cathode ray tube ; having means for supplying EHT thereto and an EHT vs. beam current characteristic defining on one side of said character-istic an undesired mode of operation and on the other side of said characteristic a desired mode of operation, means for inhibiting operation of said cathode ray tube on said one side of said characteristicj said inhibiting means compris-ing means for deriving voltages proportional to both the EHT
supplied to said cathode ray tube and the beam current of ~ said cathode ray tube, means for supplying said voltages to ; a sensing device, said sensing device being adapted to . produce a trigger pulse when the voltage across said sensing device exceeds a predetermined magnitude, said sensing device being selected such that said trigger pulses always occur at an EHT and beam current value that is on said other side of said characteristic and means responsive to the generation of said trigger pulse for inhibiting the operation of said cathode ray tube, by interrupting the supply of EHT from said supplying means to said cathode ray tube.
:~ Brief Description of the Drawin~s This invention will become more apparent from the ~` following detailed description, taken in conjunction with the appended drawings, in which:
Figure 1 is a block diagram of a television receiver employing a tracking V-I crowbar circuit embody-ing this invention;
Figure 2 are curves plotted on a Y axis of EHT
and an X axis of beam current useful in explaining this invention; and -la-,æ
64~
Figure 3 is a schematic of a part of the television receiver shown in Figure 1.
Detailed Description of the Invention Including the Preferred Embodiment " _ Referring to Figure 2, curve 10 designates the x-ray limit of a given CRT. Curve 10 also is referred to as the Isodose line or the 0.5 m R/hr. Isoexposure - Rate Limit Curve. There is one isodose line for all CRTs of one type, and it represents the worst case of any CRT of that particular type. The area above curve 10 is a forbidden zone, i.e., operation of the CRT within that zone i i .
~c ~
~6~
may pro~uce x-rays above a predetermined limit, name~y that prescribed by curve 10. Dotte~ curve 11 designates the crowbar trip characteristic of a prior art crowbar network that responds solely to EHT. At the point where curves 10 and 11 intersect, the beam current of the CRT
is Ic. It can be seen from Fig. 2 that as long as the beam current is below Ic, the crowbar circuit will preclude operation in the forbidden zone. However, with beam currents greater than Ic, operation within the forbidden zone in the shaded area designated 12 is possible indicating that a crowbar network which responds solely to EHT is not satisfactory.
Still referring to Figure 2, curve 13 designates the V-I characteristic of a typical EHT power supply. In order to prevent nuisance triggering under various noise and transient conditions, at zero beam current curve ll-is preset to be at some predetermined level higher than curve 13. For example, a 6% differential between curves 11 and ! ... .
13 at ~ero beam current may be used. This 6% differential is not maintained at other beam currents, however, as may be seen by the divergence of curves 11 and 13.
;~ Curve 14 in Figure 2 designates the crowbar trip characteristic of a crowbar network embodying this invention '~ that is responsive not only to EHT, but also to beam current.
Like curve 11, it intersects the Y axis at a voltage 6%
above that at the intersection of curve 13 with the Y axis. `
However, unlike curve 11, curve 14 remains below curve 10 and between curves 10 and 13 regardless of beam current, . . ..
.` .
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., .
: :
,: . ' ' . ~
so operation of the CRT within the forbidden zone is positively prevented.
Referring to Figure l, a low voltage regulator 16 which provides a D.C. output of, say, twenty-four volts, supplies the horizontal driver system 17 and other conven-tional components 18 of a television receiver, these com-ponents 18 being the tuner, I.F., video, audio, chroma, etc.
ne~works of the receiver. A.C. power is supplied to regulator 16 via a power transformer l9. Horizontal driver 10 system 17 includes an output transformer 21 having a flyback tertiary winding 20 that is connected to a voltage tripler 22 and a crowbar circuit 23. One output terminal of voltage tripler 22 is connected to the EHT button of a CRT. Tripler 22 also has an output terminal that is connected to crowbar circuit 23 so that a part of the EHT output of tripler 22 can be supplied to the crowbar circuit. The output of crow-, bar circuit 23 is supplied to low voltage regulator 16 and controls the output voltage thereof and hence the output voltage of horizontal driver systern 17.
