Rotary circuit control devices with changeable graphics

• US 5,936,613 A
• Filed: 08/11/1997
• Issued: 08/10/1999
• Est. Priority Date: 11/05/1993
• Status: Expired due to Fees

• Current Assignee: Intertactile Technologies Corporation
• Original Assignee: Intertactile Technologies Corporation
• Inventors: Jaeger, Denny, Twain, Kenneth M.
• Primary Examiner(s): Liang, Regina
• Application Number:
  US08/909,114
• Time in Patent Office: 729 Days
• Field of Search: 345/168, 345/169, 345/170, 345/171, 345/172, 345/173, 345/184, 345/905, 341/22, 341/23, 341/28, 341/33, 341/34
• US Class Current: 345/172
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/1345 Conductors connecting electrodes to cell terminals
• CPC Class Codes: G06F 1/1601 Constructional details related to the housing of computer displays, e.g. of CRT monitors, of flat displays constructional details related to flat displays integrated in a portable computer, e.g. laptop, handheld computer G06F1/1637; constructional details related to television receivers H04N5/64
• CPC Class Codes: G06F 2200/1611 CRT monitor
• CPC Class Codes: G06F 2200/1612 Flat panel monitor
• CPC Class Codes: G06F 3/0238 Programmable keyboards key guide holders G06F3/0224
• CPC Class Codes: G06F 3/0312 for tracking the rotation of a spherical or circular member, e.g. optical rotary encoders used in mice or trackballs using a tracking ball or in mouse scroll wheels tracking relative movement in co-operation with a regularly or irregularly patterned surface, e.g. as in optical mice G06F3/0317; constructional details of scroll or thumb-wheels G06F3/0362; optical rotary encoders G01D5/3473
• CPC Class Codes: G06F 3/0362 with detection of 1D translations or rotations of an operating part of the device, e.g. scroll wheels, sliders, knobs, rollers or belts
• CPC Class Codes: G06F 3/0421 by interrupting or reflecting a light beam, e.g. optical touch-screen
• CPC Class Codes: H01H 2009/184 Illumination of symbols by using laser light
• CPC Class Codes: H01H 36/008 Change of magnetic field wherein the magnet and switch are fixed, e.g. by shielding or relative movements of armature for reed switches H01H36/002
• CPC Class Codes: H01H 9/181 using a programmable display, e.g. LED or LCD

Abstract

An electrical circuit control of the type having a knob which is turned by an operator to vary a circuit condition is affixed to the face of an electronic image display device and at least a portion of the knob overlays the image display area. This enables display of instantly changeable calibration marks and/or other graphics in close proximity to the circuit control including at locations immediately adjacent to the perimeter of the knob. Electronic components of the control are contained within the knob and a base member at the front of the panel. Components of this kind may be embedded in or attached to the knob itself enabling easy repair by simply replacing the knob and/or may be contained in an easily replaced carrier that fits within the base. Knob motion sensors include radio frequency sensors, capacitive sensors, Hall effect sensors and photoelectric sensors among others and enable the controls to be compact, durable and enable economic manufacture. A signal processor can convert initial values of the control signal produced at successive settings of a control to differing assigned values. The conversion method is applicable to sliding knob controls as well as rotary controls and enables imparting of any desired response curve to a circuit control without regard to the actual response of the knob motion sensor.

Claims

1. A control device for an electrical circuit which control device has a base member and a turnable knob coupled thereto, the knob being turnable to any of a plurality of different angular orientations to change an electrical condition in the circuit, wherein the improvement comprises:

said base member and knob being disposed in front of an electronic image display device which has an image display area at which changeable images are displayed, and wherein at least a portion of said knob overlays the image display area of said image display device, and

a control signal producing circuit which produces a signal having a variable value determined by the angular orientation of said knob.

2. The control device of claim 1 wherein said image display device has a transparent cover plate at said image display area thereof, said base member being affixed to said transparent cover plate.

3. The control device of claim 1 wherein said control signal producing circuit has electronic components which are contained within at least one of said base member and said knob in front of said image display device.

4. The control device of claim 3 wherein said turnable knob is detachable from said base member and wherein at least a portion of said components of said control signal producing circuit are embedded within said turnable knob and are detachable from said base member therewith.

