Rotary circuit control devices with changeable graphics

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.

TECHNICAL FIELD 
This invention relates to devices which enable operator control of 
electrical circuits. More particularly the invention relates to circuit 
control devices of the type having a knob which is turned by an operator 
about an axis of rotation to vary an electrical signal and wherein a flat 
panel display produces changeable images that convey information pertinent 
to operation of the circuit control device. 
BACKGROUND OF THE INVENTION 
Traditional circuit control devices have a component, such as a turnable 
knob for example, that is physically moved by the operator in order to 
change an electrical condition in the controlled circuit. Potentiometers, 
rotary variable resistors and rotary encoders are examples of control 
devices of this type. Controls which require physical movement of a 
component by the operator are preferred by many persons and are less prone 
to erroneous input because of the tactile feedback which the operator 
receives. Some newer forms of circuit control such as touch screens for 
example do not provide this kind of feedback. 
Conventional controls which have a knob that is turned by the operator are 
not well adapted for use with some newer types of electronic circuit. The 
control typically requires calibration marks or other graphics around the 
perimeter of the knob and additional graphics which identify the function 
of the control and/or other information pertaining to operation of the 
control. In the conventional construction a shaft extends through a 
control panel. The turnable knob is in front of the control panel. Other 
components of the control device are behind the panel and are 
interconnected with the knob by the shaft. The graphics are permanently 
imprinted on the front of the control panel. Fixed graphics of this kind 
can severely limit the functions of the control device and can cause 
operator error under certain circumstances. This problem occurs in 
electronic systems in which a single control device is used for different 
purposes at different times. For example, a station selector knob of a 
radio requires one set of graphics when the radio is operating in the AM 
mode and a different set of graphics when the radio operates in the FM 
mode. Multiple function controls of this kind are also found in diverse 
other types of electronic apparatus such as computer alphanumeric 
keyboards and synthesizer keyboards for example. In many cases the 
operator must memorize the alternate functions of such controls or consult 
a chart or resort to such expedients as disposing an overlay on the 
controls that is imprinted with changed graphics. 
Problems of the above described kind can be alleviated by associating an 
image display screen with the circuit control device to enable display of 
instantly changeable images on or in the vicinity of the control. Under 
microprocessor control, graphics for the control device can be caused to 
change automatically when the function of the control device changes. 
Under some circumstances this can be beneficial at single function control 
devices as well as at multiple function controls. For example, the 
language of the labeling at a circuit control device can be caused to 
change instantly in response to operation of a language selection key. 
Prior rotary knob circuit control devices having an image display which 
provides instantly changeable graphics have characteristics that can be a 
source of problems at least under some circumstances. The control device 
and the image display screen are at different locations on the control 
panel and the image display area of the screen is bounded by a pheripheral 
region of the display which contains structural framing, seals and other 
components. The display cannot provide calibration marks around the 
perimeter of the knob and the sizable spacing between the graphics and the 
knob complicate the operator's task of associating graphics with the 
specific controls to which they relate. 
Some prior rotary controls of the above described kind have a thicker and 
bulkier construction then is desirable for some usages such as in 
constricted locations or where a thin control panel is to be disposed 
against a wall for for example. Some can be difficult and costly to 
manufacture particularly if precise control signals and a long operating 
life are desirable criteria. Others can produce only a very limited 
variety of different graphics. 
Repair or replacement of prior rotary knob control devices requires access 
to the back of the control panel. This complicates such operations and 
deters many users of control devices from personally undertaking the 
repair or replacement. 
The present invention is directed to overcoming one or more of the problems 
discussed above. 
SUMMARY OF THE INVENTION 
In one aspect the present invention provides a control device for an 
electrical circuit which control device has a base 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. The base is affixed to an image display device which provides 
changeable images and is at a location which is in front of the display 
device and which at least partially overlays the image display area of the 
display device. 
In another aspect of the invention a control device for providing operator 
selected control signals to a controlled electrical circuit includes an 
image display device having a screen with a transparent cover plate and an 
image area thereat at which information pertaining to operation of the 
control device is displayed. A base member is affixed to the cover plate 
at a location which is within the image display area. A knob engages on 
the base member and is turnable about an axis of rotation that extends at 
right angles to the cover plate. A control signal producing circuit 
produces a control signal indicative of the angular orientation of the 
knob about the axis of rotation, the control signal producing circuit 
being contained within the knob and base member. 
In another aspect the invention provides a method for processing control 
signals produced by an electrical circuit control device of the type in 
which manual movement of a first component along a series of different 
settings causes a second component to produce a circuit control signal 
that progressively changes during the course of the movement to identify 
the successive settings of the first component. Steps in the method 
include detecting and storing the original value of the control signal at 
each of a series of different settings of the first component. An assigned 
value for the control signal at each of the series of different settings 
of the first component is designated which assigned values may differ from 
the original values. Each assigned value is stored in association with the 
corresponding original value. Thereafter, movement of the first component 
is responded to by converting detected original values of the control 
signal to the associated assigned values. 
The operator manipulated turnable knob of embodiments of the invention is 
engaged on a base member which is affixed to the face of an image display 
device such as a flat panel display or a cathode ray tube for example. The 
knob is at a location which is at least partially within the image display 
area. This enables display of calibration marks and/or other graphics in 
close proximity to the perimeter of the turnable knobs of the circuit 
control devices. Consequently, the operator can more easily associate the 
graphics with the particular knob to which they relate and precise setting 
of the control is facilitated. The displayed graphics may change instantly 
and automatically when the function of the control device changes or when 
other conditions call for changed graphics. The invention further provides 
for detection of operator adjustment of a turnable knob by any of a 
variety of different and advantageous motion sensing means. In one form of 
the invention a data processing circuit alters the control signals which 
it receives in order to compensate for non-linearities at successive 
settings of the control device or to compensate for departures of the 
signal from a desired non-linear response to operator adjustment of the 
control. Electrical components of the control device which produce the 
control signal are contained within the knob and/or the base member at the 
front of the panel which supports the control device making them easily 
accessible for maintenance or replacement. In one form of the invention 
components of this kind are contained within a knob which may have a low 
cost construction and can be easily replaced as a unit by simply replacing 
the knob itself. 
The invention, together with further aspects and advantages thereof, may be 
further understood by reference to the following description of the 
preferred embodiments and by reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The invention is applicable to electrical circuit control devices of the 
type which have a knob that is manually turned to vary a circuit control 
signal or to turn a circuit on and off. As an initial example, FIG. 1 
depicts a potentiometer 11 type of circuit control device which has a 
rotary knob 12 that is grasped and turned by the operator to selectively 
vary an output voltage. Potentimeters typically have indicia 13 at angular 
intervals around the perimeter of the knob 12 which identify specific 
angular settings of the control device. 
Embodiments of the present invention differ from prior control devices that 
serve similar purposes in that the component which the operator 
manipulates, knob 12 in this example, is situated at least partially 
within the image display area 14 of an electronic image display device 16 
of one of the kinds that produces instantly changeable images. In this 
example of the invention the display device 16 is a flat panel display. At 
least some of the indicia 13 and/or other graphics pertinent to operation 
of the control device 11 are images generated by the flat panel display 
16. A flat panel display controller 17 which may be of known design is 
coupled to to the flat panel display 16 to cause display of the indicia 13 
and/or other appropriate graphics. 
Situating the knob 12 or other operator manipulated component in front of 
the image display area 14 in this manner enables display of the indicia 13 
at locations which are immediately adjacent to the knob 12 or the like. 
This avoids operator error with respect to associating the graphics with 
the particular control device to which they relate and enables precision 
setting of the control device. The arrangement can also enhance the 
appearance of control panels. Referring to FIGS. 2A and 2B, graphics 18 
may flash on and off, change form and purely decorative graphics may be 
displayed in the vicinity of the knob 12. The display controller 17 can 
change the graphics 13, 18 instantly when the function of the knob 12 is 
changed. 
