KR840000872B1 - Stylus position sensor for video disc player apparatus - Google Patents

Abstract

A stylus poisition sensor for a video disc player apparatus has an electrode secured in fixed relation to a movable stylus, which is disposed between the apparatus first and second electrodes to form first and second variable capacitors. The capacitance of the variable capacitors changes in accordance with the motion of the stylus-related electrode. A time-varying signal is applied through fixed impedances to the first and second electrodes. The amplitude of the signal is modulated by voltage variable impedance, connected between the first and second electrodes, and a point of fixed potential.

Description

Video Disc Needle Position Detector

1 is a partial schematic and block diagram of the balance needle position sensing device.

2 is a graph of signal amplitude versus needle travel at many circuit connection points in the apparatus of FIG.

3 is a partial schematic diagram and block diagram of a synchronous detector driving circuit.

4 is a block diagram of an addition circuit and an average circuit for processing a detector signal.

5 is a block diagram of a circuit for detecting a detector signal and generating an oscillation signal.

6 and 8 are a partial schematic and block diagram of a balanced signal pick-up needle position detection device constituting the present invention.

FIG. 7 is a graph of full width time showing the potential applied at the sensor electrode of FIG. 6. FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video disc signal pickup device, and more particularly, to an apparatus for determining a relative position of a signal pickup needle relative to a carriage assembly for moving a pickup needle radially traversing a disc record.

In any type of video disc system using disc records, information is pre-recorded by geometric changes in tracks or grooves on the disc surface. This information is reproduced by a signal pick-up needle which detects a geometric change representing a pre-recorded signal in contact with a track or groove. In a capacitive system, needle-record interactions cause time-varying capacitances to form when the geometric change of a particular track moves the needle by disk rotation, which is part of the tuning circuit for amplitude-modulating the carrier frequency. Form. This amplitude modulation is then converted into video and audio signals suitable for detection and reproduction on a standard receiver.

In a compression sensing system, the geometrical change of the groove applies a time varying force to the needle mechanically coupled to the compression sensing transducer for changing into an electronic signal.

In this type of video disc system, disc records having a track or groove density of 6000 to 10000 / inch are used. Such high groove density makes it difficult to reliably move the needle radially traversing the disk in accordance with normal operation. Thus, the signal pickup needle is mounted in the carriage assembly driven by the drive means to move the needle radially traversing the disk simultaneously with the rotation of the disk. Since the tracks tend to be slightly eccentric, the needle is mounted in the carriage, limiting the radial movement of the needle relative to the carriage. Such relative movement mechanically biases the needle mounting arm from its initial position and has an undesirable effect on the needle deflector, which provides stop motion and other special effects. To compensate for this condition, the relative needle position relative to the carriage assembly is adjusted, the carriage movement is controlled so that the needle arm remains unbiased and the needle is centered on the track.

Such a needle position adjustment system is mentioned in U.S. Patent Application No. 055,976, entitled Needle Position Sensing Device for a Video Disc Player, filed July 9, 1979. The present invention detects the needle position by the following method.

a) setting the capacitance between the first electrode fixed to the carriage and the second electrode fixed to the needle

b) measuring the capacitance change caused by mutually changing the first electrode and the second electrode,

c) detecting the relative amplitude of the oscillation signal coupled from the first electrode to the second electrode,

d) by generating a control signal proportional to the combined signal. However, the performance of this system can be influenced by changes in parasitic parameters present between the needle-needle-record apparatus and the change in the active gain element of the apparatus. The change in parasitic variables affects the amplitude of the oscillating signal coupled from the first electrode to the second electrode, resulting in an error in the control when the combined signal is measured against a fixed reference.

The present invention relates to a balance detection system wherein two signals from two electrodes arranged on one side of a third electrode fixed to a needle are applied as complementary signals to the third electrode. The two signals are connected to a third electrode that is proportional to the capacitance change formed between the two electrodes, and are arranged to sum up to zero when the third electrode and the needle thereby are in a predetermined position. The third electrode moved at the predetermined position changes the sum signal having an amplitude and a phase representing the range and direction of the movement operation.