5. The control device of claim 3 wherein said turnable knob is detachable from said base member and wherein at least a portion of said components of said control signal producing circuit are attached to a removable and replaceable carrier which is fitted into said base member between said turnable knob and said image display device.

6. The control device of claim 5 wherein said electronic display device has a transparent cover plate to which said base member is affixed, further including a plurality of electrical conductors extending along a surface of said cover plate for connecting said control device to a controlled circuit, said base member having a floor which faces said cover plate and which has a plurality of passages which extend towards said cover plate, said carrier having a plurality of conductive pins which extend into said passages to connect said electronic components with said electrical conductors.

7. The control device of claim 5 wherein said electronic display device has a transparent cover plate to which said base member is affixed, further including a plurality of electrical conductors extending along a surface of said cover plate for connecting said control device to a controlled circuit and at least a pair of resilient conductive contacts which are connected to separate ones of said electrical conductors, said resilient conductive contacts having first ends which are secured to said base member and second ends configured and positioned to clasp said carrier.

8. The control device of claim 1 wherein said image display device is a panel display of the form having internal x-busbars which extend in orthogonal relationship with y-busbars and which activate different combinations of image pixels at different times to provide changeable images.

9. The control device of claim 1 wherein said image display device is a cathode ray tube form of display device.

10. The control device of claim 1 wherein said image display device has a transparent cover plate at said image display area thereof, said base member being affixed to said transparent cover plate, further including at least a pair of electrical conductors which extend along a surface of said transparent cover plate from said base member to an edge of said image display area for connecting said control device to said electrical circuit, and wiper contact means for electrically connecting said electrical conductors with components which are secured to said turnable knob, said wiper contact means being contained within said turnable knob and said base member in front of said image display device.

11. The apparatus of claim 1 further including an image display device controller coupled to said image display device and which causes said image display device to present indicia at said image display area including indicia which are adjacent to said turnable knob at spaced apart locations around the perimeter thereof.

12. The control device of claim 1 wherein said control device produces an initial sequence of control signal values at successive settings of said turnable knob, further including signal processing means for converting said initial sequence of control signal values to a differing sequence of assigned control signal values to compensate for deviations of said initial sequence of control signal values from a desired sequence of control signal values.

13. The control device of claim 1 wherein said image display device has a transparent cover plate at said image display area thereof and wherein said base member is affixed to said transparent cover plate and wherein at least one opening extends into the transparent cover plate at the location of said circuit control device, said base member having a protrusion which extends into said opening.

14. The apparatus of claim 13 wherein a plurality of said control devices are attached to said transparent cover plate and wherein said transparent cover plate has a plurality of said openings including at least one opening at the location of each of said plurality of control devices, each of said control devices having at least one protrusion which extends into an opening at the location of the control device, said protrusions and openings having a keyed configuration wherein particular ones of said protrusions are fittable only in particular ones of said openings.

15. The apparatus of claim 13 wherein an electrical conductor extends along a surface of said transparent cover plate to connect said control device with a controlled circuit and wherein said protrusion is an electrical connector pin which connects an electronic component of said control device with said electrical conductor.

16. The apparatus of claim 13 wherein said transparent cover plate has a control signal conductor extending along a back surface of said cover plate and wherein said opening extends through said transparent cover plate, said protrusion being formed at least in part of electrically conductive material and being electrically connected to said control signal conductor and to a control signal producing circuit within said knob and base member.

17. The apparatus of claim 1 wherein at least a portion of said turnable knob is formed of electrically conductive material, and wherein said control signal producing circuit includes a touch sensing circuit electrically connected to said electrically conductive material and wherein said control signal producing circuit produces a circuit control signal in response to an operator touching said turnable knob.

18. The apparatus of claim 1 wherein said turnable knob turns about an axis of rotation and wherein said base member forms a circular chamber situated between said turnable knob and a front surface of said image display device, wherein said control signal producing circuit includes a circular discontinuous electrical resistance situated in said chamber and which is centered on said axis of rotation, a first wiper contact carried by said turnable knob in position to contact said resistance and to travel therealong as said knob is turned, a second contact secured to said turnable knob and being electrically connected to said first wiper contact, and at least a first and a second conductor extending along said transparent cover plate, said first conductor being connected to said electrical resistance to apply voltage thereto and said second conductor being electrically connected to said second wiper to transmit a selectively variable voltage to an electrical circuit.