For purposes of example, FIGS. 2A and 2B depict changing graphics 13, 18 
which are appropriate when the potentiometer 11 is the station selector of 
a radio which selectively operates in either an AM or FM mode. The 
potententiometer 11 can be used to control diverse other types of known 
circuits of the kind that respond to control signals in the form of a 
variable voltage or to digitized control signals which are originated in 
the form of a variable voltage. 
Referring jointly to FIGS. 3 and 4, the flat panel display 16 may be of any 
of the known types and may be of known design except as hereinafter 
described. For purposes of example, FIGS. 3 and 4 depict a flat panel 
display 16 of the TFEL (thin film electro-luminescent) type. Flat panel 
displays 16 of this kind are multi-layered and have a flat substrate 19 
which may be rigid or flexible and which may variously be formed of glass, 
ceramic or plastic. The substrate 19 is overlaid, in sequence, by a layer 
of row busbars 21, a first dielectric layer 22, a phosphor layer 23, a 
second dielectric layer 24, a layer of column busbars 26, a sealing and 
passivation layer 27 and a transparent cover plate 28 which may be glass 
or clear plastic. Row busbars 21 are parallel conductive traces bonded to 
substrate 19 and extend in an x-coordinate direction. Column busbars 26 
are parallel conductive traces deposited on the second dielectric layer 24 
and extend in a y-coordinate direction. The points at which the row and 
column busbars 21 and 26 cross each other define an array of image pixels 
29 at which the phosphor layer 23 emits light when a voltage difference is 
applied across the row and column busbars that cross each other at a 
particular pixel location. Thus any desired image can be produced by 
applying a voltage difference across the particular row busbars 21 and 
column busbars 26 that define image pixels 29 at which light needs to be 
emitted to form the image. 
Knob 12 is engaged on a base member 31 which is bonded to the front surface 
32 of transparent cover pate 28. In an alternate construction the base 
member may be secured to a second transparent cover plate which is 
overlaid on the original transparent cover plate of the flat panel 
display. Referring now to FIGS. 5 and 6 in conjunction, the base member 31 
of this example is annular and extends into an opening 33 in the base of 
the knob 12, the opening being of larger diameter than the base member. 
The base member has a circular groove 34 which extends around the member 
within opening 33. A resilient clasp 40 formed of spring steel or the like 
has a generally elliptical configuration and has a first end 35A that is 
secured to the wall of opening 33. A flattened opposite end 35B of the 
clasp 40 extends into a slot 36 in the portion of knob 12 that encircles 
opening 33. The end of base member 31 is beveled and forces a temporary 
expansion of the clasp 40 as the knob 12 is being forced onto the base 
member after which the clasp seats in groove 34 and retains the knob on 
the base member. The knob 12 can be easily removed from the base member 31 
by forcing end 35B of clasp 40 inward at slot 36 with the tip of a 
screwdriver or similar tool. This expands the clasp 40 and forces it out 
of groove 34. The clasp 40 and groove 34 may be replaced with other 
structure for engaging the knob on the base member examples of which will 
be hereinafter described. 
A trace 37 of electrically resistive material is bonded to the front 
surface 32 of transparent cover plate 28 within the base member 31 and is 
of circular configuration except that the resistor trace is discontinuous 
at at one location and thus has spaced apart ends 38, the once being 
centered on the axis of rotation 39 of knob 12. A pair of spaced apart 
electrically conductive traces 41 extend along front surface 32 of cover 
plate 28 from ends 38 of the resistor trace 37 to a connector 42, shown in 
FIG. 1, at an edge of the flat panel display 16. Connector 42 provides for 
connection of the conductive traces 41 to a voltage source 43 shown in 
FIG. 2B. 
Referring again to FIGS. 5 and 6, the connection of the ends 38 of resistor 
trace 37 to a voltage source creates a progressive voltage drop along the 
trace. To provide a selectable output voltage, a resilient and conductive 
dual wiper contact 45 extends from knob 12 within the knob opening 33. 
Contact 45 has a first wiper arm 47 positioned to contact resistor 37 and 
to travel along the trace as the knob is turned. A second wiper arm 48 of 
contact 45 extends into contact with a conductive pad 49 which is bonded 
to the front surface 32 of cover plate 28. Another conductive trace 51 
extends along the front surface of cover plate 28, in parallel 
relationship with traces 41 to connect pad 49 with the previously 
described connector 42 thereby enabling transmission of an operator 
selected voltage to the circuit which the potentiometer 11 controls. 
The conductive traces 41 and 51 which extend along the cover plate 28 
within the image display area may be formed of transparent conductive 
material, such as indium tin oxide, to avoid interference with viewing of 
the displayed graphics. 
FIG. 7 depicts a modification of the potentiometer 11a in which the base 
member 31a is a disk of insulative material and in which the resistor 
trace 37a is bonded to the base member rather than being directly bonded 
to the cover plate 28a. Potentiometer 11a may otherwise be similar to the 
previously described embodiment. 
FIG. 8 depicts another modification of the potentiometer 11b in which the 
conductive traces 41b which connect with the ends of the resistor trace 
37b and the trace 51b which connects with wiper contact 45b extend along 
the back surface 52 of transparent cover plate 28b. This protects the 
traces 41b, 51b from abrasion. Connector pins 53 extend through the cover 
plate 28b to connect the traces 41b and 51b in the previously described 
manner with components that are within the base member 31b. 
The knob 12b of this embodiment has a tapered side surface 54 that is 
broadest at its base. The snap engagement of knob 12b onto base member 31b 
is made by forcing the base of the knob into a conforming annular recess 
56 in the inner surface of the base member. The dual wiper 45b of this 
embodiment has a first wiper arm 47b that rides on the resistor trace 37b 
and a second arm 57 which contacts and travels along a circular trace 58 
of conductive material which is coaxial with the resistor trace and which 
is bonded to the cover plate 28b. One of the connector pins 53b extends 
through cover plate 28b to connect the circular trace 58 with conductive 
trace 51b. 
Referring jointly to FIGS. 4 and 8, disposition of the conductive traces 
41b, 51b at the back surface 52 of the transparent cover plate 28b in the 
above described manner makes it possible to form such traces of 
non-transparent material, such as copper or aluminum for example, without 
creating any noticeable disruption in images which are viewed through the 
cover plate. Referring to FIG. 4 in particular, this may be accomplished 
by positioning the traces 41b and 51b to extend in parallel relationship 
with the rows of image pixels 29 at locations which are between two rows 
of pixels. 
In the modification of the potentiometer 11c which is shown in FIG. 9, the 
turnable knob 12c does not snap engage on the base member 31c as in the 
previously described embodiments. The knob 12c simply fits onto a circular 
base member 31c and is held in place by a turnable rod 61 which extends 
along the axis of rotation of the knob. A flanged end 63 of rod 61 extends 
out of the base of the knob 12c. A set screw 64 extends radially within 
the knob and engages rod 61. A housing 68 encircles and overlaps the 
flanged end 63 of the rod 61 and is bonded to the face of cover plate 28c 
in order to hold the knob 12c on base member 31c. The rod 61 can turn 
freely on the base member 31c but is held in position by the housing 68 
and flange. An annular stop 62, formed of a material having a low 
coefficient of friction, such as Teflon for example, extends between the 
peripheral region of the base of knob 12c and cover plate 28c. The stop 62 
prevents breakage of the glass cover plate by flange 63 which might 
otherwise occur if an operator should exert a strong lateral force on the 
knob 12c. The potentiometer 11c is otherwise similar to the previously 
described embodiment of FIG. 8. 
The previously described embodiments of the invention each have at least 
one wiper contact which bears against and travels along a resistor trace. 
