JPS6124867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image display device having a linear hot cathode, and particularly to an image display device that can extract a uniform electron beam from the linear hot cathode.

Conventionally, devices using EL, plasma, liquid crystal, etc. have been developed as matrix-type flat display devices, but they have not been able to achieve sufficient performance in terms of brightness, luminous efficiency, color display, etc. Image display such as motion has not yet reached the point of practical use.

On the other hand, attempts have been reported to construct flat display devices using electron beams. That is, this device displays characters or images by controlling the electron beam emitted from an electron source using a flat matrix type electron beam control electrode.

FIG. 1 shows an example of a main part configuration diagram of this type of display device. 1 is a flat electron source, and a hot cathode, a field emission cold cathode, etc. are used. Reference numeral 2 denotes a grid-like electrode plate having a large number of through holes 6, through which a positive voltage is applied to the cathode 1 and an electron beam is extracted. A part of the electron beam passes through the through holes of the grid electrode plate 2,
The electron beam reaches the surface of the electron beam control electrode plate 3. A large number of through holes 6a and 6b are regularly drilled in the control plates 3 and 4, vertically and horizontally, and strip-shaped electrodes 7 and 8 are provided in each row and column, so as to be perpendicular to each other. Through holes 6a, 6 are provided in both electrode plates at appropriate intervals and at each orthogonal intersection.
b are arranged so that they match. The beam current of the electron beam that has reached the surface of the electron beam control electrode plate 3 is modulated in accordance with the signal voltage applied to each strip-shaped electrode 7, and passes through the through hole 6a to reach the surface of the electron beam control electrode plate 4. reach Regarding the electrode plate 4, the electron beam is modulated by the same mechanism as the electrode plate 3 and passes through the through hole 6b. Through hole 6b
The electron beam that has passed through is accelerated by a positive high voltage applied to the accelerating electrode plate 9, collides with the phosphor film 11 coated on the surface of the accelerating electrode 9, and emits light. Generally, a focusing electrode plate is provided between the electron beam control plate 4 and the accelerating electrode plate 9 to focus or collimate the electron beam and to prevent the potentials of the control electrodes 3 and 4 from being affected by the high voltage for acceleration. Insert 5.

In the display device configured in this manner, characters or images can be displayed by sequentially applying signal voltages to each electrode of the electron beam control electrode plates 3 and 4. 10 is a transparent glass substrate.

In general, in this type of display device, a so-called matrix type display device, the resolution of the image is determined by the size and pitch of the through holes provided in the electron beam control electrode or its substrate. Therefore, the higher the resolution and the clearer the image, the smaller the diameter of the through holes and the smaller the pitch. When trying to obtain a clear image of a certain size, the through holes 6a,
6b and the electrodes 7 and 8 must be arranged at a higher density, and the number of holes and the number of electrodes must be significantly increased. For example, to display a TV image, a minimum of 500 x 500 through holes are required, and each electron beam control electrode plate requires 500 electrodes. Furthermore, when I try to display in color, 3
Requires twice as many through holes and electrodes.

2-3 per mm with current materials and processing technology.
Books are said to be the limit, and sufficient resolution cannot be obtained. Furthermore, increasing the number of holes and electrodes significantly increases the number of drive circuits for driving each electrode and the number of connection points between the drive circuit and each electrode, which poses a major problem in mounting.

As a method for solving the above problems, US Pat. No. 3,935,500 discloses a method in which the electron beam is controlled by a pair of matrix electrodes and deflected vertically and horizontally by deflection electrodes. In the above-mentioned US patent, one hot cathode is provided as a cathode in each through hole formed in the matrix electrode, so the electric power for heating is significantly large.
In addition, variations in emitted electron current between individual cathodes pose a major problem in practice.

The present invention solves the above-mentioned problems, and provides a flat image display device that can provide a high-brightness, high-resolution screen, has excellent brightness uniformity, is easy to assemble, and has high industrial value. .

FIG. 2 shows a partially exploded perspective view of the basic configuration of the flat image display device of the present invention. Reference numeral 20 is a linear hot cathode, which is a tungsten wire of 10 to 20 μm and coated with an oxide cathode material. Reference numeral 21 denotes a U-shaped or U-shaped partition electrode, which is arranged so as to cover the periphery of each linear hot cathode except for the front side. The structure is such that a high-density electron beam flows into the through hole 22a. A series of through holes 22a formed in the electrode 22 for extracting the electron beam are formed in parallel and opposite to each linear hot cathode.