19. The apparatus of claim 18 wherein said base member is of annular configuration and wherein said electrical resistance is a trace of resistive material bonded to said front surface of said transparent cover plate.

20. The apparatus of claim 18 wherein said base member is cup shaped and has a base region which is adjacent to said front surface of said image display device, said electrical resistance being a trace of resistive material bonded to base region within said base member.

21. The apparatus of claim 18 wherein an electrically conductive surface extends around said axis of rotation within said chamber in spaced apart relationship with said electrical resistance and wherein said second contact is a wiper contact positioned to contact said conductive surface and to travel along said conductive surface as said knob turns, said second conductor being electrically connected to said conductive surface.

22. The apparatus of claim 1 wherein said turnable knob has an internal chamber, wherein said control signal producing circuit includes an electrical resistance disposed in said chamber and extending in parallel relationship with an axis of rotation of said turnable knob, said resistance being secured to said transparent cover plate, a threaded rod extending along said axis of rotation within said internal chamber and being secured to said turnable knob, said threaded rod being formed of electrically conductive material, an internally threaded wiper sleeve disposed on said threaded rod and which engages the threads of said rod, said internally threaded sleeve having a projection which contacts said electrical resistance, a wiper guide secured to said transparent cover plate and extending into said internal chamber of said knob and being positioned to prevent rotation of said wiper sleeve when said knob is rotated whereby said wiper sleeve travels along said electrical resistance when said knob is turned, at least one first conductor secured to said transparent cover plate and being electrically connected to said electrical resistance to apply voltage thereto and a second conductor secured to said transparent cover plate for receiving an output voltage from said wiper sleeve.

23. The control device of claim 1 further including an electrically conductive body carried by said turnable knob at a location which is offset from an axis of rotation thereof, wherein said control signal producing circuit includes a pair of spaced apart electrical coils disposed at fixed locations which are offset from said axis of rotation, each of said electrical coils being an inductive component of the resonant circuit of a separate one of a pair of electrical oscillators, and a digital data processor conditioned to detect changes in the ratio of the frequencies of said oscillators produced by movement of said conductive body and to generate an electrical circuit control signal that varies in response to changes of the ratio.

24. The control device of claim 23 wherein said image display device has a transparent cover plate at said image display area thereof, said base member being affixed to said transparent cover plate, and wherein said electrical coils are secured to the back surface of said transparent cover plate.

25. The control device of claim 23 wherein said electrical coils are secured to a circuit board which is situated behind said image display device.

26. The control device of claim 23 wherein said electrical coils have an angular spacing from each other of about ninety degrees relative to said axis of rotation.

27. The control device of claim 23 wherein said electrical oscillators are disposed within said base member.

28. The control device of claim 1 further including an electrically conductive body disposed within said base member at a location which is offset from an axis of rotation of said knob, wherein said control signal producing circuit includes a pair of spaced apart electrical coils carried by said knob at locations which are offset from said axis of rotation, each of said electrical coils being an inductive component of the resonant circuit of a separate one of a pair of electrical oscillators, and a digital data processor conditioned to detect changes in the ratio of the frequencies of said oscillators produced by movement of said conductive body and to generate an electrical circuit control signal that varies in response to changes of the ratio.

29. The control device of claim 28 wherein the region containing said conductive body and said electrical coils is substantially enclosed by electrically conductive shielding material.

30. The control device of claim 1 wherein said image display device has a transparent cover plate at said image display area thereof, said base member being affixed to said transparent cover plate, wherein said control signal producing circuit includes at least one elongated first capacitor plate disposed between said transparent cover plate and said turnable knob and which curves around an axis of rotation thereof, said first capacitor plate having a width which progressively changes along at least a portion thereof, a second capacitor plate secured to said turnable knob in spaced apart relationship to said first capacitor plate in position to be traveled along said first capacitor plate as said knob is turned, said second capacitor plate being sized to extend along only a portion of the first capacitor plate, said first and second capacitor plates being part of the resonant circuit of an electrical oscillator, and a frequency detector coupled to said oscillator which outputs a circuit control signal which changes in response to changes of the frequency that is detected by the frequency detector.

31. The control device of claim 30 wherein said first capacitor plate is a trace of electrically conductive material bonded to said front surface of said transparent cover plate.