FIG. 10 depicts a form of wiper contact which can prolong the life of the 
control devices by reducing abrasion of the resistor traces. A small 
spherical ball 69 formed of electrically conductive material is disposed 
between each wiper contact 47d or 57d that travels along a resistor trace 
37d or conductive trace 58d. Small cylindrical rollers can be substituted 
for the balls 69. In this example, the wiper contacts 47d and 57d are 
opposite ends of a conductive leaf spring 71 which bear against the balls 
69 and which is secured at its center to the knob 12d. Wiper contacts 47d 
and 57d extend into housings 72 in the base of knob 12d which hold the 
balls 69 at the traces 37d and 58d. 
The need for housings 72 can be eliminated if, as shown in FIG. 11, the 
resistive or conductive trace 73 is made sufficiently thick to enable a 
circular groove 74 to be formed in the trace and the ball 69 is seated in 
the groove. A similar result is obtained if, as shown in FIG. 12, the 
trace 73 is a thin lining in a groove 76 formed in a circular base 77 
which is bonded to the cover plate 28, the base being formed of insulative 
material. 
Automatic cleaning of the trace 73 can be provided for by a brush 75, 
formed of mildly abrasive flexible fibers, which extends from the wiper 
arm 47d to trace 73 and which bears against the exposed surface of the 
trace as the arm travels along the trace. 
The invention is highly advantageous when embodied in a turnable knob type 
of circuit control device of the kind which does not revert to an initial 
setting after each full revolution of the knob but instead proceeds to 
progressively higher settings throughout two or more revolutions of the 
knob. The invention enables display of progressively higher ranges of 
output signal values around the perimeter of the knob during successive 
revolutions of the knob. FIGS. 13, 14 and 15 depict a multi-turn 
potentiometer of this kind. 
Referring jointly to FIGS. 13, 14 and 15, the potentiometer 11e has an 
annular base member 31e bonded to the front surface of a flat panel 
display cover plate 28e and a turnable knob 12e which is snap engaged on 
the base member in the previously described manner. The knob 12e is 
typically longer than in the previously described embodiments and has a 
hollow interior 78 that is open at at the base-of the knob. A threaded rod 
79 within the knob 12e extends along the axis of rotation of the knob and 
has a pilot projection 81 at one end that seats in a bearing 82 that is 
bonded to the front surface of cover plate 28e. The other end 83 of rod 79 
extends into the material of the knob 12e at the distal end of the knob 
and is bonded thereto thereby causing the rod to turn with the knob. 
Base member 31e has a cylindrical sleeve portion 84 which extends up into 
the interior 78 of knob 12e and which encircles rod 79 in spaced apart 
relationship therewith. A trace or strip of resistive material 86 is 
bonded to the inside surface of the sleeve portion 84 and extends in 
parallel relationship with the rod 79. An internally threaded collar 88 
encircles rod 79 and engages the threads of the rod. An arm 89 extends 
radially from collar 88 into a longitudinal slot 91 in sleeve portion 84 
of the base member 31e. This prevents rotation of the collar 88 and causes 
it to travel along rod 79 when the knob 12e is turned, the direction of 
travel being determined by the direction of the turning of the knob. 
Another radially directed arm 92 extends from collar 88 and carries a wiper 
contact 93 which bears against and travels along the resistive trace 86. 
Conductors 94 embedded within the sleeve portion 84 of base member 31e 
extend up from the surface of cover plate 28e to apply differing voltages 
to the opposite ends of the resistive trace 86. Rod 79 and collar 88 
including arm 92 are formed of electrical conductor enabling the output 
voltage of the potentiometer lie to be picked up by another wiper contact 
96 which is bonded to the front surface of cover plate 28e. 
Provided that the rod 79 and resistive trace 86 are of sufficient length, 
the potentiometer lie outputs a continuously increasing or continuously 
decreasing voltage signal as the knob 12e is revolved through a plurality 
of full revolutions. Referring again to FIG. 1, the flat panel display 
controller 17 can be conditioned to change the calibration marks 13 each 
time a full revolution of the knob is completed in order to conform the 
marks with the current range of output voltages. 
Any of the previously described potentiometers can be used as a variable 
resistor if voltage is applied to only one end of the resistive trace. 
Abrasion over a period of time can adversely affect output signal accuracy 
in potentiometers which include a moving wiper contact that rubs against a 
resistor. The function of a potentiometer can be realized without making 
use of such components. For example, with reference to FIGS. 16 and 17 in 
conjunction, a radio frequency circuit 97 can be used to sense the setting 
of a turnable knob 12f and to track angular motion of the knob. 
The embodiment of FIGS. 16 and 17 again has a turnable knob 12f snap 
engaged on an annular base member 31f which is bonded to the transparent 
cover plate 28f of a flat panel display 16f within the image display area 
in the manner previously described. A small integrated circuit board or 
chip 98 is adhered to the surface of cover plate 28f within the base 
member 31f. Chip 98 includes two electrical oscillators 99 and 101, shown 
in FIG. 18, which may be of any of the known types such as Colpitts 
oscillators for example. The chip 98 also includes two buffer amplifiers 
102 and 103 and two capacitors 104 and 106 which are the capacitive 
components of the resonant circuits of the oscillators 99 and 101. 
Referring again to FIGS. 16 and 17, the inductive component of the 
resonant circuit of each oscillator is one of a pair of inductance coils 
107 and 108 which are within the base member 31f. Coils 107 and 108 are 
preferably spiral shaped conductive traces bonded to the surface of cover 
plate 28f. 
Coils 107 and 108 are at different locations relative to the axis of 
rotation of knob 12f and are preferably situated at locations which are 
90.degree. apart relative to the axis of rotation. A body 109 of 
electrically conductive metal, which is preferably ferromagnetic material, 
is secured to the base of knob 12f at a location which is offset from the 
axis of rotation of the knob. 
Referring jointly to FIGS. 17 and 18, the resonant frequencies of both 
oscillators 99 and 101 are affected by the presence of the conductive body 
109 in close proximity to the coils 107 and 108 and the frequency of each 
of the oscillators changes as the body 109 becomes closer or further away 
from the coil 107 or 108 of the oscillator. The frequency shifting effect 
on the two oscillators 99 and 101 is different at any given time as the 
two coils 107 and 108 are at different locations along the path of 
revolution of the body 109. Consequently the ratio of the frequencies of 
the two oscillators 99 and 101 varies as knob 12f is turned and is 
different at each angular setting of the knob. This allows a 
microprocessor 111 to identify the rotational position of knob 12f at any 
given time and to output a control signal which is a function of the 
angular position of the knob. 
Referring to FIG. 18 in particular, the resonant circuit of oscillator 99 
is coupled to the input of a counter 112 through buffer amplifier 102, a 
capacitor 113 and a first conductor 114 which extends between the location 
of the oscillators and the location of the microprocessor 111. The 
resonant circuit of the other oscillator 101 is coupled to the input of 
another counter 116 through the other buffer amplifier 103, another 
capacitor 117 and a second conductor 118 that extends to the location of 
the microprocessor 111. 
Each counter 112 and 116 counts the number of radio frequency cycles that 
are generated by the associated oscillator 99 or 101 during successive 
time periods of fixed duration. The accumulated counts are transferred to 
shift registers 119 and 121 at the end of each such time period and the 
counters are reset to a count of zero by the microprocessor 111. FIG. 18A 
depicts the microprocessor program in flowchart form. Referring jointly to 
FIGS. 18 and 18A, microprocessor 111 repetitively reads the shift 
registers 119 and 121, computes the ratio of the frequencies of the two 
oscillators, and consults a look-up table which is configured within the 
microprocessor to determine the control signal magnitude that should be 
outputted at the current angular setting of the turnable knob. The current 
control signal value is outputted in digital form if the controlled 
electrical circuit responds to digital control signals or is delivered 
through a digital to analog converter 122 if the controlled circuit 
responds to a variable voltage type of control signal. 