In Fig. 1, the signal pick-up needle 11 is in contact with a record disk 10 for a reproduction signal previously recorded in a track located on the surface of the disk. The signal on the disk is applied to the pickup circuit 22 to generate a modulated frequency or FM signal via the needle and connection leads 21 and 21. The FM signal is additionally processed by the circuit 24 to be adjusted for reproduction on the TV receiver 25. The needle 11 is secured to a needle arm (not shown) that is flexibly mounted to a carriage assembly for radially traversing the record disk, i.e., in the X-axis direction shown in the figure. Mounting the needle arm to the carriage assembly can be made directly to the carriage assembly or detachably mounted to a cartridge within the carriage assembly. The element 8 represents a support member fixed to a cartridge or carriage assembly and is disposed on one side of the needle / needle arm assembly. The support member fixed relatively closely to the needle is the first conductive electrode 14 and the second conductive electrode 15. The third electrode 13 is a needle positioned between the first and second electrodes 14 and 15. It is fixed to the needle arm assembly. The third electrode 13 is limited to move in accordance with the needle motion in the X 'direction. The electrode 13 may be a portion of the fly lead which is electrically connected to the lead lid 12 for separating the conductive element fixed to the needle arm and electrically connecting the needle to the pickup circuit or moving in line with the needle.

관계에 따라 용량이 감소될때 증가한다. 여기에서 ε는 공기의 허용도이고 A는 전극(14)(15) 각각에 인접하면서 평행인 전극(13)의 영역이며, d는 전극(14)(15)간의 거리의 1/2이며, X는 전극(13)이 중심위치로 부터 떨어진 거리이다. 전극(14)(15)간 중심에 위치한 전극(13)에 대해 ＂X＂는 제로이고 제1, 제2캐패시터는 동일한 용량치를 갖는다.The first electrode 14 and the third electrode 13 constitute a plate of the first variable air dielectric capacitor, and the second electrode 15 and the third electrode 13 constitute a plate of the second variable air dielectric capacitor. The first and second variable capacitor capacitances are changed according to a similar auxiliary method such that the third electrode moves in the direction of X X with respect to the element 6 fixed to the carriage assembly. The capacity of the first (second) capacitor is that the second (first) capacitor

It increases when the dose decreases, depending on the relationship. Where ε is the tolerance of air and A is the area of the electrode 13 adjacent and parallel to each of the electrodes 14, 15, d is 1/2 of the distance between the electrodes 14, 15, and X Is the distance away from the center of the electrode 13. For the electrode 13 located at the center between the electrodes 14 and 15, XX is zero and the first and second capacitors have the same capacitance value.

Signal source 7 generally provides a time-varying signal of oscillation characteristics, which is a sinusoidal or square wave or a regular wave, which is an arbitrary waveform. Here the signal source 7 generates a signal that changes formally. The signal source 7 applies the first signal V ₁ to the electrode 15 via an impedance 17. The signal from the signal source 7 is operated on the circuit 20 to form a signal V ₂ which is complementary to the signal V ₁ and the signal V ₂ is applied to the electrode 14 via an impedance 16. do.

Here, the complementary signal means a signal defined as a signal whose polarity is inverted with respect to a given reference polarity. In the case of a regular oscillation signal of constant frequency, the complementary signal with this signal is the same signal having a phase difference of 180 degrees. In this application, the amplitude of the signal and its complementary signal need not be the same. Only when it is desired that the physical parameters of the balancer are the same on both sides of the center pole and the needle is null in the exact center between the two fixed electrodes, the amplitude of one signal and its complementary signal will be the same.

The signals V ₁ and V ₂ applied to the electrodes 14 and 15 are logarithmically dissipated at the electrode 13 by the combination of the first and second capacitors. With the amplitude of the signal V ₁ equal to the amplitude of the signal V ₂ , the sum of the signals V ₃ is zero with respect to the electrodes 13 disposed at the same distance from the electrodes 14, 15. do. When the electrode 13 is displaced from the center position and approaches the electrodes 14 and 15, the amplitude of the potential V ₃ increases and thus becomes the phase angle of the signal closer to the electrode. The amplitude and phase of the potential V ₃ represent the range and direction in which the needle 11 is moved relative to the element 8 (see FIG. 2) to which it is fixed.