32. The control device of claim 30 wherein said first capacitor plate is a trace of electrically conductive material bonded to said base member.

33. The control device of claim 30 further including a curved band of electrical conductor extending alongside said first capacitor plate in spaced apart relationship therewith and being electrically connected to said oscillator, said second capacitor having a wiper contact positioned to travel along said band of electrical conductor as said knob is turned.

34. The control device of claim 30 further including a third capacitor plate extending in the plane of said first capacitor plate in spaced apart relationship therewith and which also curves around said axis of rotation of said turnable knob, said third capacitor plate having a width which progressively changes along at least a portion of thereof and wherein said third capacitor plate becomes progressively wider in the same direction that said first capacitor plate becomes progressively wider, said first and third capacitor plates being electrically connected to said oscillator to form the capacitive component of the resonant circuit thereof, and wherein said second capacitor plate faces both said first capacitor plate and said third capacitor plate in spaced apart relationship therewith.

35. The control device of claim 1 wherein said control signal producing circuit includes a light source and a photoelectric light detector which are contained within said base member and turnable knob, said photoelectric light detector being positioned to detect light which travels from said light source to said photoelectric light detector along a light path, and means for altering a characteristic of the detected light in response to turning of said turnable knob to enable detection of the angular orientation of said turnable knob.

36. The apparatus of claim 35 wherein said light source directs light towards a surface of said turnable knob and wherein said means for altering a characteristic of the detected light includes a mirror disposed on said surface in position to reflect light from said light source to said photoelectric light detector, said mirror having a degree of reflectivity that progressively changes at successive locations along a circular path on the mirror that is centered on the axis of rotation of the turnable knob.

37. The apparatus of claim 35 wherein said light source directs light towards a surface of said turnable knob, further including a mirror disposed on said surface in position to reflect light from said light source to said photoelectric light detector, and wherein said means for altering a characteristic of the detected light includes a light modulating disk having a degree of light transmissivity that progressively changes at successive locations along a circular path on the disk that is centered on the axis of rotation of the turnable knob and which is intersected by said light path.

38. The apparatus of claim 35 having a pair of said photoelectric light detectors and wherein said light source directs light towards a surface of said turnable knob, further including a mirror disposed on said surface in position to reflect light from said light source to each of said photoelectric light detectors, and wherein said means for altering a characteristic of the detected light includes a light modulating disk having opaque areas that alternate with light transmissive areas along a circular path on the disk that is centered on the axis of rotation of the turnable knob and which is intersected by said light path, said opaque areas and light transmissive areas being configured to transmit light to both of said photoelectric light detectors at a first angular setting of said turnable knob and to transmit light only to a first of said photoelectric light detectors at the following angular setting of said turnable knob and to transmit light to neither of said photoelectric light detectors at the next angular setting of said turnable knob and to transmit light only to a second of said photoelectric light detectors at the following setting of said turnable knob as said knob is turned in one angular direction.

39. The apparatus of claim 35 further including an opaque light barrier extending between said light source and said photoelectric light detector.

40. The apparatus of claim 35 further including image display device controller means for causing said image display device to present an image of a dark area at the region of said image display area that is behind said light source and said photoelectric light detector.

41. The apparatus of claim 35 wherein said base member is affixed to a front surface of a transparent cover plate of said image display device and wherein said light source and said photoelectric light detector are situated at a back surface of said transparent cover plate.

42. The control device of claim 1 wherein said image display device has a transparent cover plate at said image display area thereof, said base member being affixed to said transparent cover plate, further including a magnet secured to said turnable knob at a location which is offset from an axis of rotation thereof, wherein said control signal producing circuit includes at least a first Hall effect sensor and a second Hall effect sensor disposed between said turnable knob and said transparent cover plate which Hall effect sensors are spaced apart from each other, and a signal processor electrically coupled to said Hall effect sensors and being conditioned to produce a circuit control signal that varies in response to variations of the resistances of said Hall effect sensors caused by rotary motion of said turnable knob and magnet.

43. The control device of claim 42 further including a third Hall effect sensor disposed between said turnable knob and said transparent cover plate and being electrically coupled to said signal processor, said third Hall effect sensor being offset from said axis of rotation of said turnable knob and being spaced apart from said first and second Hall effect sensors.

