Note: Descriptions are shown in the official language in which they were submitted.
1 ~7~31 ~
This application discloses~ improvements in and
modifications o~ the inYention disclosed in my. ~.S. Patent
No. 4,052,923, issued October 11, 197.7.
My U.S. Patent No. 4,052,923 discloses a frequency
.control strip 5 formed by a potentiometer which comprises an
elongate resistive member and a sensing electrode which can
. be applied to the resistive member at a position intermediate
- its ends. As shown in Figures 2 and 2A of the patent, the
frequency control strip 5 comprises a metal strip 6 secured
by adhesive on its underside to the upper surface of a slat
3, two lengths of spacer strip 7, for example double adhesive
tape, covering the edges of the metal strip 6 but leaving the
central area exposed, a resistive strip comprising a length
of recording tape 8 having its edges secured to the spacer
strips 7 of double adhesive tape and having its magnetic
emulsion on the surface facing the metal strip 6, and a pro-
tective covering 9 of electrically non-conductive rayon ribbon.
Normally, the spacer strips 7 of double adhesive
tape keep the recording tape 8 spaced from the strip 6.
However, when pressure is applied to the covering 9, the
recording tape 8 is pressed onto the strip 6 and establishes
electrical connection therewith.
The electrical arrangement of the strip 6 and the
tape 8, which constitute the active parts of a frequency-
control voltage source, is illustrated in Figure 4 of the
,,
117~3~ 1
--2--
patent. Thus, the opposite ends of the tape ~ are connected,
through a variable range control resistor 10 and a diode
drop 33 respectively to the positive and negative poles of a
DC voltage source. The metal strip 6 effectively constitutes
a wiper contact which taps ofr from the tape 8 a voltage
dependent upon the position along the slat 3 at which
pressure is applied to the covering 9, and applies that
voltage to the VCO and/or VCF of an electronic music synthe-
sizer, as shown, or to the frequency-related circuitry of a
musical instrument.
The recording tape actually used is Scotch No. 208,
having a resistance of about 50,000 ohms/inch, and having a
width of 1/4".
The potentiometer provides the advantages of a
linear controller, including the capabilities of making swift
and subtle changes of intonation and of producing a true
vibrato (continuous fluctuating frequency).
The protective covering 9 of rayon ribbon is not
essential to the invention disclosed in the patent, ~ut if no
protective covering is provided the fingers of ~he musician
using the frequency control strip will be in continual and/or
repeated sliding contact with the back surface of the tape,
moving along its length. In such a case, the back of the
tape should be provided with an abrasion-resistant coating,
for example comprising carbon pigment suspended in a binder.
Magnetic recording tape is relatively flimsy
material, not well adapted to subjection to continual and/or
repeated pressure and sliding contact under the conditions
encountered in the frequency control strip described in the
patent (although it is recognized that it is inherent in
normal use of magnetic recording tape that it is subject to
continual pressure by sliding contact with, the components
of a tape recorder or playback machine). Therefore, the mag-
netic recording tape should preferably have a polyester base
(to resist moisture, and for good stability and mechanical
characteristics), preferably of greatest standard thickness
(about 1.5 mils), and with a magnetic oxide coating of
~ 1743~ 1
--3--
greatest standard oxide-thickness ~about 0.65 mils~. It is
also desirable that the tape and most or all of the remaining
parts of the frequency control strip should be made an easily
replaceable subunit like a string of a guitar or violin.
Under such an arrangement, all or part of the frequency con-
trol strip, including its three terminals and perhaps even
all or part of the underlying support (the slat 3 of the
patent) should be easily removed and replaced, the terminals
being provided with plugs or clamps and the rest of the fre-
quency control strip, and possibly also at least part of thesupport, being removable and replaceable by way of plugs,
clamps or adhesive.
In order to provide an electronic musical instrument
playable as a violin, viola, cello or double bass, four
movable slats as described in the patent, each provided with
its own frequency control strip, are arranged in parallel, on
a base the size and shape of the standard ~acoustic instrument)
fingerboard. The player's left hand fingers the slats as if
they were strings, and since the fingering action here also
controls triggering and the loudness level, the player's
right hand is free for other operations, such as manipulating
waveform-variation controls and/or VCA controls, filters etc.