Referring to Figure 3, crowbar circuit 23 includes a resistor Rl~ a resistor R2, a light emitting diode LEDl, a ~: capacitor C1 and a silicon controlled rectifier SCRl con-; nected as shown in the Figure. Voltage tripler 22 includes diodes Dl-D5, a resistor R3 and capacitors C2-C6 connected as shown in the Figure.
ReiEerring to Fig. l, a voltage which is directly proportional to the EHT developed at output terminals 25 of tripler 22 is developed at the other output terminal 24 of tripler 22 and is applied, referring now to Fig. 3, across 30 a voltage divider that includes the following serially con-nected components resistors R4 and R5, potentiometer Pl and resistor R6. The slider 26 of potentiometer Pl is connected to one electrode of a neon lamp 27.
i42~
The beam current of the CRT is drawn through a resistor R7 that is shunted by a capacitor C7. Consequently a voltage is developed across resistor R7 that is directly proportional to the beam current of the CRT, and this voltage is applied to the other electrode of neon lamp 27 via a resistor R8. Thus, from potentiometer Pl there is applied to one electrode of neon lamp 27 a voltage VA that is directly proportional to E~T and increases positively as EHT increases, while there is applied to the other electrode of neon lamp 27 a voltage VB that increases negatively with increasing beam current. The voltage VN across lamp 27 is equal to VA - VB, and when VN exceeds the trigger voltage of neon lamp 27, as a result of either an increase in EHT
or an increase in beam current or an increase in both, neon lamp 27 fires producing a pulse which is applied via a resistor R9 and a capacitor C8 to the gate electrode of silicon controlled rectifier SCRl turning on the silicon controlled rectifier. The turning on of the silicon con-trolled rectifier is signalled by illumination of light emitting diode LEDl and short ci:rcuits a portion of low voltage regulator 16 (Figure 1), thereby completely turning off the EHT. ~ecause the silicon controlled rectifier remains on after triggering, EHT remains off until the power has been removed, the originating fault rectified and power reapplied.
The time constant of resistor R7 and capacitor C7 is chosen to be substantially equal to that of the network supplying VA in order to maintain tracking and prevent false triggering during initial power application and during high ; 30 voltage arcing.
While in the embodiment shown a voltage VB that increases negatively witll increasing beam current is applied :.
.
to the righ~ hand electrode of neon lamp 27, alternatively it would be possible to apply to the left hand electrode of neon lamp 27 a voltage along with VA that increases positively with increasing beam current.
It is not essential to the invention that a neon lamp 27 be employed. Thus a diac, a Zener diode and asso-cia~ed circuitry or any other device or network that breaks down when a predetermined voltage is applied across it and then produces a trigger pulse could be used.
It also is not essential that a silicon controlled rectifier be used. The SCR could be replaced by its two 0 transistor equivalent circuit or by a flip-flop network.
It should be noted that the degree of V-I tracking, i.e., the slope of curve 14, can be controlled by varying the magnitude of resistor R7. Thus, if R7 = O, only EHT
will be tracked and curve 14 reverts to curve 11. Resistor R7 may be made variable, if desired, to permit the slope ,~ of curve 14 to be varied.
As an additional and preferred feature, but not essential to the invention in its broader aspects, there is provided an overcurrent detecting circuit 28 which is designed to protect the CRT in the event of a large beam overcurrent occurring. This circuit is constituted by resistor R10;, capacitor C9, zener diode Zl, transistor TRl and its associated resistors Rll - R13. The beam current at which circuit 28 activates is determined by the value of resistor R7 and the trigger voltage of zener diode Zl. When the beam current is sufficiently large to produce a voltage : across resistor R7 that is greater than the zener voltage of zener diode Zl, the latter will fire turning off transistor ; -6-~ 6~
TRl and triggering silicon controlled rectifier SCRl so as to cause the EHT to drop to zero.
It should be noted that the entire crowbar circuit 23 could be replaced with MOTOROLA (trade mark) IC MC3423 or MC3523, particularly where VA and VB are applied to the same sensing input.