44. The control device of claim 1 further including a magnet secured to said turnable knob at a location which is offset from an axis of rotation thereof and wherein said control signal producing circuit includes a magnetic pad which generates an output signal in response to rotary movement of the magnet, said magnetic pad being behind said image display device.

45. The apparatus of claim 1 wherein said turnable knob has an opening into which said base member extends, said base member having a circumferential groove situated within said opening and said turnable knob having a slot in a side wall thereof which bounds said opening, further including an elongate loop of resilient spring material disposed in said opening, said loop having a first end which is secured to said side wall of said turnable knob and a second end which extends into said slot, said loop being proportioned to snap engage in said groove as said turnable knob is forced into said base member.

46. The apparatus of claim 1 wherein one of said base member and said turnable knob has an opening into which a peripheral portion of the other of said base member and said knob is fitted, a portion of said opening being narrower than said peripheral portion whereby said turnable knob snap engages on said base member.

47. The apparatus of claim 1 wherein said turnable knob has a base with a circular opening therein that is centered on an axis of rotation of said turnable knob and wherein said base member has an annular peripheral portion which is seated in said opening and which has a diameter conforming to the diameter of said opening, further including a post extending along said axis of rotation within said turnable knob and having a flanged end which extends towards said transparent cover plate, and a socket engaging said flanged end of said post and being secured to said transparent cover plate.

48. The apparatus of claim 1 wherein said image display device is a panel display having segmented electrodes which are energized to produce changeable images.

49. A control device for an electrical circuit which control device comprises:

a base member and a movable member attached thereto which movable member is manipulated by an operator to change a setting of said control device, said base member being affixed to an electronic image display screen at a location which is at least partially within an image display area thereof,

a display screen controller coupled to said image display screen and being conditioned to cause display of an image which conveys information pertinent to operation of said control device,

a signal producing circuit situated at said location and which requires input of an electrical voltage, and

a photovoltaic cell for converting light to electrical energy, said photovoltaic cell being disposed within said base member and being connected to said signal producing circuit to supply said electrical voltage thereto, said photovoltaic cell being positioned to receive light which is produced by said image display screen.

50. A method of processing control signals produced by an electrical circuit control device of the type in which manual movement of a first component to successive ones of a series of different settings causes a second component to output a circuit control signal that changes during the course of the movement to identify the successive settings of the first component, wherein irregularities of manufacture may cause the original values of the control signal produced at the successive settings to differ from desired values in an initially unknown manner, comprising the steps of:

detecting and storing the initially unknown original value of said control signal at each of a series of the different settings of said first component,

designating an assigned value for the control signal at each of said series of different settings of said first component which assigned values are the desired values of the control signal at the different settings,

storing each assigned value in association with the corresponding original value,

thereafter responding to movement of said first component to any particular one of said series of different settings thereof by converting the detected original value of said control signal at that setting to the associated assigned value.

51. The method of claim 50 including the further steps of correcting for the effects of wear within said electrical circuit control device by:

repositioning said first component at each of a series of said different settings thereof,

detecting changed original values at any of said different settings of said series,

changing the original value that is stored in association with the assigned value at each setting of said first component at which a changed original value is detected.

52. A control device for an electrical circuit which control device has a base member and a turnable knob coupled thereto, the knob being turnable to any of a plurality of different angular orientations to change an electrical condition in the circuit, wherein the improvement comprises:

said base member being affixed to an electronic image display device which has an image display area at which changeable images are displayed, said base member and knob being in front of said image display device and wherein at least a portion of said knob overlays the image display area of said image display device, further including at least one magnet secured to one of said base member and said knob, first and second Hall effect sensors secured to the other of said base member and said knob and being at locations which are within the magnetic field of said magnet, and a signal processor electrically coupled to said Hall effect sensors and being conditioned to produce an electrical circuit control signal that varies in response to variations of the resistances of said Hall effect sensors caused by turning of said knob.

53. The control device of claim 52 wherein said knob turns about an axis of rotation thereof and wherein said magnet is positioned to be intersected by said axis of rotation with at least one of the magnetic poles of the magnet being offset from the axis of rotation.

54. The control device of claim 53 wherein said magnet has a circular disk shape and is substantially centered on said axis of rotation.