캐패시턴스관계에 의해 사실상 선형이 아니고 중심전극의 작은 편차에 대해 용량의 변화는 거리(X)와 선형함수 관계가 이루어진다.In FIG. 2, the potential V ₁ (V ₂ ) has a constant amplitude in the opposite phase and is independent of the garlic position. The sum V ₃ of the signals V ₁ and V ₂ coupled to the electrode 13 becomes zero when there is no deviation from the center position (zero), and when the needle is shifted to one side of the center position. The amplitude of the sum V ₃ increases. The phase of V _{3 will be} in phase with V ₁ to the left of the center and in phase with V ₂ to the right of the center. So the sum of (V ₂ + V ₃ ) is equal to V ₂ because V ₃ is zero at the center position, and on the left side of the center it decreases because V ₂ and V ₃ have a 180 ° phase difference, and the right side of the center Increases because V ₂ and V ₃ are in phase. The sum of the curves V ₃ (V ₂ + V ₃ ) is shown linearly in FIG. 2, which is obtained when the pickup circuit 22 is linear or voltage invariant. On the other hand, if the circuit 22 has nonlinear input characteristics, the curve V ₃ (V ₂ + V ₃ ) will exhibit nonlinearity and means are needed to compensate for such nonlinearity. (V ₃ ) and (V ₂ + V ₃ ) are

Due to the capacitance relationship, the change in capacitance is linear in relation to the distance X for a small deviation of the center electrode, which is not substantially linear.

The signal V ₃ processed by the pickup network 22 is a composite signal including the FM signal recorded in advance on the disc combined with the sum of the signals V ₁ (V ₂ ). This synthesized signal is applied to the bandpass filter 26 at the terminal 23. The bandpass filter 26 passes only the frequency components attributable to the signals V ₁ and V ₂ to the output terminal 27. The passed signal is applied to the processing circuit 29 at the terminal 27 in which the signal is detected and buffered to modulate the potential applied to the carriage drive motor 31.

3 shows a specific circuit 29 for realizing the function of the motor drive processing circuit 29. As shown in FIG. This circuit consists of a synchronous detector and a shock absorber / driver 40. The shock absorber / driver 40 responsive to the D and C potentials applied to the input terminal 42 by the power source 43 drives the motor 31 to drive a carriage that radially traverses the discrec- tion at the same time as the disc rotation. A rated signal is generated at its output 30 which activates.

The signal at the output 30 of the shock absorber / driver 40 is increased or decreased in accordance with the calibration signal applied to the second input terminal 41. The synchronous detector includes a transistor switch 36 that opens and closes in phase with one of the signals applied to the electrodes 14 or 15. This signal is applied to terminal 28 and regulated by amplifier 37 to drive the control electrode of the transistor against rapid transitions between conductive and non-conductive. The sum signal V ₃ is applied to the terminal 27, and selectively applied to the capacitor 39 -resistor 38 combination by the transistor switch 36 at the terminal 27. While the switch 36 is closed, the capacitor is discharged through the resistor 38. The composite potential on the capacitor 39 applied to the terminal 41 tends to be the average value of the half-wave rectified signal V ₃ . This composite potential is positive if the signal applied to the terminals 27, 28 is in phase, and negative if the phases are different. Therefore, the synchronous detector can shear the bidirectional signal for controlling the shock absorber 40. Conversely, capacitor 39 and resistor 38 may be restored to a reference potential defined differently from the ground reference if the potential at terminal 41 is changed relative to the regulatory reference to control buffer 40. .

4 is a schematic diagram of the replacement detection circuit 29 '. In this circuit, the amplifier 49 sums the signals applied to the terminals 27 and 28 and at the terminal 50, V (50) = V (27). R (47) / R (45) + V (28). AC output potentials represented by R (47) / R (46) are generated. Where V (50), V (27) and V (28) are the signal amplitudes at terminals 50, 27 and 28 respectively, and R (45), R (46) and R (47) are resistors. (45) (46) (47) are resistance values of each. If the signal V ₃ applied to the terminal 27 has a zero value corresponding to the needle at the center of the signal, the potential at the output terminal 50 of the amplifier 49 is applied to the terminal 28. It is proportional to the signal (V ₁ ) or (V ₂ ) and has a constant rated amplitude. This signal is detected by a diode detector consisting of a diode 52, a capacitor 53, and a resistor 54 and then buffered in the circuit 51 before being applied to the output terminal 30. When the needle is positioned away from the center position, the amplitude of the signal at the terminal 50 is modulated by the signal applied to the terminal 27. If the signal at the terminals 27 and 28 is in phase, the amplitude of the signal at the output terminal 50 increases above the rated value and decreases when the phase is different. The DC output potential at the terminal 30 increases and decreases corresponding to the increase or decrease of the AC signal amplitude at the terminal 50 shown by the curve V ₂ + V ₃ in FIG. The DC potential applied to the non-converting input terminal of the amplifier 49 by the front panel 48 adjusts the rated DC potential appearing at the output terminal 30.

5 shows the oscillator 7 and the processing circuit of the Motorola MC1357 or Al. Seed. A method is realized using commercially available integrated circuits such as Eisa's CA211FM limiter and a balanced detector. The numbering in the figure shows the number of package connection pins for the double inline plastic package of standard (14). The red detector uses the first input signal V ₃ derived from the pickup circuit and the second input signal obtained from the limiting amplifier connected to the ceramic filter to form an oscillator useful for driving the electrodes 14, 15. It is used as a synchronous detector having.

6 is a second embodiment of the balanced position sensor, wherein the oscillation signals applied to the two fixed detector capacitor electrodes have the same phase, while their amplitudes are asymmetrically modulated by a similar complementary method.

As a result of the in-phase signal being applied to the fixed electrodes 76 and 78, the signal component coupled to the third electrode 77 is not added to zero for the needle at the zero position. In order to make the zero signal effective, the applied signal is arranged so that the time average of the signal added by the third electrode 77 is equal to zero. In this arrangement, the time average of the sum signal becomes the absolute value of the sum signal.

The amplitude modulation of the signals applied to the first and second electrodes is effective at the first and second electrodes by first and second voltage variable impedance means connected between the electrode and the reference potential point, respectively. The voltage variable impedance means is arranged such that a change in the effective impedance of the first variable impedance is complementary to the effective voltage of the second variable impedance. That is, the first variable impedance value increases simultaneously with the decrease of the second variable impedance, and the first variable impedance value decreases simultaneously with the increase of the second variable impedance. The variable impedance may be in the form of a capacitive resistor or the like and its impedance value is chosen so that the needle-record disk-pickup circuit arrangement is not loaded.

In FIG. 6, the AC signal from the power supply 61 is applied to the fixed capacitor electrode 78 through the potentiometer 63 and the resistor 67, and fixed through the potentiometer 63 and the resistor 65. In FIG. Is applied to the capacitor electrode 76. (The potentiometer 63 is used to adjust the signal at the electrodes 76 and 77 to generate a zero signal at the center electrode 77 to have the center electrode 77 at a predetermined position). The first voltage variable impedance or VVI 69 has a first end connected to the capacitor electrode 76 fixed at the contact 68 and a second connected to the reference potential at the terminal 71 via a bias potential 70. Has an end. Similar to 69, the second VVI 73 has a first end connected to the capacitor electrode 78 at the contact 74 and a second end connected to the reference potential of the terminal 71 via a bias potential 72. Have VVI 73 is polarized in contrast to VVI 69 such that the potential change applied by the front panel 61 produces a complementary impedance change of VVI 73 and VVI 69.

VVI 69 and resistor 65 function as a function of the voltage applied to electrode 64 to the alternating potential at electrode 76, i.e. V (76) = V (64) {Z (69) / [Z (69) + R (65)]}. Where V (76), V (64) represent the potentials at electrode 76 and contact 64, respectively, Z (69), Z (65) are the impedances of VVI69 and resistor 65 and Resistance. Similarly, the potential V 78 at the electrode 78 is represented by V (78) = V (66) {Z (73) / Z (73) + R (47)]}.

It is assumed that the potential V 64 is the same as the potential V 66 and the potential signal from the power supply 61 is a sine wave (waveform V 62 in FIG. 7). The half period positive polarity of the waveform appearing at the contact 68 is due to the increase in the impedance of the VVI 69, and the semi period periodicity is due to the impedance decrease. Thus, the potential V 76 is more proportional to the positive polarity of the half period of 64 than the negative polarity of the half period of V 64. Conversely, the potential V 78 is more proportional to the negative polarity of the half period of V 66 than the positive polarity of the half period of V 66. This effect is illustrated by waveform (b) in FIG. 7, where it can be seen that the maximum potential for the alternate half-cycle cycles of V 76 and V 78 is compressed and stretched.

Considering the potentials V76 and 78 having the same residual width as the center electrode 77 at the same distance from the electrodes 76 and 78 but having an asymmetric waveform polarity, the average value of the potentials applied to the electrodes 77 In other words, the average sum of the compressed half cycles is zero and the average sum of the uncompressed half cycles is zero. Since the control electrode is located away from the center or zero position, the average value of the signal applied to the electrode 77 is increased or decreased. Considering the case where the electrode 77 approaches the electrode 78, a larger proportional portion of the signal V 78 and a smaller proportional portion of the signal V 76 are applied to the electrode 77. The average of the signal V 78 itself is negative and the sum of the signals [V 78 and V 76] equally coupled to the electrode 77 is zero and thus the electrode 77 approaching the electrode 78. The state of must generate a sum signal with a negative mean value. On the other hand, the signal V 76 itself is positive and the electrode 77 located close to the electrode 76 generates a sum signal having a positive mean value. Therefore, the average signal value represents the movement amount of the electrode 77, and the polarity represents the movement direction of the electrode. Bias potentials 70 and 72 are expressed when used to adjust specific voltage variable impedances for operating characteristics within their predetermined operating range.

The detector 87 of FIG. 6 is in the form of determining or responding to a change in the mean value. For example, a lowpass filter can function even if the response is slow. More preferably, the balanced synchronous detector or red detector shown in FIG.

The second operable mode for the circuit of FIG. 6 is efficient by arranging the WI devices 73 and 69 and the variable air capacitance directly interacting with the signal pickup circuit to generate a control signal proportional to the needle position. do. In such a mode, the pickup circuit does not respond to the signal from the power supply 61, that is, the time-varying voltage or the modulation component of the time-varying voltage applied to the third electrode. The pickup arc generates a signal responsive to the instantaneous impedance present at its input. The device itself is generated as a control signal having an absolute zero rather than a time average of zero as described above. A particular embodiment using this technique is shown in FIG. 8, and the operation of this embodiment generally shows a second mode of operation for the position sensing circuit.

The embodiment of FIG. 8 is a specific application of a balance detector using varactor diodes as voltage-variable impedances in a pick-up video disk device. In FIG. 8, the circuit 200 shown in dashed lines is pre-set from the record disk 145. In FIG. A specific signal pickup circuit is shown which cooperates with the needle-record capacity 143 to reproduce the recorded signal. The capacitor 143 is an effective capacity formed between the needle 144 and the record disk and varies depending on the type of starvation in the disk groove through which the needle passes. The capacitor 143 is connected in parallel with the capacitor 114 and the inductor 115 to form a parallel vacuum circuit or a tank circuit. The coil 116 driven by the oscillator 117 having a sinusoidal wave of 915 MHz is connected to the tank. Inductively applying the signal to the tank circuit at a frequency slightly above or slightly below the rated resonant frequency of the circuit. More precisely, the signal from the power source 117 interferes with the amplitude-frequency characteristics of the tank circuit at half of its maximum. Due to the change in the capacitance of the capacitor 143 due to the recorded signal, the resonance frequency of the tank circuit generating the oscillation signal is changed in order to amplitude-modulate according to the already recorded signal. The amplitude modulated oscillation signal is picked off the tank circuit by the coil 118 and applied to the detector circuit consisting of the dial 150 and the resistor-capacitor coupling 152, 151. This detector circuit removes the oscillation signal generated by the power supply 117, and supplies a signal representing the pre-recorded signal of the record disk to the contact point 119. This signal is processed by the audio and video circuit 120 and delivered to a standard receiver.

On the system described above, the balanced needle position sensor is more effective by using the electrodes 105, 106 and 109 to form the position sensing capacitances 107 and 108. The first varactor diode 103 connects the capacitance 108 in series with the reference potential 10 and the second varactor diode 104 connects in series with the reference potential 102. The effective capacitance of the varactor diode 103 and the series connection of the capacitor 108 and the effective capacitance of the capacitor 143 and the varactor diode 104 and the series connection of the capacitor 107 are effectively connected in parallel with the capacitor 114. It can be operated to change the resonant frequency of the tank circuit.