It also should be noted that the desired result can be achieved other than by turning off the EHT for the CRT. Thus, operation of the crowbar circuit could be arranged to turn off the beam current of the CRT at the ~ cathode thereof, to bias Gl of the CRT negative, thereby ; interrupting beam current, to cause the frequency of the high frequency oscillator to go out of sync and increase in frequency, causing EHT to decrease. In addition, flow of current through the SCR could be arranged to blow a power supply fuse.
While a preferred embodiment of the invention has been disclosed, those skilled in the art will appreciate that changes may be made therein without departing from the spirit and scope of this invention as defined in the - appended claims.
.
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.- ~ .
Background of the Invention This invention relates to networks for use in association with devices that are capable o~ emitting,but, in norm~l operation, are not intended to emit, x-rays, for inhibiting operation of the devices in regions where they emit x-rays over and above some predetermined limit. More specifically, this invention relates to networks for auto-matically reducing or eliminating the high voltage (EHT) which is applied to the cathode ray tube (CRT) of a television receiver, monitor or the like before the CRT
reaches a mode of operation where it would emit x-rays over and above some predetermined limit.
So called "crowbar circuits" are used to turn off the high voltage circuits of television receivers and monitors in the event that the high voltages generated by these circuits become excessive to the point where the cathode ray tubes of the receivers or monitors might generate x-rays over and above some predetermined limit.
Thus, in the past the EHT, or a fixed fraction of the EHT, has been sensed and used to trigger the crowbar circuit, the triggering taking place at a specific, predetermined .. . .
EHT magnitude regardless of the beam current of the CRT.
However, it is known that the x-ray limit of a CRT
does not follow a constant voltage vs. beam current charac-teristic, but more closely approximates a constant power curve. Consequently, it would be desirable for the characteristic of the crowbar circuit also to approximate a constant power curve, albeit a lower constant power curve than the x-ray limit of the CRT in question. This can be achieved by making the crowbar characteristic follow the actual high voltage supply characteristic in order to keep below the x-ray limit of the CRT.
~.
6~2~
., Summary of the Invention In accordance with one aspect of this invention there is provided in combination with a cathode ray tube ; having means for supplying EHT thereto and an EHT vs. beam current characteristic defining on one side of said character-istic an undesired mode of operation and on the other side of said characteristic a desired mode of operation, means for inhibiting operation of said cathode ray tube on said one side of said characteristicj said inhibiting means compris-ing means for deriving voltages proportional to both the EHT
supplied to said cathode ray tube and the beam current of ~ said cathode ray tube, means for supplying said voltages to ; a sensing device, said sensing device being adapted to . produce a trigger pulse when the voltage across said sensing device exceeds a predetermined magnitude, said sensing device being selected such that said trigger pulses always occur at an EHT and beam current value that is on said other side of said characteristic and means responsive to the generation of said trigger pulse for inhibiting the operation of said cathode ray tube, by interrupting the supply of EHT from said supplying means to said cathode ray tube.
:~ Brief Description of the Drawin~s This invention will become more apparent from the ~` following detailed description, taken in conjunction with the appended drawings, in which:
Figure 1 is a block diagram of a television receiver employing a tracking V-I crowbar circuit embody-ing this invention;
Figure 2 are curves plotted on a Y axis of EHT
and an X axis of beam current useful in explaining this invention; and -la-,æ
64~
Figure 3 is a schematic of a part of the television receiver shown in Figure 1.
Detailed Description of the Invention Including the Preferred Embodiment " _ Referring to Figure 2, curve 10 designates the x-ray limit of a given CRT. Curve 10 also is referred to as the Isodose line or the 0.5 m R/hr. Isoexposure - Rate Limit Curve. There is one isodose line for all CRTs of one type, and it represents the worst case of any CRT of that particular type. The area above curve 10 is a forbidden zone, i.e., operation of the CRT within that zone i i .
~c ~
~6~
may pro~uce x-rays above a predetermined limit, name~y that prescribed by curve 10. Dotte~ curve 11 designates the crowbar trip characteristic of a prior art crowbar network that responds solely to EHT. At the point where curves 10 and 11 intersect, the beam current of the CRT
is Ic. It can be seen from Fig. 2 that as long as the beam current is below Ic, the crowbar circuit will preclude operation in the forbidden zone. However, with beam currents greater than Ic, operation within the forbidden zone in the shaded area designated 12 is possible indicating that a crowbar network which responds solely to EHT is not satisfactory.