55. The control device of claim 53 wherein said magnet has a north magnetic pole that is offset from said axis of rotation in a first direction and a south magnetic pole that is offset from said axis of rotation in a second opposite direction.

56. The control device of claim 53 wherein said magnet has first and second north magnetic poles and first and second south magnetic poles and wherein said magnetic poles are each offset from said axis of rotation of said knob, said first north magnetic pole and said first south magnetic pole being at one side of said axis of rotation and said second north magnetic pole and second south magnetic pole being at an opposite side of said axis of rotation, said first north magnetic pole and first south magnetic pole being closer to said Hall effect sensors than said second north magnetic pole and said second south magnetic pole.

57. The control device of claim 53 wherein said Hall effect sensors have magnetic field sensitive faces which extend in parallel relationship with said axis of rotation of said knob and wherein said first Hall effect sensor extends at right angles to said second Hall effect sensor and has an end which faces a mid-section of said second Hall effect sensor, said Hall effect sensors being situated between said magnet and said base member of said control device.

58. The control device of claim 53 wherein said first Hall effect sensor overlays said second Hall effect sensor, said Hall effect sensors having magnetic field sensitive faces that are parallel to each other and which extend at right angles to said axis of rotation of said knob in angled relationship to each other.

59. The control device of claim 53 wherein said Hall effect sensors have magnetic field sensitive faces which face towards said axis of rotation of said knob and which are angled relative to each other and in parallel relationship with said axis of rotation of said knob and wherein said magnet extends along said axis of rotation and has north and south magnetic poles that are at opposite sides of said axis of rotation.

60. The control device of claim 52 further including a magnetic flux concentrating body of ferromagnetic material disposed within the knob and base membere member and being positioned to concentrate magnetic flux therein.

61. The control device of claim 52 wherein said knob is formed at least in part of ferromagnetic material.

62. The control device of claim 52 wherein said knob has an interior chamber into which said base member extends, said magnet being seated within said knob, said Hall effect sensors being within said interior chamber of said knob and being secured to said base member.

63. A control device for an electrical circuit which control device has a base member and a turnable knob coupled thereto, the knob being turnable to any of a plurality of different angular orientations to change an electrical condition in the circuit, wherein the improvement comprises:

said base member being affixed to an electronic image display device which has an image display area at which changeable images are displayed, said base member and knob being in front of said image display device and wherein at least a portion of said knob overlays the image display area of said image display device, wherein said knob turns about an axis of rotation that intersects said base member, further including at least one magnet and at least one Hall effect sensor secured to one of said knob and said base member, said magnet and Hall effect sensor being spaced apart in a radial direction relative to said axis of rotation of said knob, an annular body of ferromagnetic material secured to the other of said knob and said base member, said annular body of ferromagnetic material being centered on said axis of rotation and being positioned to extend within the magnetic field of said magnet, wherein the expanse of said body of ferromagnetic material in a direction parallel to said axis of rotation progressively changes at successive locations around the circumference of said body of ferromagnetic material.

64. The control device of claim 63 wherein successive segments of said annular body of ferromagnetic material pass between said magnet and said Hall effect sensor as said knob is turned.

65. The control device of claim 63 wherein one of said magnet and said Hall effect sensor has a first spacing from said axis of rotation and the other of said magnet and said Hall effect sensor has a second spacing from said axis of rotation that is greater than said first spacing, wherein said annular body of ferromagnetic material has a radial dimension that exceeds said first spacing and is smaller than said second spacing whereby successive portions of said annular body of ferromagnetic material pass between said magnet and said Hall effect sensor as said knob is turned.

66. The control device of claim 63 wherein said Hall effect sensor has a first spacing from said axis of rotation and said magnet and said Hall effect sensor has a second spacing from said axis of rotation, and wherein said annular body of ferromagnetic material has a radial dimension that exceeds both said first spacing and said second spacing.