The oscillation signal from the power supply 113 of the 262 kHz sinusoidal wave applies a time shift to the anode of the varactor diode 104 and the cathode of the varactor diode 103 through the resistors 110 and 111, which is a time shift. This results in modulation of the effective capacitance of the varactors 103 and 104. The capacity of the varactor 104 increases (decreases) when the capacity of the varactor 104 decreases (increases). The total capacitance avoided by the varactor diodes across the tank circuit coil 115 remains constant as long as the capacitances 107 and 108 are the same and the varactors are similar and have a linear capacitance-voltage relationship. While the capacitance of the position sensing element remains constant, a zero signal is contributed from the oscillator 113 at the output 119 of the detector 150, and therefore an absolute zero can be realized.

Therefore, the movement of the needle and the center electrode 109 will cause an increase (decrease) in the capacitance 107 and a decrease (increase) in the capacitance 108. Considering the increased capacitance 107 by the rightward transfer of the needle, the capacitance 107 increases and the capacitance indicated by all capacitors across the tank circuit is time synchronized to the semi-periodic negative signal from the front panel 113. It becomes bigger by accomplishing Conversely, the left-hand transfer of the needle is made larger by synchronizing time with the half-cycle positive signal from the front panel 113. These capacity modulations cause amplitude modulations of the signal applied to the tank circuit from the front panel 117 in a form similar to record disk induction modulation. Therefore, the capacitance modulation and the amplitude modulation amount of the carrier signal thereby indicate the movement range of the needle and the phase of the final signal indicates the movement direction.

The prerecorded signal and the movement induction signal form a combined signal obtained at the contact point 119. The movement induction signal is extracted from the synthesized signal by the band pass filter 130 and detected by the synchronous detector 140 to generate a DC control signal at the output terminal 142.

In the system shown in FIG. 8, other elements besides the varactor may be used as the voltage variable impedance element. An important requirement imposed by the system is that the prime reactance imposed by the position sensing element across the tank 114 of the capacitor 114 and coil 115 must remain constant with respect to the zero position of the electrode 109.

Each of the signals from the front panels 61 and 113 of FIGS. 6 and 8 can be applied to the fixed capacitor electrode via the voltage variable element as shown in the figure by simply exchanging VVI and resistance. For example, in FIG. 8, the electrode 110 having the resistor 110 connected between the bias 101 and the electrode 105 and the anode of the varactor connected to the power supply 113 is connected to the power supply 113. Like the varactor 103, the varactor 103 and the resistor 110 may be interchanged. Similarly, the varactor 104 and the resistor 111 may also be exchanged, in which case the cathode of the varactor 104 is connected to the front panel 113. There is an advantage in the method used to connect the power supply to the voltage variable element and the capacitor electrode depending on whether the system used is signal (ie voltage) sensing or impedance sensing.

In addition, it should be noted that the variable impedance is not limited to the voltage variable form. For example, a variable current impedance, such as a saturable reactor, can be used in certain devices.

Claims (1)

The first electrodes 77 are fixed to the first elements 79 to be the same together; The second electrode and the third electrode are fixed to each other through the second elements 63 and 65 and 63 and 67, and are arranged on both sides of the first electrode so that the first and third electrodes have a first variable capacitor capacity. The third electrode has a second variable capacitor capacity; A video disc needle position sensing device having a pick-up network for generating a signal indicative of a relative position of a first element for sensing a relative position of a first element relative to a second element, wherein the time-varying signal source 61 is connected to the first and the second element; A second voltage variable impedance (69) (73); and a first voltage variable impedance (69) connected by the first variable capacitance (76) (77) to a first linear impedance combination (68). Increasing or decreasing the impedance value of the first series impedance combination with respect to the time varying signal source having a monopolar and second polar signal; The impedance value of the second series impedance combination with respect to the time varying signal source is increased by the contact point 74 connecting the second voltage variable impedance 73 to the second variable capacitance 78 and 77 and the second series impedance combination. Simultaneously reducing or reducing the first and second series impedance assemblies in parallel with the first electrode 77; As a function of the relative position of the first element relative to the second element, the pickup circuit 82 and the detector 87 in response to the impedance value by parallel connection with the first and second series impedance assemblies are connected to the first electrode. A video disk needle position sensor device for generating a position signal of a third electrode due to the impedance.

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