|Publication number||US3041496 A|
|Publication date||Jun 26, 1962|
|Filing date||Nov 19, 1958|
|Priority date||Nov 19, 1958|
|Publication number||US 3041496 A, US 3041496A, US-A-3041496, US3041496 A, US3041496A|
|Inventors||Hopengarten Abram, Jr Edgar M Creamer|
|Original Assignee||Philco Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (3), Classifications (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
E. MQ CREAMER, JR.; ETAL 3,041,496
June 26, 1962 TELEVISION RECEIVERS Filed Nov. 19, 1958 g Sheets-Sheet 1 E. M. CREAMER, JR., ET AL TELEVISION RECEIVERS Filed Nov. 19, 1958v 2 Sheeizs-Sheerl 2 States Unite This invention provides what is believed to be a new type of television receiver, to wit: a truly portable, selfcontained, battery-operated, long-playing receiver unit. The new unit will operate `at any desired location, regardless whether power outlets be available. It is able, pursuant to charging or replacing of battery elements, to receive extended broadcasts and to convert them into bright and sharp pictures. The industry has long endeavored to provide a television receiver, capable of such service, and it is believed that the invention has made it available for the rst time.
Although a number of mechanical, electrical and optical features have been combined in achieving this result, the following has been found to be of special importance. The new device comprises not only miniaturized, low power circuit components, combined with high magnification optics; it is more essentially characterized by the use of a peculiarly shaped, dimensioned and constructed picture tube unit, arranged `for especially acute-angled cathode ray deection and desirably short beam length. This deflection is advantageously obtained by means comprising a particular yoke or deflection system of electromagnetic type.
As `a further and more particular feature said electromagnetic deflection system forms part of the power source for the receiver and employs a novel combination of structural and operative characteristics. In any event the new arrangement minimizes bulk and weight, not only of the cathode ray tube itself but of a m-ajor cooperating unit, the batteries of the set; and preferably, it is so arranged as to minimize also the bulk of the power transformer means. By such expedients, unparallelled savings of over-all bulk and weight of the receiver have been achieved, thereby allowing the desirable type of service as outlined.
In a receiver constructed according to the present invention the cathode ray tube desirably has a bulk, as well as a yoke, which can be made short, as well as narrow, in comparison with a dimensional standard such as that furnished by the, electrodes of the tube. Preferably, the yoke and tube unit forms an approximately cylindrical body which is only about three times as long as the electrode assembly preceding the yoke; 4and while such ya tube is rather small, by itself, the indicated smallness and construction of the tube has made it possible to minimize dimensions and bulk of the associated battery unit to an even more remarkable extent. Hitherto the battery for a miniature picture tube, if relied upon for energizing the receiver during a number of hours, represented a package of incomparably larger size than the tube itself. The size of such package has now been reduced to the point where it need only have about the same form, length and ldiameter as are employed for the miniature tube. y
In a preferred embodiment of the new receiver set, a major portion yof the overall space provided is filled by elongate battery cells, mounted in positions parallel and symmetrical with, adjacent to and about coextensive with the cathode ray tube. Relatively minor space in the receiver cabinet is occupied by circuitry components and panels. The so-arranged unit is further provided with auxiliary parts, including an 'optical magnifying system superimposed over the screen of said cathode tube. The
'i atent ice magnifying system is desirably formed of rectangular reilector means arranged transversely of the axis of the tube.
Of course the industry has long been in possession of many or all of the elements forming part of the new subcomb-inations or overall combination hereof, including various cathode ray deflection means, as well as low power cathode systems, transistor type amplifiers, high capacity batteries, and high magnification optics. It is however believed that the present inventors are the first to realize a particularly large, signicant and hitherto unanticipated saving in overall bulk and weight of a battery-operated television receiver, by combining a special tube, as outlined, with the required auxiliary receiver means.