67. A control device for an electrical circuit which control device has a base member and a turnable knob coupled thereto, the knob being turnable to any of a plurality of different angular orientations to change an electrical condition in the circuit, wherein the improvement comprises:

said base member being affixed to an electronic image display device which has an image display area at which changeable images are displayed, said base member and knob being in front of said image display device and wherein at least a portion of said knob overlays the image display area of said image display device wherein said knob and base member form a circuit housing and wherein said image display device has a transparent cover plate at said image display area and wherein said base member of said control device extends into an opening in said transparent cover plate, further including a position signal producing circuit disposed within said circuit housing and which produces a signal which varies in response to turning of said knob, a light source producing a light beam which encodes said signal, said light source being secured to said base member in position to direct said light beam into said transparent cover plate along a light path which is within said transparent cover plate and which extends from said opening to a location at an edge of said transparent cover plate, a light detector disposed at a marginal region of said image display device and being positioned to view said location and to receive light which has traveled along said light path and which outputs said signal in electrical form.

69. The control device of claim 67 wherein said image display device has a marginal region which adjoins said image display area, said radio receiver being situated within said marginal region of said image display device.

68. A control device for an electrical circuit which control device has a base member and a turnable knob coupled thereto, the knob being turnable to any of a plurality of different angular orientations to change an electrical condition in the circuit, wherein the improvement comprises:

said base member being affixed to an electronic image display device which has an image display area at which changeable images are displayed, said base member and knob being in front of said image display device and wherein at least a portion of said knob overlays the image display area of said image display device, wherein said knob and base member form a circuit housing, further including a signal producing circuit disposed within said circuit housing and which produces an electrical signal that varies in response to turning of said knob, a radio transmitter disposed in said housing in electrical connection with said signal producing circuit and which broadcasts said signal in radio frequency form, a signal receiving circuit situated away from said image display area of said image display device which signal receiving circuit includes a radio receiver which converts the radio frequency signal back into an electrical signal.

70. The control device of claim 68 further including means for attaching said base member to said image display device at any selected location within said image display area thereof.

71. The control device of claim 70 wherein said means for attaching said base member to said image display device enables detachment of said base member and knob therefrom.

72. The control device of claim 68 wherein said image display device includes a display controller conditioned to cause display of an image that pertains of operation of said control device, further including position sensing means for producing a position signal which identifies the location of said base member and knob on said screen and wherein said display controller positions said image within said image display area in response to said position signal.

73. The control device of claim 72 wherein said image display area has first and second opposite edges and third and fourth opposite edges which extend between said first and second opposite edges and wherein said position sensing means includes a row of light detectors extending along said first edge and another row of light sources extending along said third edge, said position sensing means further including a row of light sources extending along said second edge and being positioned to direct light to the detectors at said first edge along a plurality of parallel light paths and another row of light sources extending along said fourth edge and being positioned to direct light to the detectors at said third edge along another plurality of parallel light paths, and wherein said position sensing means detects the location of said base member and knob by monitoring said light detectors to detect blockage of particular ones of said light paths.

74. A control device for an electrical circuit which control device has a base member and a turnable knob coupled thereto, the knob being turnable to any of a plurality of different angular orientations to change an electrical condition in the circuit, wherein the improvement comprises:

said base member being affixed to an electronic image display device which has an image display area at which changeable images are displayed, said base member and knob being in front of said image display device and wherein at least a portion of said knob overlays the image display area of said image display device, further including a continuous annular band of electrically resistive material situated between said turnable knob and said image display device, a wiper contact secured to said turnable knob and wherein a portion of said wiper contact bears against said continuous annular band of electrically resistive material and wherein said portion of said wiper contact travels along said annular band of electrically resistive material in contact therewith as said knob is turned, an electrical voltage source having a positive terminal and a negative terminal, one of said terminals being electrically connected to said wiper contact and the other of said terminals being electrically connected to said annular band of electrically resistive material at a first fixed location thereon, a first analog to digital signal converter having an input connected to said annular band of electrically resistive material at a second fixed location thereon which second fixed location is spaced apart from said first fixed location, a second analog to digital signal converter having an input connected to said annular band of electrically resistive material at a third fixed location thereon which third fixed location is spaced apart from both of said first fixed location and said second fixed location, wherein said first and second analog to digital signal converters output a pair of location signals one of which has a value determined by the current voltage at said second fixed location and the other having a value determined by the current voltage at said third fixed location, and a digital data processor which repetitively receives the pairs of location signals and which stores a plurality of different output signal values each being associated with a different pair of location signal values and which outputs a control signal having the value that is associated with the current pair of location signal values.

75. The control device of claim 74 wherein said first, second and third fixed locations are situated at 120°

angular intervals along said annular band of electrically resistive material.