Still referring to Figure 2, curve 13 designates the V-I characteristic of a typical EHT power supply. In order to prevent nuisance triggering under various noise and transient conditions, at zero beam current curve ll-is preset to be at some predetermined level higher than curve 13. For example, a 6% differential between curves 11 and ! ... .
13 at ~ero beam current may be used. This 6% differential is not maintained at other beam currents, however, as may be seen by the divergence of curves 11 and 13.
;~ Curve 14 in Figure 2 designates the crowbar trip characteristic of a crowbar network embodying this invention '~ that is responsive not only to EHT, but also to beam current.
Like curve 11, it intersects the Y axis at a voltage 6%
above that at the intersection of curve 13 with the Y axis. `
However, unlike curve 11, curve 14 remains below curve 10 and between curves 10 and 13 regardless of beam current, . . ..
.` .
~ ~3_ ':' :
., .
: :
,: . ' ' . ~
so operation of the CRT within the forbidden zone is positively prevented.
Referring to Figure l, a low voltage regulator 16 which provides a D.C. output of, say, twenty-four volts, supplies the horizontal driver system 17 and other conven-tional components 18 of a television receiver, these com-ponents 18 being the tuner, I.F., video, audio, chroma, etc.
ne~works of the receiver. A.C. power is supplied to regulator 16 via a power transformer l9. Horizontal driver 10 system 17 includes an output transformer 21 having a flyback tertiary winding 20 that is connected to a voltage tripler 22 and a crowbar circuit 23. One output terminal of voltage tripler 22 is connected to the EHT button of a CRT. Tripler 22 also has an output terminal that is connected to crowbar circuit 23 so that a part of the EHT output of tripler 22 can be supplied to the crowbar circuit. The output of crow-, bar circuit 23 is supplied to low voltage regulator 16 and controls the output voltage thereof and hence the output voltage of horizontal driver systern 17.
Referring to Figure 3, crowbar circuit 23 includes a resistor Rl~ a resistor R2, a light emitting diode LEDl, a ~: capacitor C1 and a silicon controlled rectifier SCRl con-; nected as shown in the Figure. Voltage tripler 22 includes diodes Dl-D5, a resistor R3 and capacitors C2-C6 connected as shown in the Figure.
ReiEerring to Fig. l, a voltage which is directly proportional to the EHT developed at output terminals 25 of tripler 22 is developed at the other output terminal 24 of tripler 22 and is applied, referring now to Fig. 3, across 30 a voltage divider that includes the following serially con-nected components resistors R4 and R5, potentiometer Pl and resistor R6. The slider 26 of potentiometer Pl is connected to one electrode of a neon lamp 27.
i42~
The beam current of the CRT is drawn through a resistor R7 that is shunted by a capacitor C7. Consequently a voltage is developed across resistor R7 that is directly proportional to the beam current of the CRT, and this voltage is applied to the other electrode of neon lamp 27 via a resistor R8. Thus, from potentiometer Pl there is applied to one electrode of neon lamp 27 a voltage VA that is directly proportional to E~T and increases positively as EHT increases, while there is applied to the other electrode of neon lamp 27 a voltage VB that increases negatively with increasing beam current. The voltage VN across lamp 27 is equal to VA - VB, and when VN exceeds the trigger voltage of neon lamp 27, as a result of either an increase in EHT
or an increase in beam current or an increase in both, neon lamp 27 fires producing a pulse which is applied via a resistor R9 and a capacitor C8 to the gate electrode of silicon controlled rectifier SCRl turning on the silicon controlled rectifier. The turning on of the silicon con-trolled rectifier is signalled by illumination of light emitting diode LEDl and short ci:rcuits a portion of low voltage regulator 16 (Figure 1), thereby completely turning off the EHT. ~ecause the silicon controlled rectifier remains on after triggering, EHT remains off until the power has been removed, the originating fault rectified and power reapplied.
The time constant of resistor R7 and capacitor C7 is chosen to be substantially equal to that of the network supplying VA in order to maintain tracking and prevent false triggering during initial power application and during high ; 30 voltage arcing.