In the development of this new combination the following requirements, among others had to be strictly complied with: The tube and the complete electrical system must be of such design that full capacity operation thereof can be had by battery power for a period of several hours; nevertheless the battery together with the receiver set, optical magnifier and auxiliary parts must be light enough to be carried conveniently by one person, even by a child. The electron beam and phosphor screen must provide high resolution and brilliance of televised pictures, however said beam and the auxiliary circuitry for the same, as mentioned, must be capable of being operated with an absolute minimum `of power. Optical magnification of the picture provided by the small tube must be such that an image of convenient size can be viewed by the user, or by several users, stationed at a distance from the set; nevertheless the magnifying system, as well as the other parts of the device, must be as small and light as possible. Also, the complete unit must be mechanically, optically and electrically arranged so that it can be carried about with complete freedom and readily started in operation, while a variety of auxiliary means should be provided, including for instance means to prevent outdoor light from interfering with the viewing of the picture.
The problems involved in each of these objects, as well as the various coniiicts between the several objects, have been overcome by the present invention. Additionally, most if not all of the advantageous adjustments and other features provided by standard TV receivers of modern design have been utilized in a preferred embodiment of the invention, which will now be described in detail.
In the drawing, FIGURE l is a vertical section of said embodiment; FIGURE l-A is a schematic longitudinal section of the tube sub-assembly form-ing part of said embodiments; FIGURE 2 is a perspective view of the apparatus showing it adjusted forI carrying', and FIGURE 3 is a similar view of the apparatus in process of being adjusted for operation. FIGURE 4 is a diagram of the optical system; FIGURE 5 is a ldiagram of the mechanical structure; and FIGURE 6 is -a block diagram of the electrical system used in the new receiver.
As shown in FIGURE 1 the receiver cabinet lll contains a cathode ray tube 11, of narrow, acute deflection angle 12, such as 30 or less. The tube accordingly has a bulb 13 of limited width. This bulb is short as well as narrow, so that phosphor screen 14 at one end thereof is very small. The screen may for instance provide a net picture area of about 1% times 1% inches, such specilic dimensions Abeing stated, of course, for illustration only.
Between bulb 13 and neck 1S at the opposite end of tube 11, which contains a suitable electrode assembly, -coils 16 and 17 are interposed to provide a magnetic yoke for deflection of the cathode ray beam generated, focused and controlled by said assembly. For reasons to be explained hereinafter, horizontal deflection coils 16 are advantageously disposed on the outside of vertical aesinet;
deflection coils 17. Yoke 16, 17 is about as long as neck 15, Whereas bulb 13 is shorter, not, as usual, longer than the yoke. The bulb is approximately as wide as the yoke, both being advantageously of approximately cylindrical shape.
The dimensional features of tube 11 are additionally illustrated in FIGURE l-A, wherein the length of neck 15 is indicated at In while the length of the yoke is indicated at ly and that of the bulb at lb. A certain length ln of neck 15 is basically required, as a certain region of space must be occupied by heater filament F, cathode C, control grid CG and focusing electrode FE, some or all of which must be disposed on one side of yoke 16, 17 when bulb 13 with screen 14 is disposed on the other side. The space requirements of electrode structure C, FE, etc. will be appreciated more fully when it is remembered that on the one hand the tube must also contain an anode coating or lining AC which starts in bulb 13 and extends almost along the entire length of the tube and into the area of focusing electrode FE, and that on the other hand the anode region so provided must be spaced sulliciently from other electrodes, such as control grid CG, to avoid sparking between such electrodes. Thus it will be seen that a tube neck 15, or an electrode assembly such as FE, CG, C and/or F, generally has an irreducible length In, amounting for instance to at least about an inch or two, and which in turn can be used as a standard of comparison for other dimensions such as ly and lb.
In many tubes dimension Iy, the length of the yoke structure, is considerably greater than said basic length In, as it is usual to take advantage of the fact that, when a given electron velocity has been generated by the electron gun, deflection of such electrons is proportional to the length of the dellecting field, aside from the inuence of factors such as the ampere turns of the deecting coils. In the present receiver, however, it has been found possible, and to a large extent desirable, to minimize such length and also such other factors, as will be explained hereinafter. Particularly yoke length ly can be of an order of magnitude similar to the length ln of neck 15 (see FIGURES l-A and l).
Contact pins 18 at the end of neck *15 are shown as being plugged into socket 19, suitably secured to a bottom panel 20 in cabinet 10. The opposite or upper end of tube 1'1 is shown as being held in a retainer ring 21, suitably secured to upper horizontal panel 22 of the cabinet, so as to expose screen 14. The mounting of socket 19 and/or ring 21 can be made adjustable by mechanical features not shown.
Above screen 14, cabinet 10 has a magnifier compartment 23, wherein a precision-ground, plane-parallel glass plate 24 is mounted in an inclined position, extending across and at 45 to the axis of the tube; said glass plate having a at semi-reflecting surface 25 which also faces the concave surface of a curved mirror 26. The user, facing Vthe curved mirror through the semi-reflecting plate, sees the televised picture as a virtual image 14 of screen 14, behind the mirror, as indicated in FIGURE 4.
As best shown in FIGURE 2, cabinet 10 has a handle for carrying the entire unit in one hand, said handle being provided by a pair of rod structures 31, 32 which converge upwardly from connecting structures 33 secured to cabinet side wall 34. As further shown in FIGURE 3, these rod structures 31, 32 can also be re-arranged for use as a stand for the cabinet, making the unit adjustable so that the televised pictures can be seen to best advantage. For this purpose the cabinet is tiltably suspended on pivot means 35, disposed between connecting structures 33 and side walls 34. When a suitable angle of upward or downward tilt of the cabinet, on stand 311, 32, has been determined by the user, so as to provide full and convenient viewing of the pictures, the user can fix the corresponding orientation of the cabinet, including front aperture 36 of magnifier compartment 23,
for instance by lock-nut means forming part of pivot means 35.
As further shown in FIGURE 3, magnifier compartment 23 can be in effect be extended toward the user, in order to minimize the entering of stray light and thus to preserve maximum contrast of the virtual screen image, even when operating in daylight. This is achieved by a visor 37, swingably secured to the top of compartment 23 and combined with marginal side aps 38, which flaps may be slidably disposed adjacent the inside surfaces of cabinet side walls 34.
The receiver has a selector 39 and ne tuner 40, as well as knobs 41 to 46 (FIGURES 2 and 3), for horizontal and vertical hold control, sound control and related operations, as is usual in TV receivers. It is equipped with retractable and extendable antennas 47, 48. The front of cabinet 10 has grillwork 49 incorporated therein. As shown in FIGURE 5, baffle means 50 is provided, behind said grillwork, for the mounting of loudspeaker and/or earphone jack means, not shown, which may be of such types as are used in portable radios.
If reference will now be made to FIGURE 4, it will be seen that light from screen `14 of cathode ray tube 11 is first reflected by semi-reflector 24, 25 toward curved mirror 26, which then reflects the light toward viewing region VR. The curvature of mirror 26 is desirably slight and it can then be spherical, without any serious aberration of the light. The semi-reflective coating of plate 24 is advantageously of the type providing about seventy percent reflection. The entire optical system 24, 25, 26 is so arranged that the several light beams emanating from each point of the screen, some of which diverge widely as illustrated by lines a and a', result in similarly divergent `beams b, b incident on the curved mirror. This mirror forms divergent beams, two of which are shown at c, c', and which have convergent continuations, such as are shown at d, d and e, e', behind the spherical mirror, thereby forming a substantially magnified, remotely viewable, virtual image 14 of screen 14.
The optical system 24, 26 preferably is of such arrangement and size and mainly of such width as to provide a viewing region VR, having some appreciable size and wherefrom the entire virtual image `14 can be seen,
said region VR being spaced from cabinet 1() by an adequate distance by means of said slight curvature of mirror 26. It is also preferred that spherical mirror 26 be relatively wide, see FIGURE 5, thereby making viewing region VR correspondingly wide, although the height of said region-shown in FIGURE 4-can well be limited.
The structural framework of cabinet 10, as shown in FIGURE 5 includes corner structures 51, 52, 53, etc. which support, on the outside thereof, suitably finished covering sheets 54 of leather, plastic or the like. Within the cabinet, a panel and partition structure is shown which includes, in addition to the aforementioned lower and upper panels 20, 22, a series of vertical circuit panels such as side panels 55, 56, back panel 57 and, between the side panels and parallel thereto, a partition and reinforcement panel 58. Adequate panel area is thus provided for numerous miniature circuit components 59, 60, etc.; and the panels may also cooperate with frame elements 51, etc. in providing a portable cabinet structure of sufficient strength and rigidity.
The outer circuit panels, such as side panels 55, 56, have circuit components mounted on their surfaces facing toward the inside of cabinet 10, while having soldered conductor patterns 61 exposed ltoward the outside of the cabinet yand the inside of decorative covering 54. Marginal securement of panels 55, 56, etc. on metal structures 51, etc. is provided by a groove and key arrangement 62, whereas corner joints between panels normal to one another, for instance between bottom and reinforcement panels 20, 58, is achieved by interlocking notches 63 in the panels, as is well known in the construction of other containers.
Although the required battery capacity, as repeatedly mentioned hereinabove, has been greatly reduced by the present invention, volume and weight `are still chargeable in great part to battery structure, as the unit is normally expected to televise extended programs, be- :tween battery recharging or replacing operations. Thus it will be seen that battery cells 64, 65 are likely to be at least about as large as is the basically required tube |11. It has been found most eiiicient to arrange said cells in form of cylindrical units parallel and close to said tube and about as long as the same. Both the carrying of the unit (FIGURE 2) and the operative positioning thereof (FIGURE 3) are further facilitated by arranging these cells in later-al symmetry -about the cathode ray tube (FIGURE 5); said tube being desirably installed centrally with respect to the width of the cabinet and as a vertically oriented component for optical reasons. The parallel-symmetrical arrangement of major components 1111, 64, 65 contributes also toward the possibility of making the structural framework 51, 52, 53 relatively light. It is preferred that the batteries be of the nickel-cadmium type, whereby they can be made relatively light, while providing the possibility of convenient recharging, and other known advantages. The shape and size of the two batteries desirably resemble that of dry cells for portable ashlights of the well known, d0- mestic type.
p Cabinet contains the aforementioned, small, upper or optical magnifying chamber 23,- which necessarily is free or at least substantially free of structures which would interfere with the passage of light. Below this chamber, cabinet 10 provides an underlying electronic circuitry compartment 67, the size of which is comparable to that of upper chamber 23 although it may be narrower and longer, as shown. This lower chamber, accordingly, contains not only (l) the picture tube 11 and (2) the complete set of other receiver circuit components 59, 60, including the mechanisms required lfor adjusting elements 46, v45, etc., but also and importantly (3) the complete electrical power storage and supply structure 64, 65 ttor extended operation. These major groups of components (l) to (3) account for the entire space of the circuitry compartment. Storage unit (3), as mentioned, provides forY extended periods of operation; in the illustrated unit it is operable for -at least four to tive hours, providing pictures of high brilliance and sound output of considerable power.
Although the volume of the combined battery units 64, 65 has been kept to the same approximate order of magnitude as the size of the basically required cathode ray tube 11, the weight of said battery units, as will readily be understood, is still appreciable. It is likely to be greater than that of any other major group of elements forming part of Ythe presen-t combination. Heretofore, however, batteries had to be incomparably larger and heavier yet, whenever it was desired to make a television receiver portable, beyond the direct vicinity of house service outlets or `the like, and yet to operate it for a number of hours. In typical cases it was necessary to provide a battery cabinet, separate from and at least as large as the remaining receiver apparatus and several times as heavy as the same, which had to provide an output of 100 watts, or more, for the required number of hours. The new battery unit, by contrast, forms a relatively small part of the receiver. It need not provide more than the power of about a half dozen flashlight batteries, of the type already mentioned, to allow receiver operation of the same duration as indicated, with viewable pictures of equal (virtual) size and of fully equal quality.
The reason why it was possible, according to this invention, so drastically to reduce the power requirements can best be explained in connection with FIGURE 6. Batteries 64, 65 are here shown connected to cathode ray tube l11 and loud-speaker or earphone system LS, EP, through basically normal television circuitry, represented by conventional block symbols. Such symbols lindicate for instance the audio circuits A and video circuits VI; it is believed that details of such circuits need not be shown herein. The battery has one terminal grounded and the other at --6 volt. It is shown as provided with battery charging system BC having a socket or plug for connection of a power cord; but no such connection, as mentioned, is required during the normal operation of the receiver.
The power transformer unit PT is provided with terminals for relatively low voltages such as -12 volts and +12 volts and with terminals `for positive voltages of much higher orders of magnitude, such as +300 volts and +9000 volts. 1
It has not been usual thus Ifar, at least in the analysis of portable receiver circuitry, to analyze the operation of television circuit branches, such as circuits LS, A, VI, etc. with respect to the question of which are the major areas of energy dissipation, and which of the power source terminals, of diiferent voltage, supply the greatest amounts of po'wer. Such analysis, however, has been found important for purposes of this invention. A general statement and explanation of such an analysis has therefore been facilitated by the use, in FIGURE 6, of relatively heavy lines wherever energy dissipation is relatively heavy, and of -thinner lines in all other cases. It must be realized, however, that such distinction of regions of light and heavy power consumption represents only a iirst approach to the problems which have been solved by the invention.
Considering the various circuit lines in greater detail, it will be seen that heavy consumption of power is involved, in iirst place, along the -6 volt line 101, 102 through the filament F of the receiver cathode, grounded at 103.
In the next place, and importantly, significant power ows also through the further -6 volt line 101, 104 leading to and through the horizontal deiiector circuits H. 'Ihe amperage continuously required along this latter line is selectable, within wide limits, depending very largely on the angularity of deflection. The demand is high when deflection is wide, while being very much lower when deection is narrow. 'In fact, the reduction of this latter demand is greatly in excess of direct proportionality to the angularity of beam deflection. It is for this latter reason that a special cathode ray tube design, characterized primarily by the use of narrow deilection, is required according to this invention. Even a slight increase of deflection angle 12 (FIGURE l) would lead to enormous increase of total volume and weight of required batteries 64, 65, unless the capacity of the receiver unit, in terms of operating time between recharging periods, be reduced to the point where complete programs can no longer be received.
Wattage requirements are also variable with deiiection angles insofar as line of vertical deflection circuit V is concerned; however, the absolute amount of energy dissipation, in this vertical system, is relatively insignificant, as much lower frequencies and usually smaller total deections are involved. A relatively light demand is accordingly indicated by the use of a thin line 105, in contrast with the heavy line 104 to the horizontal deflection circuit H. i
The horizontal deflection coils 16, as should be noted in the next place, are also employed, in conjunction with power transformer PT, for generation and conversion of auxiliary voltage supplies, which are shown as +9000 (high voltage), +300, +12 and -12 volt supplies. For this purpose, current from the -6 volt battery terminal is caused to flow through a circuit 106 which includes power transformer PT and horizontal yoke coils 16. This basically known arrangement utilizes coils 16 not only as beam dellectors but also as means for energy storage for beam generation etc. This double function of coil 16 is particularly desirable in a small, portable unit, such as the present one.
However, it Ymust now be noted that, when and as the scanning or deflecting angle is small, the total circulating power in the deflection coil is not large enough to enable efficient conversion and generation of said auxiliary supplies. Therefore, an additional storage coil is used, which takes the form of the primary inductanpe of power transformer PT. The total energy to be stored for power generation is greater than the energy required for beam deflection in either inner or outer deflection coils. Therefore the outer deflection coils, being the less efficient as dellectors, were chosen as combined storage and horizontal deflection coils, thus enabling among other things a saving in power for the vertical (inner) deflection, and reducing the total power required to a minimum. COnventional or hitherto proposed apparatus would not allow such operation.
The energy stored in coil 16 and transformer PT, as described, is utilized largely for high voltage generation, the high voltage in turn being used in a circuit which includes the +9000 volt terminal, line 107, screen anode AC, the electron beam, the picture tube cathode C and cathode return circuit CR. As the brightness of screen 14 must be relatively high, this circuit represents substantial wattage, especially in view of the great reduction of wattage in circuits 101 to 106.
It is of course understood that at least under some circumstances, relatively high dissipation of energy may take place along line 108 to audio circuits A and loud-speaker-earphone system LS, EP, as indicated by the use of a heavy, broken line superimposed on a thin line. Much smaller, at least in normal operation, is the power consumption involved in the video circuits Vl, that is, the circuits fed by -l-12 volt line 109, -6 volt line 110, and -12 volt line 111.
Similarly insignificant powei is consumed in sync block S and its supply line 112, starting at the -6 volt battery terminal. As already mentioned, all or at least most of the active circuit elements, in the video and sync circuits, desirably are semiconductor units or transistors 68 (FIGURE 5); thus we eliminate all requirements of filament heating, except iu the cathode ray tube, where filament F is required for heating purposes. The total power carried by control circuits 109 to 112 is therefore likely to be less than that carried by any one of circuits 104 to 106 for deflector coils 16, 17; this applies even upon the significant reduction of the latter amount of power which has been discussed. Similarly small is the power consumed in the RF and IF stages of the overall circuit, involving electronic analysis of the signal received from the antenna, such as the radio frequency stage RF, the mixer stage M with local oscillator LO, the intermediate frequency stage IF and the detector stage D; said stages being supplied with power by +12 volt lines 113, 114, 115 and 116, respectively. No significant power at all is consumed by circuit 117 leading from the +300 volt terminal to the focusing electrode FE of cathode ray tube 11.
Thus it will be seen that the amount of energy required for operating the new unit, and the corresponding size of power source 64, 65, PT, as well as of tubes 11, have been reduced to such a low level as to make a self-contained, freely portable, long-playing television receiver practical.
Enlargement of the deflection angle (with or without enlargement of the beam length and with or without use of an optical magnifying system) would in effect lead to such a prohibitive increase in battery requirements as to make it unattractive, and in most cases impossible, either to carry or satisfactorily to operate the resulting receiver unit. Therefore, although a great many variations are possible in the electrical, mechanical and optical arrangements employed, most of these arrangements are of secondary significance for purposes of this invention, compared with the narrow-angled beam deflection and correspondingly compact arrangement of tube and power source structures.
While only a single embodiment of the invention has been described, it should be understood that the details thereof are not to be construed as limitative of the invention, except insofar as is consistent with the scope of the following claim.
In a television receiver wherein a power source supplies electric deflection power to electromagnetic circuits for horizontal and vertical deflection of a cathode ray beam, said circuit for horizontal deflection being associated with said power source to derive high Voltage energy from such deflection power for application of said energy to a high voltage electrode, the improvement which comprises: a vertical deflection coil forming part of said circuit for vertical deflection; a horizontal deflection coil forming part of said circuit for horizontal deflection and disposed outside of said vertical deflection coil; and a cathode ray tube having a neck surrounded by said coils and having a bulb the width and length of which is not appreciably greater than the outer diameter of said horizontal deflection coil, said coils 4being adapted to deflect said cathode ray beam with an acute deflection angle corresponding to said width and length of said bulb.
References Cited in the file of this patent UNITED STATES PATENTS 1,981,322 Nakajima Nov. 20, 1934 2,165,078 Toulon July 4, 1939 2,457,773 Cawein Dec. 28, 1948 2,509,508 Kalff May 30, 1950 2,781,475 Fyler Feb. 12, 1957 2,830,230 Fyler Apr. 8, 1958 2,939,978 Irvine lune 7, 1960 FOREIGN PATENTS 18,564/34 Australia Feb. 20, 1936 344,884 Italy Nov. 30, 1936 OTHER REFERENCES 1958 IRE Wescon Convention Record, Part 7, August 19-22, 1958, page 57.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1981322 *||Nov 16, 1932||Nov 20, 1934||Kenjiro Takayanagi||Cathode ray tube|
|US2165078 *||Nov 6, 1936||Jul 4, 1939||Rca Corp||Television receiving set|
|US2457773 *||May 24, 1944||Dec 28, 1948||Farnsworth Res Corp||Deflecting coil|
|US2509508 *||Oct 19, 1946||May 30, 1950||Hartford Nat Bank & Trust Co||Cabinet structure for television receivers|
|US2781475 *||Apr 1, 1954||Feb 12, 1957||Motorola Inc||Television receiver|
|US2830230 *||Jun 16, 1955||Apr 8, 1958||Motorola Inc||Television receiver|
|US2939978 *||Oct 16, 1957||Jun 7, 1960||Canadian Admiral Corp Ltd||Deflection yoke|
|AU1856434A *||Title not available|
|IT344884B *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3536832 *||May 2, 1966||Oct 27, 1970||Erich Zipse||Accessory apparatus for conversion of a screen picture into a three-dimensional virtual image|
|US4385316 *||Dec 17, 1980||May 24, 1983||Sony Corporation||Image projection system|
|US4991024 *||May 12, 1986||Feb 5, 1991||Hitachi, Ltd.||CRT display device|
|U.S. Classification||315/393, 348/E05.143, 348/783, 313/478|