23 is a plurality of strip-shaped electrodes, and a through hole 23a is formed coaxially with the through hole 21a formed in the electrode 22. electrodes 24 and 25
is an electrode for shaping an electron beam, and through holes 24a and 25a are formed coaxially with through holes 22a and 23a formed in the electrodes 22 and 23. The electrode 26 and 26' form a pair to constitute an electrode for vertical deflection. Similarly, 27 and 27' are electrodes for horizontal deflection. The electrode 28 is a grid-shaped electrode and serves as an electric field shielding electrode to prevent the influence of the high voltage applied to the electrode 29 for accelerating the electron beam from adversely affecting the deflecting electrodes 27 and 27'. It is. Reference numeral 31 is a transparent glass substrate, on the surface of which is coated a phosphor layer 30 that emits light when an electron beam collides with it, and on the surface of which is deposited an aluminum thin film 29, which is displayed at the same time as the accelerating electrode. It makes up the surface.

Each electrode component will be described in detail based on the results of a display device having a 5-inch display surface in a flat display device having the above basic configuration.

Cathode Section FIG. 3 shows the configuration near one linear hot cathode 20 in FIG. 2. A linear hot cathode 20, a partition electrode 21, and an electrode 22 for extracting an electron beam
The cathode section is configured by The linear hot cathode 20 is
Three-component oxide cathode material (B _a , S _r , C _a ) CO ₃ is electrodeposited on a 20 μm tungsten wire to a thickness of 10 to 20 μm, and 15 wires are strung horizontally at 5.08 mm intervals. ,
One linear hot cathode illuminates one-fifteenth of the display surface,
The configuration is such that 15 beams irradiate the entire display surface with electron beams. Each linear hot cathode 20 needs to be stretched with an appropriate tension so as not to sag during operation. Each linear hot cathode 20 is stretched approximately at the center of a U-shaped or U-shaped cylindrical partition electrode 21,
A plate-shaped electron beam is formed by a focused electric field formed by the partition electrode 21 and the electrode 22 for extracting the electron beam. In addition to the shape described above, the partition electrode 21 can be formed of a parallel plate and serves as a back electrode of the linear hot cathode 20.

The electrodes 22 for extracting the electron beam are metal conductor plates, and are arranged in parallel to each linear hot cathode 20.
Eighty-one through holes 22a with a hole diameter of 0.8φ are bored at a pitch of 1.27 mm.

FIG. 3 shows a wiring diagram of the cathode section of the present invention. The cathode section shown in FIG.
This method was proposed in the No. 2003 issue, and is intended to obtain an electron beam with a uniform and high current density. One end of the linear hot cathode 20 is connected to the positive electrode of the electrode _V1 via a resistor R. The other end of the hot cathode 20 is characterized in that it is connected to the negative electrode of the power source V ₁ via a diode 32 . 33 is a negative pulse voltage generator.
A negative voltage is applied to the cylindrical electrode (partition electrode) 21 by a power source _V2 , and a positive voltage is applied to the electrodes 22 and 23 by power sources _V3 and _V4 , respectively.

When the linear hot cathode 20 is supplied with power by the power source V ₁ , the hot cathode 20 is in a state where it can emit electrons, but
Although a positive voltage is applied to the electrode 22, since a negative voltage is applied to the cylindrical partition electrode 21, no electrons are emitted. In other words, it can be considered that a bias voltage is applied to the electrode 21 to prevent electron emission.

Note that when a negative voltage is applied to the partition electrode 21, the linear hot cathode 20 can be maintained in the open state over the entire length. The reason is that one end of the linear hot cathode on the diode 32 side is at 0 potential,
Since a positive potential is applied to the electrode 22, at first glance it seems that the diode 32 side of the linear hot cathode 20 is not in a cut-off state, but the partition electrode 2
1 is negative, the vicinity of the linear hot cathode 20 can be held at a negative potential with respect to the cathode (due to the negative potential of the partition electrode 21), and electrons are not emitted from the linear hot cathode 20. It is possible to do so.

However, in this state, when a negative pulse voltage is applied to one end of the hot cathode 20 by the pulse voltage generator 33, the hot wire cathode 20 becomes negative and electron emission occurs. At this time, the diode 32 is in the opposite direction at the other end of the hot cathode 20, so that the potential difference between both ends of the hot cathode becomes approximately 0, and there is no potential gradient in the axial direction. Therefore, it is possible to obtain an electron beam that is uniform and has a high current density.

FIG. 4 shows measured values of the electron beam current flowing through each electrode using the connections shown in FIG. I ₂ , I ₃ and I ₄ represent electron beam currents flowing through electrodes 21, 22 and 23, respectively. When V ₃ is +20V, V ₄ is +60V, and the pulse voltage is -20V, the cylindrical electrode 21
This is the measured value when changing the bias voltage.
Note that the cross section of the cylindrical electrode 21 is, for example, 5 mm x 5.08 mm.
mm, and was measured with a linear hot cathode 20 stretched and fixed at its center.

As is clear from FIG. 4, when the voltage applied to the cylindrical voltage 21 is lower than about -11V, no current flows, and all of the current flows into the electrode 22, and part of it flows into the through hole 22a provided in the electrode 22 (the effective area is Electrode 22
8%) and flows into the accelerating electrode 23.

When the potential of V ₂ is -10V, -20V and -30V, the beam current I ₄ passing through the through hole 220 of the electrode 22
(Current flowing through the electrode 23) is the electron beam current emitted from the linear hot cathode 20 (total of I ₃ and I ₄ )
The values are 13%, 35%, and 59%, indicating that the utilization rate of the electron beam current increases. The cause of this is the three electrodes 21, 22, 2 that constitute the cathode section.
3, a hanging glass-like equipotential surface with the linear hot cathode 20 at its apex is formed, and the electron beam is directed to the through hole 2.
This is because the light is focused in a plate shape at the portion 2a.

Next, improvements in the uniformity and density of the electron beam in the electron source shown in FIG. 3 will be explained with reference to FIGS. 5 and 6. Figure 5 shows the uniformity of the electron beam extraction method of the present invention and the conventional method when a cathode heating voltage of 6 V is applied to the hot cathode 20 with a length of 12 cm and +10 V is applied to the electron extraction electrode 22 which is the counter electrode. This is a comparison. FIGS. 5a and 5b show the potential difference and the relative value of the electron beam current at positions along the length of the linear hot cathode, respectively. The curves are for the present invention and curves are for the conventional case. As is clear from this figure, when an electron beam is emitted by simply applying a predetermined voltage to one end of the hot cathode, which has been conventionally done, the intensity of the emitted electron beam in the length direction of the cathode ( However, by applying a pulse voltage through a diode as in the present invention, an extremely uniform electron beam can be extracted by reducing the potential difference between both ends of the hot cathode to almost zero.

FIG. 6 shows experimental results regarding the density of the electron source shown in FIG. 3. Curves 40, 41 and 42 show the distribution of the electron beam flowing into the electrode 22 when the voltage applied to the cylindrical partition electrode 21 is changed. Curves 40, 41 and 42 are applied to electrode 21 -
It shows the distribution when 10V, -20 and -30V were applied. As can be easily understood from FIG.
As the voltage applied to 1 becomes more negative, the electron beam distribution becomes more concentrated in the center. This is because the equipotential surface within the cylindrical electrode 21 forms a hanging glass-like focused electric field (broken line) toward the center.

Therefore, the utilization rate of the electron beam emitted from the linear hot cathode can be significantly increased.

That is, 43 in FIG. 6 shows the distribution of the electron beam when the electrode 21 is not provided and the electron beam is extracted in the conventional manner. In this case, the electron beam flows over the entire surface of the electrode 22, so the cathode 2
Although only a small portion of the electron beam emitted from the electron beam can be used, as in the present invention, by providing the cylindrical electrode 21 and applying a negative potential, the electron beam distribution 40 shown in FIG. , 41, 42, etc.
Since the required minimum electron beam can be generated and the electron beam flows almost perpendicularly into the through hole 22a of the electrode 22, the electron beam can be focused well and the electron beam can be extremely convenient for improving the resolution. Obtainable.

Control Electrode Section The electron beam control electrode section is composed of an electrode plate 22 for extracting an electron beam, a group of strip-shaped electrode plates 23, and a grid-shaped electrode plate 24. The strip-shaped electrode plates 23 are each insulated and arranged at 1.27 mm intervals, 81 of which are arranged perpendicularly to the 15 linear hot cathodes 20. Each strip-shaped electrode plate 23
The grid electrode plate 24 has through holes 23a and 24 coaxially with the through hole 22a formed in the electrode plate 22.
A is drilled. The diameters of the through holes used were 0.8 mm and 0.6 mm. It is desirable that the interval between each electrode plate be as small as possible. Usually 0.3~
The spacing is kept at 0.5mm. Each strip-shaped electrode plate 23 is connected to an image signal circuit (see FIG. 7) so that image signals for one scanning line are sequentially applied. A bias voltage is applied to each strip-shaped electrode plate 23 to cut off the electron beam, and by applying a positive image signal to each strip-shaped source electrode plate 23, the amount of electron beam passing through is controlled. Control. A so-called electrode plate 23 performs a switching action. When applying an image signal to each strip-shaped electrode 23, the switching action and the focusing ability of the passing electron beam change depending on the potential of the adjacent electrode.
In order to prevent these interactions, it is necessary to reduce the distance between the three electrodes. According to the experimental results, it has been revealed that if the distance between the three electrodes 22, 23, and 24 is kept equal to or less than the distance between the through holes, the influence of the potential of the adjacent electrodes is negligibly small.

Electron Beam Focusing Section The grid electrode 25, which constitutes the electron beam focusing section with the grid electrodes 24 and 25, is almost the same as the grid electrode 24. The electron beam is collimated by the two electrodes or focused by a potential difference applied between the two electrodes. Furthermore, an Einzel lens system can be constructed by inserting another electrode plate (not shown) between both electrodes. In any case, in order to focus the electron beam to the required beam diameter on the display surface 30, it is necessary to
At the same time, it is necessary to appropriately select the voltages to be applied to each electrode of the cathode section and the electron beam control section. The energy of the electron beam incident on the next stage electron beam deflection electrode is determined by the voltage applied to the grid electrode plate 25, and the energy of the electron beam is determined depending on the vertical and horizontal deflection widths of the electron beam. It is necessary to apply a certain voltage.

Electron beam deflection section The electron beam deflection section includes 15 pairs of vertical deflection electrodes 26,
26', 81 pairs of horizontal deflection electrodes 27, 27', and a grid electrode 28. 15 pairs of vertical deflection electrodes are connected every other pair, and each 15 pairs are connected at the same time.
A 16-step staircase deflection voltage is applied. Similarly, the 81 pairs of horizontal deflection electrodes are also connected every other pair.
Three steps of staircase wave deflection voltages are simultaneously applied. Therefore, an image of 240×243 pixels can be obtained on the image display surface. As is easily understood, 15n×81m pixels can be obtained by applying n-stage and m-stage staircase wave deflection voltages to the vertical and horizontal deflection electrodes, respectively. The grid electrode 28 forms a pair with a metal back electrode 29 provided on the surface of the display panel 31 to constitute an electron beam accelerating electrode. 29 at the same time
serves to prevent the influence of the high electric field in the acceleration region from reaching the deflection electrodes so that the electron beams deflected by the deflection electrodes 26 and 27 flow into a predetermined position on the display panel surface. do. It is desirable that the grid electrode 28 has a high electron beam transmittance, but in order to eliminate distortion of the electron beam trajectory due to electric field distortion in the vicinity of the grid electrode 28, it is desirable that the hole diameter be 0.3 mm or less. In the device of the present invention, the linear hot cathode 20 can be deflected in the axial direction, that is, in the horizontal direction, without using the electrode 27.

With the above deflection electrode system, an image with uniform brightness can be obtained over the entire display surface by deflecting the image by ±2.54 mm in the vertical direction and ±0.635 mm in the horizontal direction.

When the voltages shown in Table 1 are applied to each electrode of the image display device described above, the electron beam current for one scanning line is 100 μA, the diameter of each beam is 0.2 mm, and the accelerating voltage
When scanning the entire surface at 10KV, a surface brightness of 150L was obtained.

Table 1 Vertical drive pulse voltage -13V Partition electrode plate 21 voltage -10V Beam extraction electrode 22 voltage 10V Horizontal drive pulse voltage 20 Focusing electrode 24 voltage 30V Focusing electrode 25 voltage 180V Vertical deflection voltage p-p150V Horizontal deflection voltage p-p70V Grid Voltage of the electrode 28: 200V Voltage of the accelerating electrode 29: 10KV Driving method The image display device of the present invention is most effective when used as a TV image display device.
An example in which this device is used as a TV image display device will be described below.

FIG. 7 shows a conceptual diagram of the drive system for TV image display according to this embodiment. This device has 15 vertical electron beam control electrodes (linear hot cathodes) and 81 horizontal electron beam control electrodes (strip electrodes). The display method is a one-scan line simultaneous display method generally practiced in matrix display devices. Further, as mentioned above, vertical and horizontal deflection electrodes are provided corresponding to the vertical and horizontal electron beam control electrodes.

In FIG. 7, a video signal input to a synchronization separation circuit 51 is input to a control signal processing circuit 52 and an image signal processing circuit 53. In the image signal processing circuit 53, the image signal for one horizontal scanning line is processed into 486 pixels.
The 1st, 7th, 13th..., 481st signal is stored in the storage device 54a, and the 2nd, 8th, 14th,...,
The 482nd signal is stored in the storage device 54b, ..., 6,
The 12th, 18th, . . . 486th signals are sequentially stored in the storage device 54f. The image signals stored in each storage device are sequentially transferred to the horizontal drive circuit 56 via the switching circuit 55 in synchronization with the signal from the control signal generation circuit 52, and the image signal voltage is applied to the 81 horizontal electron beam control electrodes 23. applied. At this time, if the scanning time of one horizontal scanning line is 63 .mu.s as in normal TV image display, the signal voltage from each storage device is sequentially applied for 10.5 .mu.s, which is 1/6 of one horizontal scanning time.

On the other hand, one of the signals sent from the control signal generation circuit 52 is input to the horizontal deflection drive circuit 57, and 81
A deflection voltage as shown in FIG. 8a is simultaneously applied to the pair of horizontal deflection electrodes 27. As a result, for example, the first 10.5 μs time is the maximum to the left toward the display board surface.
0.635mm, the next 10.5μs time is shifted to the right by 0.425mm, and the sixth 10.5μs time is shifted to the right maximum.
Apply a voltage that causes a deflection of 0.635 mm. Repeat the above operations in sequence. The timing of this deflection is performed in synchronization with the switching circuit 55.

Next, vertical scanning will be explained. In the case of normal TV image display, it is necessary to apply signal voltages sequentially from top to bottom every 63 μs. Assuming that the number of vertical scanning lines is 480, first, the first linear hot cathode 20 located at the top, for example, is scanned for 16.6 m for one frame.
A negative signal voltage of 1/15 of s, that is, approximately 1.1 ms, is applied via the vertical drive circuit 60, and in synchronization, the vertical deflection drive circuit 58 produces 16 gradations as shown in FIG. 8b. The vertical deflection voltage is applied to the vertical deflection electrode 26.
to be applied. For example, the first 63μs is 2.54 in the upward direction.
mm deflection, the next 63μs time is 2.202mm deflection, and then sequentially shift downward by 5.08/15mm, 16th 63μs
time, it is deflected downward by 2.54mm. Below in order 2
The same operation is repeated for the 3rd, 3rd, . . . , 15th linear hot cathodes to scan one field. Regarding the next field
By superimposing the bias voltage for 5.08/32 mm deflection on the vertical deflection signal voltage, it is possible to perform interlaced scanning and vertical scanning for warming one frame's worth of images.

As is clear from the above description, since the display device of the present invention can extract a uniform electron beam from the linear hot cathode, a clear image without unevenness can be obtained. Further, another image display device of the present invention using this as a flat panel image display device can obtain a high-resolution screen, and the number of electrodes can be significantly reduced compared to conventional ones, and therefore the driving speed is The circuit is simpler, cheaper, easier to implement, and the number of connection terminals is reduced, resulting in fewer failures.

[Brief explanation of the drawing]

FIG. 1 is a main schematic configuration diagram of a conventional flat panel display device, FIG. 2 is an exploded perspective view of the main components of a display device according to an embodiment of the present invention, and FIG. 3 is an electron source in the device of the present invention. FIG. 4 is a curve diagram showing changes in the electron beam current flowing through each electrode when pulse driving is performed in FIG. 3, and FIG. 6 is a diagram showing the distribution of the electron beam current of the electron source in the present invention, and FIG. 7 is a diagram showing the drive of the display device of the present invention when displaying on a TV. FIGS. 8a and 8b, which are conceptual circuit diagrams for explaining the system, are diagrams showing the waveforms and time relationships of the horizontal and vertical deflection voltages of the present invention. 20... Linear hot cathode, 21... Partition electrode, 22
... Electrode for extracting the electron beam, 22a,
23a, 24a...through hole, 23...rectangular electrode plate, 24...grid electrode plate, 26, 26'...vertical deflection electrode, 27, 27'...horizontal deflection electrode, 3
0... Fluorescent layer, 31... Glass plate, 32... Diode, 33... Negative pulse voltage generator, 57
... Horizontal deflection drive circuit, 58 ... Vertical deflection drive circuit, 59 ... Image display device.

Claims (1)

[Scope of Claims] 1. A plurality of linear hot cathodes, an electrode means for extracting an electron beam in which a through hole is provided along the axial direction of the hot cathode corresponding to each of the hot cathodes, and the hot cathode. Electron beam control electrode means comprising a plurality of electrodes having through holes substantially orthogonal to the through holes provided in the electrodes for extracting the electron beams, electrode means for deflecting the electron beams, and the electron beams. An image display device comprising an electrode means for accelerating the electron beam and a display means coated with a phosphor that emits light upon collision of the electron beam, and is housed in a glass container with at least a display surface transparent, A pulse signal generating means is connected to one end of the linear hot cathode, a power source for heating the linear hot cathode is connected to the other end via a diode, and the diode is biased in a reverse direction by the pulse signal generating means. A pulse signal voltage is applied to the linear hot cathode so that the electron beam is extracted from the linear hot cathode while the potential difference between both ends of the linear hot cathode is temporarily reduced to approximately zero. image display device. 2. When the quotient of the number of scanning lines on the display screen divided by the number of linear hot cathodes is m (m is an integer), a pulse signal voltage having a time width of m scanning lines is sequentially applied to n linear hot cathodes. The image display device according to claim 1, characterized in that the voltage is applied to the cathode. 3. When the quotient of the number of scanning lines on the display screen divided by the number of linear hot cathodes is m (m is an integer), a pulse signal voltage varying in m steps is applied to the n linear hot cathodes. 2. The image display device according to claim 1, wherein the pulse signal voltage is applied to the electrode means for deflecting the electron beam in synchronization with the pulse signal voltage. 4. A plurality of linear hot cathodes, partition means for partitioning the linear hot cathodes from each other, and an electron beam provided with through holes along the axial direction of the hot cathodes corresponding to each of the hot cathodes. an electrode means for taking out the electron beam, an electron beam control electrode means consisting of a plurality of electrodes having through holes substantially perpendicular to the hot cathode and corresponding to the through holes provided in the electrode for taking out the electron beam;
It has electrode means for deflecting the electron beam, electrode means for accelerating the electron beam, and display means coated with a phosphor that emits light upon collision of the electron beam, and at least a display surface is transparent. An image display device housed in a glass container, in which a pulse signal generating means is connected to one end of the linear hot cathode, and a power source for heating the linear hot cathode is connected to the other end via a diode. Then, a pulse signal voltage is applied to the linear hot cathode by the pulse signal generating means so that the diode is biased in a reverse direction, and the potential difference between both ends of the linear hot cathode is temporarily reduced to approximately zero. An image display device characterized in that an electron beam is extracted from the linear hot cathode. 5 When the quotient obtained by dividing the number of scanning lines on the display screen by the number of linear hot cathodes is m (m is an integer), a pulse signal voltage having a time width of m scanning lines is sequentially applied to n linear hot cathodes. The image display device according to claim 4, characterized in that the voltage is applied to the cathode. 6. When the quotient of the number of scanning lines on the display screen divided by the number of linear hot cathodes is m (m is an integer), apply a pulse signal voltage that changes in m steps to the n linear hot cathodes. 5. The image display device according to claim 4, wherein the pulse signal voltage is applied to the electrode means for deflecting the electron beam in synchronization with the pulse signal voltage.