While in the embodiment shown a voltage VB that increases negatively witll increasing beam current is applied :.
.
to the righ~ hand electrode of neon lamp 27, alternatively it would be possible to apply to the left hand electrode of neon lamp 27 a voltage along with VA that increases positively with increasing beam current.
It is not essential to the invention that a neon lamp 27 be employed. Thus a diac, a Zener diode and asso-cia~ed circuitry or any other device or network that breaks down when a predetermined voltage is applied across it and then produces a trigger pulse could be used.
It also is not essential that a silicon controlled rectifier be used. The SCR could be replaced by its two 0 transistor equivalent circuit or by a flip-flop network.
It should be noted that the degree of V-I tracking, i.e., the slope of curve 14, can be controlled by varying the magnitude of resistor R7. Thus, if R7 = O, only EHT
will be tracked and curve 14 reverts to curve 11. Resistor R7 may be made variable, if desired, to permit the slope ,~ of curve 14 to be varied.
As an additional and preferred feature, but not essential to the invention in its broader aspects, there is provided an overcurrent detecting circuit 28 which is designed to protect the CRT in the event of a large beam overcurrent occurring. This circuit is constituted by resistor R10;, capacitor C9, zener diode Zl, transistor TRl and its associated resistors Rll - R13. The beam current at which circuit 28 activates is determined by the value of resistor R7 and the trigger voltage of zener diode Zl. When the beam current is sufficiently large to produce a voltage : across resistor R7 that is greater than the zener voltage of zener diode Zl, the latter will fire turning off transistor ; -6-~ 6~
TRl and triggering silicon controlled rectifier SCRl so as to cause the EHT to drop to zero.
It should be noted that the entire crowbar circuit 23 could be replaced with MOTOROLA (trade mark) IC MC3423 or MC3523, particularly where VA and VB are applied to the same sensing input.
It also should be noted that the desired result can be achieved other than by turning off the EHT for the CRT. Thus, operation of the crowbar circuit could be arranged to turn off the beam current of the CRT at the ~ cathode thereof, to bias Gl of the CRT negative, thereby ; interrupting beam current, to cause the frequency of the high frequency oscillator to go out of sync and increase in frequency, causing EHT to decrease. In addition, flow of current through the SCR could be arranged to blow a power supply fuse.
While a preferred embodiment of the invention has been disclosed, those skilled in the art will appreciate that changes may be made therein without departing from the spirit and scope of this invention as defined in the - appended claims.
.
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.- ~ .
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination with a cathode ray tube having means for supplying EHT thereto and an EHT vs. beam current characteristic defining on one side of said characteristic an undesired mode of operation and on the other side of said characteristic a desired mode of operation, means for inhibiting operation of said cathode ray tube on said one side of said characteristic, said inhibiting means com-prising means for deriving voltages proportional to both the EHT supplied to said cathode ray tube and the beam current of said cathode ray tube, means for supplying said voltages to a sensing device, said sensing device being adapted to produce a trigger pulse when the voltage across said sensing device exceeds a predetermined magnitude, said sensing device being selected such that said trigger pulses always occur at an EHT and beam current value that is on said other side of said character-istic and means responsive to the generation of said trigger pulse for inhibiting the operation of said cathode ray tube, by interrupting the supply of EHT from said supplying means to said cathode ray tube.
2. The combination according to Claim 1 wherein said sensing device is a neon lamp.
3. The combination according to Claim 1 wherein said responsive means is a silicon controlled rectifier.
4. The combination according to Claim 3 wherein said sensing device is a neon lamp.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA278,305A CA1086420A (en) | 1977-05-11 | 1977-05-11 | Networks for limiting x-radiation from cathode ray tubes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA278,305A CA1086420A (en) | 1977-05-11 | 1977-05-11 | Networks for limiting x-radiation from cathode ray tubes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1086420A true CA1086420A (en) | 1980-09-23 |
Family
ID=4108654
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA278,305A Expired CA1086420A (en) | 1977-05-11 | 1977-05-11 | Networks for limiting x-radiation from cathode ray tubes |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1086420A (en) |
-
1977
- 1977-05-11 CA CA278,305A patent/CA1086420A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |