Electronic blackboard and accessories such as writing tools

• US RE35,329 E
• Filed: 06/10/1993
• Issued: 09/17/1996
• Est. Priority Date: 06/22/1988
• Status: Expired due to Term

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Tanaka, Takeshi, Aoki, Kazuo, Murakami, Azuma, Senda, Toshiaki, Chikami, Toshihide, Funahashi, Takahiko, Yamanami, Tsuguya, Tomofuji, Yoshiaki, Inashima, Satoshi
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): LOOMIS, PAUL A
• Application Number:
  US08/074,569
• Time in Patent Office: 1,195 Days
• Field of Search: 178/18, 178/19, 345/157, 345/179, 345/173, 341/5
• US Class Current: 178/18.07
• CPC Class Codes: G06F 3/033 Pointing devices displaced or positioned by the user , e.g. mice, trackballs, pens or joysticks; Accessories therefor digitisers characterised by the transducing means G06F3/041
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/046 by electromagnetic means

Abstract

A characteristic and the position of an implement with a tuned circuit having one of plural resonant frequencies are determined. AC energy at the plural different resonant frequencies is supplied to a two-coordinate direction coil arrangement of a position sensing tablet. The tuned circuit changes the current flowing in the coil arrangement at the implement resonant frequency. The current change is used to signal the implement position and characteristic. The implement may be an eraser for supplying a signal to an electronic display and for removing a mark from a surface of a visual display overlaying the tablet of the eraser. A housing includes a surface for erasing the marking and two tuned circuits each having a reactance positioned close to opposite edges of the erasing surface. Two switches, when activated, cause the tuned circuits to have different resonant frequencies. The switches are respectively activated when opposite eraser edges are being pushed against the display surface. The implement may also be one of a plurality of markers, each for a different color. Another display responds to the signals to display the position and colors of the markings and selectively remove markings from areas corresponding to the eraser position.

Claims

1. An electronic blackboard apparatus comprising:

a writing surface,

a tool for modifying an image on the surface including a tuned circuit having a predetermined resonant frequency;

means for sensing the presence of the tool relative to said surface, said means including electric wave generating means for generating an electric wave with plural frequencies, one of which is resonant to said frequency, and an electric wave detection means for detecting an electric wave reflected by said tuned circuit;

said sensing means including coordinate detection means responsive to the electric wave reflected from said tool and generated by said generating means for detecting a coordinate corresponding to the position of said tool; and

image information processing means for processing, on the basis of the thus-detected coordinate, image information corresponding to an image formed by the tool on the surface.

2. An electronic blackboard apparatus according to claim 1, wherein said electric wave generating means and said electric wave detection means are arranged to be alternately operated.

3. An electronic blackboard apparatus according to claim 1 or 2, wherein said electric wave generating means and said electric wave detection means include x and y-direction loop coil groups.

4. An electronic blackboard apparatus according to claim 1 or 2 further wherein a plurality of said tools are provided, each of said tools having a tuned circuit with a different resonant frequency, equal to frequencies of the plural frequencies of the generated electric waves;

the coordinate detection means detecting the different resonant frequencies;

writing tool identification means for generating identification information expressing, on the basis of the detected frequency a characteristic of said tool which is being used on said sensing portion; and

image information processing means for processing image information which corresponds to the image on said writing surface on the basis of the detected coordinates of said tool and

identification information expressing the characteristic of said tool which is being used.

5. An electronic blackboard apparatus according to claim 1 or 2 wherein:

a pair of said writing surfaces are disposed on opposite sides of said means for sensing, said writing surfaces being capable of being used repeatedly;

means for detecting the surface which is being used for detecting the writing surface which is being used; and

coordinate conversion means for deriving indications in two coordinate directions of said tool as derived from said coordinate detection means.

6. The apparatus of claim 5 wherein the two coordinate directions are in the x and y directions.

7. The apparatus of claim 5 wherein the coordinate conversion means derives the indications intact.

8. The apparatus of claim 5 wherein the coordinate conversion means derives the indications intact after the coordinates have been converted on the basis of the writing surface which is being used.

85. An electronic blackboard apparatus according to claim 4 wherein:

a pair of said writing surfaces are disposed on opposite sides of said means for sensing, said writing surfaces being capable of being used repeatedly;

means for detecting the surface which is being used for detecting the writing surface which is being used; and

coordinate conversion means for deriving indications in two coordinate directions of said tool as derived from said coordinate detection means. .Iadd.

9. In combination, a position sensing tablet;

a two coordinate, direction coil arrangement associated with the tablet;

a tool means adapted to be moved relative to the tablet and coil arrangement, the tool means including tuned circuits having first and second resonant frequencies;

means for supplying AC energy at the first and second resonant frequencies to the coil arrangement;

the tuned circuits on the tool means when the tool means is placed in proximity to the tablet and coil arrangement respectively causing changes in currents flowing in the coil arrangement of said first and second frequencies; and

means for sensing the changes in the current flowing in the coil arrangement at said first and second frequencies and responding to the current changes at said first and second frequencies for deriving a signal indicative of coordinates of the tool means relative to the tablet and coil means.

10. The combination of claim 9 wherein the energy at the different frequencies is sequentially supplied to different coils of the coil arrangement.

11. The combination of claim 10 wherein the change is detected by supplying each of the coils during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to each of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one predetermined frequency.

12. The combination of claim 9 wherein said tool means is cordless and no electric power supply is connected to the tuned circuits thereof.

13. The combination of claim 9 wherein the signal is further indicative of first and second characteristics of the tool means respectively associated with the first and second frequencies.

14. In combination, a position sensing tablet;

a two coordinate, direction coil arrangement associated with the tablet;

a two coordinate direction display superposed with the tablet;

a marker for the display;

an eraser for the display;

the marker including a tuned circuit having a first resonant frequency;

the eraser including a tuned circuit having a second resonant frequency;

means for supplying AC energy at the first and second resonant frequencies to the coil arrangement;

the tuned circuits on the marker and the eraser when the marker is placed in proximity to the tablet and coil arrangement respectively causing changes in currents flowing in the coil arrangement of said first and second frequencies; and

means for sensing the changes in the current flowing in the coil arrangement at said first and second frequencies and responding to the current changes at said first and second frequencies for denying a signal indicative of the position of marking by the marker on the display as modified by the eraser.

15. The combination of claim 14 wherein the energy at the different frequencies is sequentially supplied to different coils of the coils arrangement.

16. The combination of claim 15 wherein the change is detected by supplying each of the coils during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to each of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one predetermined frequency.

17. The combination of claim 16 further including another two coordinate display responsive to the signal indicative of the position of the modified markings for displaying the modified markings.

18. The combination of claim 17 further including a plurality of said markers, each of said markers being for a different color and including a tuned circuit with a different resonant frequency, the means for supplying feeding AC energy at each of the resonant frequencies to the coil, the means for sensing responding to change sin the current flowing in said coil at each of the resonant frequencies, said another display displaying the position and colors of markings made by each of said markers.

19. The combination of claim 16 wherein the means for supplying supplies different frequencies in sequence to the coil arrangement such that in response to the marker having the first resonant frequency being proximate to and not being proximate the tablet the means for supplying respectively derives said first resonant frequency for first and second durations prior to deriving a second frequency, said first duration being considerably in excess of said second duration.

20. The combination of claim 19 wherein each of the first durations is divided into a plurality of said first and second intervals.

21. The combination of claim 14 further including another two coordinate display responsive to the signal indicative of the position of the modified markings for displaying the modified markings.

22. The combination of claim 21 further including a plurality of said markers, each of said markers being for a different color and including a tuned circuit with a different resonant frequency, the means for supplying feeding AC energy at each of the resonant frequencies to the coil, the means for sensing responding to changes in the current flowing in said coil at each of the resonant frequencies, said another display displaying the position and colors of markings made by each of said markers.

23. The combination of claim 14, wherein said marker and eraser are cordless and no electric power supply is connected to the tuned circuits thereof.

24. In combination, a position sensing tablet;

a two coordinate direction coil arrangement associated with the tablet;

multiple implements for movement relative to the tablet, each of said implements having a different characteristic associated therewith and including a tuned circuit having a different resonant frequency;

means for supplying AC energy at the different resonant frequencies to the coil arrangement;

the tuned circuits on the implements when the implements are placed in proximity to the tablet and coil arrangement causing changes in the currents flowing in the coil arrangement at said different frequencies; and

means for sensing changes in current flowing in the coil arrangement at said different frequencies and responsive to the current changes at said frequencies for deriving a signal indicative of the position and characteristics of the implements relative to the tablet.

25. The combination of claim 24 wherein the energy at the different frequencies is sequentially supplied to coils of the coil arrangement.

26. The combination of claim 25 wherein the change is detected by supplying each of the coils during a first interval with the AC energy at one of the different frequencies, the means for sensing being activated to be responsive to energy coupled back to each of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one frequency.

27. The combination of claim 26 wherein the means for supplying supplies different frequencies in sequence to the coil arrangement such that in response to an implement having a first resonant frequency being proximate to and not being proximate to the tablet the means for supplying respectively derives said first resonant frequency for first and second durations prior to deriving a second frequency, said first duration being considerably in excess of said second duration.

28. The combination of claim 27 wherein each of the first durations is divided into a plurality of said first and second intervals.

29. Apparatus for identifying a characteristic and position of an implement having one of plural characteristics, the implement including a tuned circuit having one of plural different resonant frequencies, comprising a position sensing tablet;

a two coordinate direction coil arrangement associated with the tablet;

means for supplying AC energy at the plural different resonant frequencies to the coil arrangement;

the tuned circuit on the implement when placed in proximity to the tablet and coil arrangement causing changes in current flowing in the coil arrangement at said one frequency;

means for sensing changes in the current flowing in the coil arrangement at said different frequencies and responsive to the current changes at said frequencies for deriving a signal indicative of the position and characteristic of the implement on the tablet.

30. The combination of claim 29 wherein the energy at the different frequencies is sequentially supplied to coils of the coil arrangement.

31. The combination of claim 30 wherein the change is detected by supplying each of the coils during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to each of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one predetermined frequency.

32. The combination of claim 31 wherein the means for supplying supplies different frequencies in sequence to the coil arrangement such that in response to an implement having a first resonant frequency being proximate to and not being proximate the tablet the means for supplying respectively derives said first resonant frequency for first and second durations prior to deriving a second frequency, said first duration being considerably in excess of said second duration.

33. The combination of claim 32 wherein each of the first durations is divided into a plurality of said first and second intervals.

34. The apparatus of claim 29 further including a two-coordinate direction display superposed with the tablet adapted to be marked by the implement.

35. The apparatus of claim 34 further including another two-coordinate direction display responsive to the signal for displaying the position and characteristics of the implement on the tablet.

36. The apparatus of claim 29 further including a two-coordinate direction display responsive to the signal for displaying the position and characteristics of the implement on the tablet.

37. A method of identifying a characteristic and position of an implement on a position sensing tablet having a two coordinate direction coil arrangement associated therewith, the implement having one of plural characteristics and including a tuned circuit having one of plural different resonant frequencies, comprising supplying AC energy at the plural different resonant frequencies to the coil arrangement;

the tuned circuit on the implement when placed in proximity to the tablet and coil arrangement causing changes in current flowing in the coil arrangement at said one frequency;

sensing changes in the current flowing in the coil arrangement at said different frequencies and responding to current changes at said frequencies for deriving a signal indicative of the position and characteristic of the implement on the tablet.

38. The method of claim 37 wherein the energy at the different frequencies is sequentially supplied to coils of the coil arrangement.

39. The method of claim 38 wherein the change is detected by supplying each of the coils during a first interval with the AC energy at one of the predetermined frequencies, sensing energy coupled back to one of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one predetermined frequency.

40. The method of claim 39 wherein the different frequencies are supplied in sequence to the coil arrangement such that in response to an implement having a first resonant frequency being on and not being on the tablet the first frequency is respectively derived for first and second durations prior to deriving a second frequency, said first duration being considerably in excess of said second duration.

41. The method of claim 40 wherein each of the first durations is divided into a plurality of said first and second intervals.

42. An eraser for supplying a signal to an electronic display and for removing a marking from a surface of a visual display comprising a housing, the housing including:

a surface for erasing the marking, first and second tuned circuits each having a reactance positioned in proximity to first and second opposite edges of the erasing surface, first and second switches which when activated respectively cause the first and second tuned circuits to have different first and second resonant frequencies, the first and second switches being positioned and arranged so that the first switch is activated in response to the first edge of the eraser being pushed against the display surface and the second switch is activated in response to the second edge of the eraser being pushed against the display surface.

43. The eraser of claim 42 wherein the eraser is cordless and not electric power supply is connected to the tuned circuits.

44. In combination, a position sensing tablet;

a two coordinate direction coil arrangement associated with the tablet;

a two-coordinate direction display superposed with the tablet;

multiple implements for modifying markings on the display, each of said implements having a different characteristic associated therewith and including a tuned circuit having a different resonant frequency for each characteristic;

means for supplying AC energy at the different resonant frequencies to the coil arrangement;

the tuned circuit on the implements when the implements are placed in proximity to the tablet and coil arrangement respectively causing changes in the currents flowing in the coil arrangement at said different frequencies; and

means for sensing changes in the current flowing in the coil arrangement at said different frequencies and responsive to current changes at said frequencies for deriving a signal indicative of the position and characteristics of markings by the implements on the display.

45. The combination of claim 44 wherein the energy at the different frequencies is sequentially supplied to different coils of the coil arrangement.

46. The combination of claim 45 wherein the changes are detected by supplying each of the coils during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to one of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one predetermined frequency.

47. The combination of claim 46 further including another two coordinate display responsive to the signal indicative of the position of the markings and the identification of the implements.

48. The combination of claim 47 wherein the implements include a plurality of markers, each of said markers being for a different color, said another display displaying the position and colors of the markings made by each of the markers on the first named display.

49. The combination of claim 44 further including another two coordinate display responsive to the signal indicative of the position of the marking and the characteristics of the implements.

50. The combination of claim 49 wherein the implements include a plurality of markers, each of said markers being for a different color, said another display displaying the position and colors of the markings made by each of the markers on the first named display.

51. The combination of claim 44 wherein each of said implements is cordless and no electric power supply is connected to the tuned circuits thereof.

52. The combination of claim 50 wherein one of the implements is a marker and another of the implements is an eraser for markings of the marker, said signal being indicative of markings by the marker as modified by the eraser, the another display being responsive to the signal to indicate the markings as modified by the eraser.

53. The combination of claim 52 wherein the implements include a plurality of markers, each of said markers being for a different color, said another display displaying the position and colors of the markings made by each of the markers on the first named display.

54. In combination, a position sensing tablet;

a two coordinate coil arrangement associated with the tablet;

a two coordinate direction display superposed with the tablet;

plural markers for the display, each of the markers being for a different color on the display;

each of the markers including a tuned circuit having a different resonant frequency, means for supplying AC energy at the different resonant frequencies to the coil arrangement, the tuned circuits on the markers when the markers are placed in proximity to the tablet and coil arrangement causing changes in currents flowing in coils of the coil arrangement at said different frequencies; and

means responsive to energy coupled between the tablet and markers for deriving a signal indicative of the position of the colors of markings by the markers on the display, said last named means sensing changes in current flowing in the coil arrangement at said different frequencies.

55. The combination of claim 54 wherein the energy at the different frequencies is sequentially supplied to different coils of the coil arrangement.

56. The combination of claim 55 wherein the change is detected by supplying each of the coils during a first interval with the AC energy at one of the predetermined frequencies, the means for sensing being activated to be responsive to energy coupled back to one of the coils from the tuned circuit during a second interval while the particular coil is not supplied with the AC energy at the one predetermined frequency.

57. The combination of claim 56 further including another two coordinate color-display responsive to the signal indicative of the position of markings for displaying the position and color of the markings.

58. The combination of claim 54 further including another two coordinate color-display responsive to the signal indicative of the position of markings for displaying the position and color of the markings.

59. The combination of claim 54 wherein said markers are cordless and no electric power supply is connected to the tuned circuits thereof.

60. A method of displaying a polychromic image comprising marking a first two coordinate direction display with plural markers each having a different color and a tuned circuit with a different resonant frequency thereon, applying plural frequencies to a two coordinate direction coil arrangement, the coil arrangement coupling the plural frequencies to each marker as it is marking the first display, activating the coil arrangement so it is responsive to an interaction of each applied frequency and each tuned circuit to provide an indication of the color and position of the mark being made by each marker on the first display, and displaying on a second two coordinate direction display the position and color of the mark made by each marker on the first display by responding to the indication.

61. The method of claim 60 wherein each of the frequencies is sequentially applied to the markers on the display.

62. The method of claim 61 wherein the frequencies are applied during a first interval and the response to the interaction is derived during a second interval while the frequencies are not applied.

63. The method of claim 62 wherein the different frequencies are supplied in sequence to the coil arrangement such that in response to an implement having a first resonant frequency being on and not being on the tablet said first resonant frequency is respectively derived for first and second durations prior to deriving a second frequency, said first duration being considerably in excess of said second duration.

64. The method of claim 63 wherein each of the first durations is divided into a plurality of said first and second intervals.

65. A method of indicating the position of an image on a two coordinate direction display, comprising marking the display with a marker, erasing from the display at least a portion of marks made by the marker, said marker and eraser respectively having tuned circuits with first and second resonant frequencies, activating a two coordinate direction coil arrangement so it applies said first and second resonant frequencies to the marker and the eraser as they respectively mark and erase the display, and activating the coil arrangement to be responsive to an interaction of the applied first and second frequencies with the tuned circuits to derive an indication of the position of the marking on the display as modified by the eraser.

66. The method of claim 65 further comprising displaying the position of the marking on the display as modified by the eraser by applying the indication to another two coordinate direction display.

67. The method of claim 66 wherein each of the frequencies is sequentially applied to the markers on the display.

68. The method of claim 67 wherein the frequencies are applied during a first interval and the response to the interaction is derived during a second interval while the frequencies are not applied.

69. The method of claim 68 wherein the different frequencies are supplied in sequence to the coil arrangement such that in response to an implement having a first resonant frequency being on and not being on the tablet, said first resonant frequency is respectively derived for first and second durations prior to deriving a second frequency, said first duration being considered in excess of said second duration.

70. The method of claim 69 wherein each of the first durations is divided into a plurality of said first and second intervals.

71. The method of claim 65 wherein each of the frequencies is sequentially applied to the markers on the display.

72. The method of claim 71 wherein the frequencies are applied during a first interval and a response to the interaction is derived during a second interval while the frequencies are not applied.

73. The method of claim 72 wherein the different frequencies are supplied in sequence to the coil arrangement such that in response to an implement having a first resonant frequency being on and not being on the tablet said resonant frequency is respectively derived for first and second durations prior to deriving a second frequency, said first duration being considered in excess of said second duration.

74. An eraser for supplying a signal to an electronic display and for removing a marking from a surface of a visual display comprising a housing, the housing including:

a surface for erasing the marking, a tuned circuit having a reactance positioned immediately behind the eraser surface, and switch means activated in response to the erasing surface being pressed against the display surface for connecting elements of the tuned circuit, including said reactance, together so they have a predetermined resonant frequency while the erasing surface is pressed against the display surface.

75. The eraser of claim 74 wherein the switch means includes first and second switches positioned and arranged so that the first switch is activated in response to a first edge of the eraser being pushed against the display surface and the second switch is activated in response to a second edge of the eraser, opposite the first edge, being pushed against the display surface.

76. The eraser of claim 74 wherein the eraser is cordless and no electric power supply is connected to the tuned circuit.

77. The eraser of claim 74 wherein the reactance includes a coil having a longitudinal axis at a right angle relative to the erasing surface.

78. In combination, a position sensing tablet;

a two coordinate direction coil arrangement associated with the tablet;

a two coordinate direction display;

a first implement for causing marks to appear on the display;

a second implement for causing marks to be erased from the display;

the first implement including a tuned circuit having a first resonant frequency;

the second implement including a tuned circuit having a second resonant frequency;

means for supplying AC energy at the first and second resonant frequencies to the coil arrangement;

the implements are placed in proximity to the tablet and coil arrangement respectively causing changes in currents flowing in the coil arrangement of said first and second frequencies; and

means for sensing the changes in the current flowing in the coil arrangement at said first and second frequencies and responding to the current changes at said first and second frequencies for deriving a signal indicative of the position of markings by the first implement on the display as modified by the second implement.

79. The combination of claim 78 wherein the display is superposed with the tablet, the first implement and second implement being adapted to bear on the display.

80. The combination of claim 78 wherein the display is remote from the tablet and is responsive to the signal to indicate the position of the markings as modified by the second implement.

81. In combination, a position sensing tablet;

a two coordinate direction coil arrangement associated with the tablet;

multiple implements adapted to be moved relative to the tablet, each of said implements having a different characteristic associated therewith and including a tuned circuit having a different resonant frequency for each characteristic;

means for supplying AC energy at the different resonant frequencies to the coil arrangement;

the tuned circuits on the implements when the implements are placed in proximity to the tablet and coil arrangement respectively causing changes in the currents flowing in the coil arrangement at said different frequencies; and

means for sensing changes in the current flowing in the coil arrangement at said different frequencies and responsive to current changes at said frequencies for deriving a signal indicative of the position of the implements relative to the tablet and of the characteristics of the implements.

82. In combination, a position sensing tablet;

a two coordinate coil arrangement associated with the tablet;

a two coordinate direction display;

implement means for the display, said implement means including plural tuned circuits each having a different resonant frequency, a different resonant frequency being assigned to a different color for the display, means for supplying AC energy at the different resonant frequencies to the coil arrangement, the coil arrangement interacting with the tuned circuits on the implement means when the implement means is placed in proximity to the tablet to cause changes in currents flowing in coils of the coil arrangement at said different frequencies; and

means responsive to energy coupled between the tablet and the tuned circuits for deriving a signal indicative of the position of the colors of marks on the display resulting from the different tuned circuits being positioned relative to the tablet, said last named means sensing changes in current flowing in the coil arrangement at said different frequencies.

83. A method of displaying a polychromic image comprising moving implement means having tuned circuit means with resonant frequencies, each associated with a different color, relative to a tablet having a two coordinate direction coil arrangement;

applying plural frequencies to the two coordinate direction coil arrangement, the coil arrangement coupling the plural frequencies to the implement means as it is moved relative to the tablet;

activating the coil arrangement so it is responsive to an interaction of each applied frequency and each tuned circuit resonant frequency to provide an indication of the position and color assigned to the resonant frequency of the implement means relative to the tablet, and displaying on a two coordinate direction display the position and color associated with the movement of the implement means relative to the tablet by responding to the indication.

84. A method of indicating the position of the effective movement of a first implement that causes marks to appear on a two coordinate direction display, the effective movement of the first implement being modified by a second implement that causes the marks to be erased from the display, comprising moving the first and second implements relative to a tablet so that some of the area traversed by the first implement relative to the tablet is subsequently traversed by the second implement, said first and second implements respectively having tuned circuits with first and second resonant frequencies, activating a two coordinate direction coil arrangement of the tablet so it applies said first and second resonant frequencies to the first and second implements as they are respectively traversed relative to the tablet, and activating the coil arrangement to be responsive to an interaction of the applied first and second frequencies with the tuned circuits to derive an indication of the position of the marks on the display as modified by the erasing action of the second implement.

86. An electronic writing tablet apparatus comprising:

a writing surface,

a tool for modifying an image on the surface including a tuned circuit having a resonant frequency;

means for sensing the presence of the tool relative to said writing surface, said means including electric wave generating means for generating an electric wave with plural frequency components, one having a value equal to said resonant frequency, and an electric wave detection means for detecting an electric wave reflected by said tuned circuit;

said sensing means including coordinate detection means responsive to the electric wave reflected from said tool and generated by said generating means for detecting a coordinate corresponding to the position of said tool..Iaddend..Iadd.

87. The electronic tablet apparatus of claim 86 wherein said electric wave generating means and said electric wave detection means include x- and y-direction loop coil groups..Iaddend..Iadd.88. In combination, a position sensing tablet;

a two coordinate direction coil arrangement associated with the tablet;

a tool means adapted to be moved relative to the tablet and coil arrangement, the tool means including tuned circuit means having first and second resonant frequencies;

means for supplying AC energy having first and second frequency components to the coil arrangement;

the tuned circuit means on the tool means when the tool means is placed in proximity to the tablet and coil arrangement causing a change in a current flowing in the coil arrangement, and means for sensing the change in the current flowing in the coil arrangement and responding to the current change for deriving a signal indicative of coordinates of the tool means relative to the tablet and coil means..Iaddend..Iadd.89. The combination of claim 88 wherein said tool means is cordless and no electric power supply is connected to the tuned circuit means thereof..Iaddend..Iadd.90. The combination of claim 88 wherein the first and second frequency components are respectively equal to the first and second resonant frequencies..Iaddend.