Capacitors 113 and 117 are present in the above described circuit to enable 
transmission of the high frequency signals and also DC operating current 
on the single pair of conductors 114 and 118 that extend between the 
location of the oscillators 99 and 101 and the location of the 
microprocessor 111 which may be at the edge region of the flat panel 
display. The conductors 114 and 118 each connect with a separate one of 
the terminals of a DC power supply 124 through a separate one of a pair of 
inductance coils 126. A capacitor 127 is connected across the DC power 
supply terminals. This forms a filter which allows DC current to be 
transmitted to conductors 114 and 118 and which isolates the power supply 
from the high frequency signals. The other ends of conductors 114 and 118 
connect with the DC power inputs of both oscillators 99 and 101 through 
separate ones of another pair of inductance coils 128 and another 
capacitor 129 is connected between the positive and negative terminals of 
the oscillators. This keeps the high frequency signals out of the 
oscillator power terminals. Capacitors 113 and 117 isolate the buffer 
amplifiers from the DC current. 
In FIG. 18 components which are above the dashed line 131 are situated 
inside the turnable knob and base member assembly of the control device 
and components which are below the dashed line are in the edge region of 
the flat panel display. 
Referring again to FIGS. 16 and 17, the radio frequency circuit which is 
within the base member 31f can be adversely influenced by external 
influences which alter the inductance and/or capacitance of the resonant 
circuits or create circuit noise. Under some circumstances the operator's 
fingers can have an effect of this kind. It preferable that the region 
inside base member 31f be isolated from influences of this kind by a 
lining 132 Mu metal shielding. The lining 132 substantially encloses the 
region in which the radio frequency circuit components are situated. The 
driver circuits within the flat panel display 16f itself can under some 
circumstances adversely interact with the components on the cover plate 
28f. This can be prevented by disposing a thin layer 133 of electrical 
conductor between the cover plate 28f and the other layers of the flat 
panel display 16f. Insulation 134 isolates the signal and power conductors 
114 and 118 from the conductive layer 133. 
Referring to FIG. 19, the integrated circuit chip 98 and coils 107 and 108 
can alternately be situated at the back surface of the cover plate 28f at 
a location behind the knob 12f. As shown in FIG. 20, the chip 98 and coils 
107 and 108 can also be at the back surface of the flat panel display 16f 
if the display is sufficiently thin to enable interaction with the body 
109 of conductive material within the turnable knob and if there are no 
solid conductive layers within the display. The control devices of FIGS. 
19 and 20 may otherwise be similar to the control device of FIGS. 16 to 
18. 
Referring to FIG. 21, circuit components such as the oscillators 99 and 
101, buffer amplifiers 102, 103, inductance coils 128 and capacitors 113 
and 117 can also be embedded within the turnable knob 12g. The oscillator 
coils 107 and 108 in this case are bonded to the knob 12g within an 
opening 136 in the knob that faces toward the transparent cover plate 28g 
and are positioned, relative to the axis of rotation of the knob, as 
previously described. The circuit components which are within the knob 12g 
are connected to the DC power and radio frequency signal conductors 114 
and 118 that extend along the cover plate 28g through a pair of wiper 
contacts 137 and 138 which extend from the knob within opening 136. 
Contact 137 bears against a first beveled conductive ring 139 that is 
bonded to the surface of the cover plate 28g and which is centered on the 
axis of rotation of the knob 12g. Contact 138 bears against a second 
similar ring 141 which overlays ring 139 and which is electrically 
isolated therefrom by an annular band 142 of insulation. Power and signal 
conductor 114 is connected to ring 139 and conductor 118 connects to ring 
141. The body 109 of conductive material that varies the frequencies of 
the oscillators 99 and 101 is secured to the second ring 141 by adhesive 
or other means at a location which is offset from the axis of rotation of 
the knob 12g. 
Rings 139 and 141 may be replaced with a pair of annular bands 143 which 
are bonded to the front surface of cover plate 28g as shown in FIGS. 22 
and 22A. The bands 143 are centered on the axis of rotation of the knob 
12g and are of different diameter in order to be electrically isolated 
from each other. The wiper contacts 137 and 138 which extend from knob 12g 
are repositioned to bear against the bands 143. The conductive body 109 is 
bonded to cover glass 28g between the outermost band 143 and base member 
31g. The control device of FIGS. 22 and 22A may otherwise be similar to 
the control device of FIG. 21. 
The rotational position of a knob or the like can be sensed by still other 
means. Referring jointly to FIGS. 23 and 24, a specialized form of 
capacitor 144 may be used for this purpose. The control device 11h of 
FIGS. 23 and 24 has a turnable knob 12h snap engaged on an annular base 
member 31 which is bonded to the front surface of the transparent cover 
plate 28h of a flat panel display 16h which components may be similar to 
the corresponding components of the previously described embodiments. An 
oscillator 146 circuit board is bonded to the face of cover plate 28h 
within the base member 31h. The inductive component of the resonant 
circuit of oscillator 146 is a spiral shaped coil 147 of conductive metal 
bonded to the surface of cover plate 28h within the base member 31h. 
Capacitor 144 is the capacitive component of the resonant circuit and is 
formed by two discontinuous circular traces 148 and 149 of electrically 
conductive material that are bonded to the front surface of the cover 
plate 28h. The traces 148 and 149 are each centered on the axis of 
rotation of knob 12h and are of different diameter in order to be spaced 
apart from each other. Each of the traces 148 and 149 has a width which is 
broadest at one end of the trace and which progressively diminishes along 
the length of the trace. The broadest ends of both traces 148 and 149 are 
adjacent to each other. 
A conductive plate 151 is secured to the base of the turnable knob 12h and 
spans traces 148 and 149 in spaced apart relationship therewith, the plate 
having a width in the direction of travel of the plate that is 
substantially smaller than the length of the traces. 
Traces 148, 149 and plate 151 jointly form a three plate capacitor the 
capacitance of which progressively decreases or increases as knob 12h is 
turned to travel the plate along the traces. This progressively changes 
the resonant frequency of oscillator 146 and each rotational position of 
the knob 12h is characterized by a different specific frequency that is 
used to identify the position and to track rotary motion of the knob 12h. 
Referring to FIG. 25, a circuit junction 152 between capacitor 144 and 
inductance coil 147 is coupled to a frequency cycle counter 153 through a 
buffer amplifier 154 which may be situated at the oscillator circuit 
board. Referring jointly to FIGS. 25 and 25A, a microprocessor 111, which 
may be within the marginal region of the flat panel display, cyclically 
reads the accumulated count in counter 153 and resets the counter in order 
to detect the current resonant frequency of the oscillator 146. The 
microprocessor 111 outputs a digital control signal which has a value that 
changes in response to changes of the frequency caused by changes in the 
angular setting of the turnable knob. The control signal may be delivered 
through a digital to analog converter 156 if the controlled electrical 
circuit is of a type that responds to variable voltage control signals. 
The microprocessor 111, counter 153 and a DC power supply 157 for the 
oscillator 146 are situated in the marginal region of the flat panel 
display. 
The oscillator 146 of this example is of the harmonic type which has a 
resonant circuit formed by capacitor 144 and coil 147. The oscillator can 
also be of the relaxation type in which case coil 147 is replaced with a 
resistor. 
In a modified form of the capacitive control device one of the conductive 
traces of the capacitor 144 is replaced with a relatively thin circular 
band 155 of electrical conductor of uniform width as shown in FIG. 26. The 
movable capacitor plate 151 carries a wiper contact 158 which contacts and 
travels along the band 157. The control device of FIG. 26 may otherwise be 
similar to the control device of FIGS. 23 to 25. 
Rotary motion of the control device knob can also be tracked and settings 
identified by photoelectric means. Referring jointly to FIGS. 27, 28 and 
29, a control device 11j of this kind may have a turnable knob 12j snap 
engaged on an annular base member 31j at the face of a flat panel display 
16j which components may be similar to those of previously described 
embodiments. The knob 12j has an interior chamber 159 which opens at the 
base of the knob and a mirror 161 is secured to the knob within the 
chamber. Mirror 161 is spaced outward from base member 31j and oriented to 
return light which is received from the region of the base member back 
towards that region. 
A layer 162 of opaque material is bonded to the front surface of the 
transparent cover plate 28j within the base member 31j to prevent entry of 
external light into chamber 159. This objective can be met without the 
opaque layer 162 if the flat panel display 16j is conditioned to always 
present a solid black image at the location of the base member 31j 
regardless of what is being displayed at other locations. 
An LED (light emitting diode) 163 or other light source is secured to the 
center of layer 162 to direct light towards mirror 161. Returned light is 
detected by two phototransistors 164A and 164B or other light sensors 
which are secured to layer 162 at opposite sides of LED 163, the 
photodiodes being equidistant from the axis of rotation of knob 12j. The 
angular spacing of the phototransistors 164A and 164B from each other, 
relative to the axis of rotation of the knob is less than 180.degree.. 
Light in passage from LED 163 to the phototransistors 164 is modulated by 
an opaque disk 166 which extends across chamber 159 at a location between 
the mirror 161 and phototransistors 164. Disk 166 has an opening 167 or 
transparent region at its center to provide a light path from LED 163 to 
the mirror. The disk also has an annular array of uniformly spaced apart 
slots 168 or transparent zones through which reflected light is received 
by phototransistors 164. Slots 168 are shaped and positioned to create a 
quadrature code of the kind known to the art which enables a digital data 
processor to track rotary motion of a knob around a series of angular 
settings and to output a signal which is indicative of the current 
setting. 
In this example there are four slots 168 each of which extends along 
45.degree. of arc relative to the axis of rotation and which are separated 
from each other by opaque regions of the disk 166 of similar arcuate 
length. Phototransistors 164A and 164B are positioned to create the 
response pattern which is depicted diagramatically in FIG. 29A and which 
enables a digital data processor to distinguish between 16 different 
positions of the knob 12j. At a first position, shown in FIG. 29, both 
phototransistors 164A and 164B are illuminated. When the knob is turned 
clockwise 22.5.degree., only phototransistor 164B is illuminated. Further 
turning by the same amount blocks light from both phototransistors 164A 
and 164B. Upon further turning by the same amount, only phototransistor 
164A is illuminated. This pattern is continually repeated as clockwise 
turning of the knob 12j is continued. Reversed turning of the knob 12j 
creates a reversed pattern of phototransistor illuminations. 
Referring now to FIGS. 30 and 30A, each phototransistor 164 is connected 
between a separate port of a microprocessor 111 and system ground in 
series with separate resistors 165. This causes the voltage at each such 
microprocessor port to change from a high status to a low status each time 
that a pulse of light is received by the phototransistor that is connected 
to the port. As depicted in FIG. 30A, the microprocessor tracks turning of 
the knob by counting such changes of status in an additive and subtractive 
manner. Prior to each incrementing of the count the program executes a 
direction subroutine, depicted in FIG. 30B, to determine if the knob 
motion is clockwise or counter clockwise. Referring jointly to FIGS. 29A 
and 30B, the four possible combinations of the status of the two 
phototransistors 164A and 164B (sensor A and sensor B) can be represented 
as 00, 01, 10 and 11. If the status combination changes from 00 to 01 or 
from 01 to 11 or from 10 to 00 or from 11 to 10 then the knob motion is 
counter clockwise and the program increments the count in a subtractive 
manner. Any other change in the status combination is indicative of 
clockwise knob motion and the count is incremented in an additive manner. 
Referring again to FIGS. 27 to 29, the resolution of the control device 12j 
can be increased by providing disk 166 with a greater number of the slots 
168. 
LED 163 is energized by a DC power supply 169 which may be located in the 
marginal region of the flat panel display. 
Referring now to FIGS. 32 and 33, LED 163 can be encircled by an opaque 
cylindrical light barrier 173 which extends from the opaque layer 162 up 
into a slot 174 in the light modulating disk 166 to optically isolate the 
two phototransistors 164 from each other. A similar result can be effected 
by providing an opaque housing 176 around each phototransistor 164 as is 
shown in FIGS. 34 and 35. Each housing 176 has a thin slot 177 which faces 
the light modulating disk 166 to admit pulses of light into the housing. 
The slotted housings 176 have the further beneficial effect of causing the 
phototransistors 164 to receive light from only one of the slots 168 at 
any given time. 
As shown in FIG. 31A, only one phototransistor 164, photodiode or the like 
is needed if the light modulating disk 166 of FIGS. 27 and 29 is replaced 
with a disk 171 of the form shown in FIG. 31. Instead of slots disk 171 
has an annular band 170, centered on the axis of rotation, that is of 
maximum light transmissivity at one location and which becomes 
progressively less light transmissive at successive other locations around 
the band. The output of the single phototransistor is then a function of 
the angular orientation of the knob. 
The control device of FIGS. 27 to 35 uses an LED 163 and phototransistors 
164 which are separate components separately secured to the opaque layer 
162. Referring now to FIGS. 36 and 37, the control device and other 
control devices to be hereinafter described can be more economically 
manufactured in large numbers by integrating these components into a 
single photoelectric chip or wafer 178. For this purpose, an LED 163 and 
phototransistor 164 are bonded to a flat base 179 and are spaced apart 
thereon. Both the LED 163 and the phototransistor 164 have one of a pair 
of lenses 181 bonded thereto, the lenses being formed to focus light from 
the LED at a point located a predetermined distance away and to focus 
light which is reflected back from that point at the phototransistor 164. 
FIGS. 38 and 39 depict another electrical circuit control device 11k in 
which a bank of three potentiometers 181, 182 and 183 are secured to the 
transparent cover plate 28k of a flat panel display 16k within the image 
display area. The potentiometers 181, 182 and 183 each have a turnable 
knob, 12k, 121, and 12m respectively, snap engaged on annular base 
members, 31k, 31l and 31m respectively in the previously described manner. 
The base members 31k, 31l and 31m are spaced apart and each is bonded to 
the cover plate 28k by an adhesive. Each of the potentiometers 181, 182 
and 183 uses one of the above described photoelectric wafers 178 to sense 
changes in the rotational position of the knob of the potentiometer to 
enable synthesis of a variable control signal for a controlled electrical 
circuit. 
The knob 12k of the first potentiometer 181 has an interior chamber 184 and 
a mirrored disk 186 is bonded to the knob within the chamber. Disk 186 
parallel in parallel relationship with cover plate 28k, is spaced apart 
from the cover plate and is centered on the axis of rotation of knob 12k. 
A circular band 187 of light reflecting material is present on the surface 
of disk 186 that faces cover plate 28k, the band being centered on the 
axis of rotation of the disk. The density of the reflective material and 
thus the reflectivity of the material progressively changes from a minimum 
to a maximum at successive locations around the band, the zone of minimum 
light reflection being adjacent to the zone of maximum light reflection. 
A photoelectric wafer 178 of the previously described kind is embedded in 
the front surface of cover plate 28k at a location at which the focal 
point of the light beam that is emitted by the wafer is at the band 187 of 
light reflective material. Thus light is reflected back to the wafer 178 
and the reflected light has an intensity that increases as knob 12k is 
turned in one direction and decreases when the knob is turned in the 
opposite direction. This enables detection of the direction of turning of 
the knob and detection of the current angular orientation of the knob in 
order to produce a control signal that is indicative of the position of 
the knob. The electrical circuit which is coupled to wafer 178 for this 
purpose may be similar to that previously described with reference to FIG. 
30A. 
In the second potentiometer 182 of control device 11k an opaque mask 188 is 
disposed between the base member 31l and cover plate 28k so that light 
which is produced within the flat panel display 16k will not affect the 
output of the photoelectric wafer 178. The mask 188 has an opening 189 
which overlays the wafer 178 to enable passage of light between the wafer 
and the mirrored disk 186. The lenses of the photoelectric wafer 178 of 
potentiometer 182 have a shorter focal length than the corresponding 
components of the first potentiometer 181. Thus the mirrored disk 186 of 
the second potentiometer 182 is closer to the wafer 178. Except as 
described above, the second potentiometer 182 is similar to the first 
potentiometer 181. 
In the third potentiometer 183 of control device 11k, the photoelectric 
wafer 178 is embedded in the back surface of the transparent cover plate 
28k in position to view the mirrored disk 186 through an opaque tube 191 
which extends outward from cover plate 28k within the base member 31m and 
knob 12m. If the disk 186 is beyond the focal point of the lens of wafer 
178 a supplementary lens 192 situated at the outer end of tube 191 focuses 
the light at the disk. If cover plate 28k is formed of glass as in this 
example, the base member 31m can be unitized with the cover plate by 
forming the base member of glass and by bonding it to the cover plate with 
solder glass. 
The third potentiometer 183 may otherwise be similar to the first 
potentiometer 181. 
Referring to FIGS. 40 and 41 in conjunction, a magnet 193 and a pair of 
analog Hall effect sensors 194-1 and 194-2 may also be used to sense 
changes in the angular setting of a turnable knob 12p and thereby enable 
generation of control signals that vary in response to turning of the 
knob. The control device 11p may be mechanically identical to the radio 
frequency embodiment previously described with respect to FIGS. 16 and 17 
except insofar as the Hall effect sensors are substituted for the two 
oscillator coils 107 and 108 of the previously described embodiment and 
the conductive body 109 of the previously described embodiment is replaced 
with magnet 193. 
The electrical resistance of each Hall effect sensor 194 decreases as the 
magnet 193 approaches the sensor during turning of the knob 12p and 
increases as the magnet recedes from the sensor. Referring to FIG. 42, the 
first Hall effect sensor 194-1 is connected across the positive and 
negative terminals of a DC voltage source 196 in series relationship with 
a first resistor 197 and the second sensor is connected across the 
terminals in series with a second resistor 198. The first sensor 194-1 and 
resistor 197 form a first voltage divider in which the voltage at a 
circuit junction 199 between the sensor and resistor changes when the 
resistance of the sensor changes. The other sensor 194-2 and the second 
resistor 198 form a second voltage divider having a similar circuit 
junction 201 at which the voltage changes when the resistance of the 
sensor changes. 
Referring to FIGS. 40 and 41 in conjunction, the two Hall effect sensors 
194 of this example of the invention are positioned at locations which are 
90.degree. apart relative to the axis of rotation of knob 12p. The angular 
spacing of the two sensors may have other values in other examples of the 
invention. The first sensor 194-1, also identified as sensor 1 in the 
drawings, is in this example situated at the 0.degree. angular position of 
the knob 12p. The second sensor 194-2, also identified as sensor 2 in the 
drawings, is at the 270.degree. position and thus the output signals of 
the two sensors are 90.degree. out of phase as may be seen in FIG. 43 
wherein curved line 1A represents the varying output signal of the first 
sensor and curved line 2A represents the output signal of the second 
sensor. 
Referring jointly to FIGS. 40 to 43, the two voltage values which are 
present at circuit junctions 199 and 201 are used to identify the 
rotational orientation of knob 12p. Each circuit junction 199 and 201 is 
coupled to a separate port of a microprocessor 111 through a separate one 
of a pair of buffer amplifiers 202 and a separate one of a pair of analog 
to digital signal converters 203. The microprocessor 111 converts the 
output signal 1A of the first sensor 194-1 to a control signal which 
varies as a function of the angular position of knob 12p. The control 
signal may be caused to vary in a linear manner or to follow some other 
desired response curve by establishing an internal lookup table in the 
microprocessor 111 which contains assigned values for the control signal 
at each angular setting of the knob 12p. The microprocessor 111 replaces 
the actual signal values that are produced at circuit junction 199 with 
the assigned values, this method of producing a desired response curve 
being hereinafter described in more detail. 
As depicted in FIG. 43, the output signal 1A of the first sensor 194-1 has 
a different magnitude at each position of the knob 12p as it is turned 
from the 0.degree. position to the 180.degree. position. The signal 1A 
value then returns through the same range of signal values as the knob 12p 
is turned further in the same direction from the 180.degree. position to 
the 360.degree. (0.degree.) position. Microprocessor 111 uses the output 
signal 2A from the second sensor 194-2 to determine if a first output 
signal 1A of a particular magnitude represents a position in the 0.degree. 
to 180.degree. range or a position which is greater than 180.degree.. The 
second sensor output signal 2A has a particular value, designated as K in 
FIG. 43, when the knob 12p is at the 180.degree. position. Signal 2A is 
smaller than K when the knob 12p is between the 0.degree. and 180.degree. 
positions (at which time magnet 193 is at the right half of FIG. 41) and 
is greater than K when the knob is in between the 180.degree. and 
360.degree. positions (at which time magnet 193 is at the left half of 
FIG. 41). As depicted in flowchart form in FIG. 42A, the microprocessor 
consults a lookup table to translate the current value of signal 1A into 
an assigned value representing the current angular position of the knob 
within a range of 0.degree. and 180.degree. which assigned value is 
designated by letter D in FIG. 42A. If the second sensor signal 2A is 
greater than K at that time, the microprocessor outputs a control signal 
equal to 360.degree. minus D. Otherwise, the outputted control signal is 
equal to D itself. 
Referring to FIG. 43B, a greater number of the Hall effect sensors may be 
present in order to increase precision in the tracking of motion of the 
knob 12p. In this example three analog Hall effect sensors 194-1, 194-2 
and 194-3 are situated at angular intervals of 120.degree. around the axis 
of rotation of the knob 12p, the location of sensor 194-1 again being the 
0.degree. position of the knob 12p, sensor 194-2 being at the 120.degree. 
position and sensor 194-3 being at the 240.degree. position. The physical 
structure of the control device 11q may otherwise be similar to that of 
the previously described Hall effect control device 119 of FIGS. 40 and 
41. 
Referring to FIG. 43C, the electrical circuit of the control device 11q may 
also be similar to that previously described with reference to FIG. 42 
except insofar as the third sensor 194-3 is connected to the DC voltage 
source 196 and to microprocessor 111 in a manner similar to the 
connections of the first two sensors therewith. Thus the third sensor 
194-3 is connected across the positive and negative terminals of DC 
voltage source 196 in series relationship with a third resistor 198-1. A 
circuit junction 199-1 between the third sensor 194-3 and third resistor 
198-1 transmits the output signal of the third sensor to the 
microprocessor 111 through another buffer amplifier 202-1 and another 
analog to digital signal converter 203-1. 
Referring jointly to FIGS. 43D and 41, the microprocessor 111 is programmed 
to monitor the strength of the output signals of each of the sensors 
194-1, 194-2 and 194-3 which sensors in this example have equal 
sensitivities. If one of the signals is strongest and the other two are 
equal to each other than the magnet 193 is at the location of the sensor 
with the strongest signal. At other times the magnet 193 is between the 
locations of the two sensors which are producing the strongest signals. 
The microprocessor 111 detects the exact location between the sources of 
the two strongest signals by computing the ratio of those two signals 
which ratio progressively changes as the magnet moves away from one such 
source and towards the other. The ratio typically does not change in a 
linear manner. The microprocessor 111 corrects for this by referring to an 
internal look up table in which each ratio value is correlated with the 
actual angular position of the knob 12p that produces that ratio value. 
The microprocessor 111 or other data processor can be programmed to revert 
to the two sensor mode of operation previously described with reference to 
FIG. 42A in the event of failure of one of the three sensors 194-1, 194-2 
or 194-3. 
Upon power-up, both the control device 11p of FIGS. 40 to 42 and the 
control device 11q of FIG. 43B can detect a change in the setting of the 
knob that has been made during a period when the power was off. 
Referring jointly to FIGS. 44 and 45, the control devices which have been 
previously described have a base member, such as base member 437, which is 
bonded to the front surface of the transparent cover plate 316 of the flat 
panel display 317. It can be advantageous if the base member 437 has one 
or more protrusions 438 which extend into or through the cover plate 316 
at conforming openings 439 in the plate. This resists lateral forces on 
the control devices that might tend to detach them from the display. The 
protrusions 438 can be formed of metal to provide the hereinbefore 
described electrical connections to conductors at the back surface of 
cover plate 316. In instances where more than one control device is to be 
bonded to the same flat panel display 317, the bases 437 can each have 
protrusions 438 which are arranged in a different pattern and/or which 
have different shapes to assure that each control device is bonded to the 
display 317 at the correct location for the particular control device. 
Referring to FIG. 46, rotary movement of the knob 441 of a circuit control 
device which is secured to the face of a flat panel display 317 can be 
tracked by a magnetic pad 439 of the known design which is bonded to the 
back surface of the display. The control devices 442 of this embodiment 
may be similar to any of the previously described rotary knob control 
devices except that the electronic components in the knobs and knob bases 
are not needed. In the present embodiment a small magnet 443 is embedded 
in the knob 441 at a location which is offset from the axis of rotation of 
the knob. Movement of the magnet 443 is sensed by the pad 439 and a signal 
indicative of the current rotational orientation of the knob 441 is 
produced by a magnetic pad position signal generator 444 which may be of 
the known circuit configuration. The microprocessor 111 outputs a control 
signal to the controlled circuit 446 in the. previously described manner 
wherein the control signal has a magnitude determined by the rotational 
orientation of knob 441. The microprocessor 111 also causes the flat panel 
display controller 17 to provide graphics 447 at the flat panel display 
317 that are indicative of the current setting of the control device. 
In each of the above described circuit control devices both the knob and 
base member are situated in front of the supporting panel and electrical 
components of the devices are contained within the knob and base at the 
front of the panel. The described knob motion sensing means enable the 
devices to have a compact configuration that is conducive to the situating 
of the devices within the image display area of a flat panel display. The 
control device construction also facilitates maintenance and repairs as 
all components are accessible at the front of the supporting panel by 
simply detaching the knob from the base member. Embodiments of the 
invention in which electrical components are embedded in or are carried by 
the knob itself, such as the control device of FIGS. 21 and 22 for 
example, can be quickly and easily repaired by someone who is unskilled in 
electrical repairs by simply removing the knob and replacing it with a new 
one. 
In the previously described circuit control devices rotary movement of the 
knob between a series of different settings produces a control signal 
having a value that progressively changes during the course of the knob 
movement. In some of these control devices the original control signal 
value at successive settings of the knob does not change in a linear 
manner nor follow any of the other response curves, such as a logarithmic 
curve for example, that are customary in control devices. This effect 
results from the geometry of the novel knob motion sensing means. The 
control device of FIGS. 16 to 18, the devices of FIGS. 19 and 20, the 
device of FIGS. 21 and 22 and the device of FIGS. 40 to 43 are examples of 
control devices which originally produce a control signal that does not 
vary in any of the standard manners in response to turning of the knob. 
As has been heretofore described in connection with the specific 
embodiments, a microprocessor or other digital signal processor 
compensates for the irregularity of the original control signal by storing 
an assigned value in association each initial value of the signal that is 
produced at successive settings of the control. The control device is 
conditioned for this by turning the knob to each of its settings and 
entering the desired assigned value for the control signal at each setting 
into a look-up table in the signal processor. Thereafter the processor 
responds to movement of the knob by converting the original signal values 
to the associated assigned values. The converted signal is then used as 
the control signal for the controlled circuit. 
This method of signal processing can be used to impart any desired response 
curve to successive settings of the control without regard to the actual 
response curve of the knob movement sensing means. 
In others of the previously described circuit control devices the response 
curve can be determined by shaping a particular component to produce the 
desired curve. For example, the output of the circuit control device of 
FIGS. 5 and 6 can be linearized by forming the resistive trace 37 to have 
a uniform degree of electrical resistance at successive locations along 
its length. The assigned signal value method can also be applied control 
devices of this kind in order to relax manufacturing tolerances and 
thereby enable more economical production of such devices. Use of assigned 
signal values compensates for manufacturing irregularities in the shape of 
resistors or other components. 
The method can also prolong the useful life of circuit control devices. If 
changes occur in the control signal at one or more settings of the control 
over a period of time due to wear or other causes, the control can be 
repositioned at those settings and a new assigned value can be entered 
into the look-up table of the signal processor for each such setting. 
The method is not limited to use with circuit controls which are disposed 
on the face of an image display device nor to controls of the type which 
have a turnable knob. It is equally applicable to controls having knobs 
which move in a different manner such as, for example, knobs which are 
slid along a linear path as in linear potentiometers or faders. 
As previously described, locating electronic components of a control device 
in front of the panel which supports the device greatly facilitates 
maintenance and repair of the control as the components can be accessed 
simply by detaching the turnable knob from the control rather than by 
opening a housing and performing operations at the back of the panel. 
FIGS. 48 to 51 depict another embodiment of the invention which is 
particularly advantageous in this respect. 
The control device 448 of FIGS. 48 to 51 again has an annular base member 
449 affixed to a transparent overlay plate 451 which is disposed against 
the face of a flat panel display 452 and a turnable knob 453 is snap 
fitted on the base member in the previously described manner. The control 
signal producing means 454 are attached to a removable carrier 456 which 
is fitted within the base member 449 and which is easily accessed by 
simply removing the detachable knob 453 from the base member. 
The carrier 456 of this example is a cup shaped member having an outside 
diameter conforming with the inside diameter of the base member 449. 
Referring to FIGS. 47 and 49 in particular, small protrusions 457 at 
opposites sides of the carrier 456 snap engage in conforming openings 458 
in the inner wall of base member 449. Each such protrusion 457 is located 
on a deflectable tab 459 portion of the carrier side wall that is formed 
by slots 461 in the side wall at each side of the protrusion. Thus the 
protrusions 457 may be disengaged from the openings 458 by finger pressure 
on the free ends 462 of the tabs 459. The free ends 462 are preferably 
right angled relative to the other portions of the tabs 459 to facilitate 
manual squeezing of the tabs. 
The control signal producing means 454 of this example is a rotary 
potentiometer of conventional internal design. The turnable shaft 463 of 
the potentiometer extends into a conforming passage in knob 453 of the 
control device 448 and a set screw 464 extends radially within the knob 
and bears against the shaft to constrain the shaft to turn with the knob. 
Alternately the shaft 463 may be engaged by a screw which extends along 
the axis of the knob 453 from the center of the face of the knob. 
The conventional potentiometer 454 of this example may be replaced with any 
of the knob motion sensing circuits that have hereinbefore been described. 
Referring to FIGS. 47, 50 and 51 in particular, electrical connection of 
the potentiometer 454 to signal and power conductors 466 that extend 
through the bases of base member 449 and overlay plate 451 and along the 
back of the overlay plate is provided for by spring contacts 467. At the 
location of each such conductor 466 one spring contact 467 is secured to 
the base of base member 449 and another is secured to the base of carrier 
456 in position to contact and bear against each other when the carrier is 
fitted into the base member. As best seen in FIG. 51, each such contact 
467 has a resilient member 468 of generally U-shaped configuration when in 
an uncompressed state with one arm of the member being disposed against 
and secured to a conductive pad 469. 
A single one of the spring contacts 467 may be used at each conductor 466 
if the other spring contact is replaced with a conductive pad. 
FIG. 52 depicts a modification of the control device in which the spring 
contacts are replaced with pin connectors 471. Pins 472 which extend from 
the base of carrier 456a enter conductive sleeves 473, which are embedded 
in the base of the base member 449, as the carrier is being inserted into 
the base member. 
The knob 453 of the embodiment of FIG. 52 does not snap engage on the base 
member 449a. Referring jointly to FIGS. 52 and 53, an outward protruding 
annular lip 474 encircles the outer wall of base member 449a. Radially 
directed passages 476 extend through the side wall of knob 453 at opposite 
sides of the knob and at locations which cause the passages to be directed 
toward lip 474 when the knob is engaged on base member 449a. A slidable 
clamp 477 is disposed in each such passage 476 and has a groove 478 which 
receives an adjacent portion of the lip 474 when the clamp is pushed into 
abutment with the knob 453. A set screw 479 within a threaded outer 
portion of each passage 476 is turnable with a screwdriver or the like to 
selectively force the clamp 477 into abutment with the knob 453 at which 
position the clamp holds the knob on base member 449a while allowing 
rotary motion of the knob. Opposite turning of set screw 479 allows the 
clamps 477 to retract from the knob 453 when the knob is to be detached 
from the base member 449a. The portion of the side wall of knob 453 which 
extends towards the image display device 452a from the location of lip 474 
has an inside diameter which is at least equal to the diameter of the lip. 
This form of engagement of the knob 453 and base member 449a may be 
substituted for the previously described snap-on engagements in instance 
where the face of the flat panel display 452a is fragile and the force 
which is applied to effect a snap-on engagement might create a risk of 
breakage. 
Except as described above, the embodiment of FIGS. 51 to 53 may be similar 
to the embodiment of FIGS. 47 to 50. 
Referring jointly to FIGS. 54 and 55, electrical connections between a 
replaceable carrier 501 for electronic components of a rotary knob type of 
circuit control 502 and conductors 503 which extend along the transparent 
cover plate 504 of the flat panel display 506 can also be made by spring 
contacts 507 situated at the side of the carrier and which function to 
snap engage the carrier in place within the base member 508. The carrier 
501 has an indentation 509 in its side which in this example is an annular 
groove that encircles the carrier. Contacts 507 have curved upper ends 
which extend into the indentation 509 to clasp the carrier 501 in place 
after it is inserted into the base member 508. The contacts 501 are formed 
of resilient conductive material and are tensioned to bear against 
conductive inserts 511 which are embedded in the outer wall of the carrier 
501 at indentation 509. Inserts 511 connect with the electronic components 
512 which are within the carrier 501 and which may be of any of the 
previously described forms. 
The resilient spring contacts 507 deflect momentarily as the carrier 501 is 
being entered into the base member 508 and then seat in indentation 509 to 
hold the carrier in place. The resiliency of the contacts 507 also enables 
withdrawal of the carrier 501 from base member 508 after the rotatable 
knob 513 has been disengaged from the base member. 
For purposes of example FIGS. 54 and 55 depict a Hall effect type of 
control of the kind previously described with reference to FIGS. 40 to 43. 
Thus a magnet 193 is secured to the rotatable knob 513 of the circuit 
control 502 at a location adjacent to the carrier 501. Other electronic 
components 512 of the previously described Hall effect knob position 
sensing circuit, such as the Hall effect sensors, are within the 
replaceable carrier 501. This circuit has four of the spring contacts 507. 
As previously described, other types of knob position sensing circuit may 
have a different number of such contacts. 
The spring contacts 501 extend between base member 508 and cover plate 504 
and contact conductive pads 520 that are connected to the conductors 503 
that extend along the plate to connect the control 502 with a controlled 
circuit in the previously described manner. 
The knob 513 of this example is snap engaged on base member 508 by a 
resilient clasp 40 in the manner previously described with reference to 
FIGS. 5 and 6. A linear key protrusion 515 on the inner surface of the 
knob 513 is entered into a conforming groove in the outer wall of base 
member 508 to assure that the spring contacts 507 are positioned to 
contact inserts 511. Any of the other previously described forms of 
engagement of the knob on the base member may also be utilized. 
Referring to FIG. 56, any of the previously described embodiments of the 
invention may be adapted to function as a switch in addition to providing 
a circuit control signal of operator selected magnitude. For purposes of 
example, the control device 481 of FIG. 54 is of the form which uses a 
magnet 193 and analog Hall effect sensors 194 to track rotary motion of 
the knob 482 as previously described with reference to FIGS. 40 to 43 and 
in which the knob is held on the base member 483 by a resilient clasp 40 
as previously described with reference to FIGS. 5 and 6. 
To provide switching signals for turning a controlled circuit on and off or 
for other purposes, the knob 482 of this embodiment has a conductive metal 
core 484 with the cylindrical side wall of the core being covered by a 
layer of electrical insulation 486. The base member 483 of the control 
device 481 and the clasp 40 which holds the knob on the base member are 
also formed of conductive metal. A conductor 488 extends from the base 
member through the transparent cover plate 489 to which it is affixed and 
along the back of the cover plate to connect the conductive core 484 of 
the knob with the input of a touch sensing circuit 487. The touch sensing 
circuit 487 may be of any of the known forms which produce a switching 
signal, for such purposes as turning lamps on and off for example, in 
response to touching of a conductor by an operator. 
The operator may selectively initiate a switching signal by touching the 
exposed surface 491 of the conductive knob core 484 at the front of the 
knob. Insulation 486 prevents unwanted production of switching signals 
when the operator grasps the sides of the knob 482 in order to turn the 
knob. 
The image display devices of the previously described circuit controls are 
of the form known as flat panel displays wherein orthogonally extending 
arrays of x busbars and y busbars enable activation of different 
combinations of image pixels at different times to create changing images. 
Some newly developed display of this kind are flexible and can have a 
curved configuration. The term panel display as used herein and in the 
appended claims should be understood to refer to displays which have a 
curved shape as well to displays having a planar configuration. 
Referring to FIG. 57, the image display device 492 which provides 
changeable graphics 493 in proximity to a turnable knob 494 of any of the 
previously described circuit control devices can be of the cathode ray 
tube type commonly used as computer monitors, in television receivers or 
for other purposes. The knob and base assembly 496 of any of the 
previously described types is affixed to the screen 497 of the cathode ray 
tube 492 or to a transparent overlay plate 498 which is superimposed on 
the screen. 
The flat panel displays of the previously described embodiments are of the 
type in which grids of busbars are used to energize particular image 
pixels in an array of pixels as needed to form a desired image. Referring 
to FIG. 58, the flat panel displays 516 can be of the known segmented 
electrode type in which electrical energization of electrodes 517 within 
the display produces images corresponding to the configuration of the 
electrodes. Such electrodes can, for example, be configured and positioned 
to provide changeable calibration marks for a rotary knob 519. As is 
understood within the art such a display can be used to image any desired 
numeral from 0 to 9 by selective energizing of electrodes 518 which are 
electrically isolated from each other and which are arranged in the form 
of a slanting squared number 8. 
While the invention has been described with reference to certain specific 
embodiments for purposes of example, many variations and modifications are 
possible and it is not intended to limit the invention except as defined 
in the following claims.