In order to provide an electronic substitute for
the strings of a guitar, electric bass or other fretted
instrument, four to six slats, each provided with its own
frequency control strip, are arranged in parallel on a base
the size and shape of the standard (acoustic instrument)
fretboard. Again, the player's left hand fingers the slats
as if they were strings, and since the fingering action also
controls triggering and loudness level the player's right
hand is free for other operations. The function of frets can
be retained by providing indicia in the standard fret
positions on the protective covering or other uppermost sur-
face of each movable slat. The indicia may be either purely
vi~ual, such as colored or etched lines on the protective
covering, or partly tactile, alternating, on the uppermost
surface, both relatively wide smooth regions with narrower
~ ~7ll31 1
--4--
fret-like rough regions fo~med by scoring or grooving, for
example, distributed along its length.
In order to provide an electronic instrument play-
able by a keyboard player, the slat would be about 2 inches
wide and the protective covering would be formed with a
black and wh~te keyboard pattern. The black keys and the
divisions between the white keys could be provided with a
different tactile effect from the white keys themselves,
as by rough surfaces, Such an instrument would have only
1~ monophonic capability. In order to provide 2-voice polyphonic
capability, two such slats are placed end to end and each
played by a different hand. In order to provide 4-voice
polyphonic capabiltiy, an additional pair of slats, end to
end, are placed slightly behind and slightly higher than the
~irst pair, so that the entire assemblage looks like a 2-
manual organ keyboard.
One problem with use of the frequency control strip
described in the patent is that in a keyboard instrument the
control strip is controlled by application of pressure within
a narrow zone defined by the portion of the width of the -
resistive strip 8 which upon pressure establishes electrical
contact with the metal strip 9, whereas the player of an
instrument having a keyboard of standard piano-forte or
professional-model organ dimensions is accustomed to applying
finger-pressure within a much deeper zone, the maximum depth
of which is the length of a long (white) piano key (5.75
inches), although the fingers are usually applied within a
somewhat shallower zone (about 3 inches) which extends from
the front edges of the long keys to slightly behind the front
edges of the short (black) keys. In order to overcome this
problem a resilient comb-like member is secured to the slat
with the teeth extending perpendicular to the length of the
slat and terminating superjacent the recording tape. If the
comb is made of conductive material, it may be used in place
of the metal strip 6 of the potentiometer of the patent, by
omitting any protective covering over the recording tape and
positioning the recording tape with its magnetic surface up-
~ 17431 ~
ward facing the ~erminations of the teeth~ A protectivecovering could then be provided over the comb~ the protective
covering having a printed black and white keyboard pattern.
Alternatively, the metal strip could be retained, and the
comb arranged so that when the teeth engage the recording
tape the tape is pressed down into contact with the metal
strip, just as it is pressed down by finger pressure into
contact with the metal strip in the case of the control strip
described in the patent. By use of a comb of suitable width,
the musician ma~ be provided with a finger-contact zone of
standard depth (about 3 inches), since he can apply pressure
at any point along the teeth, and the teeth transmit the
pressure to the much shallower zone of the record.ing tape.
In order to retain the desirable glissando control, the
teeth should be as fine as possible so as to simulate an
unbroken contact surface. If glissando control is regarded
as relatively unimportant, the comb may be constructed to
provide only one tooth for each key, and the teeth themselves
may be black or white, as required for a conventional key-
board, and the black teeth could be positioned higher thanthe white teeth, in order to provide a three-dimensional key-
board surface.
According to the present invention there is pro-
vided a potentiometer, comprising a support member having
first and second support regions and an intermediate region
located therebetween, and a resistive member supported on
the support member at said first support region and having
a longitudinal dimension extending transversely of a line
from the first support region to the second support region,
characterized in that a resilient contact member is secured
to the support member at said second support region in con-
cantilever fashion and extends over the intermediate region
and terminates superjaoent the resistive member, the contact
member being flexible both about axes which extend parallel
to said line and about axes which extend transversely of
said line, whereby application of pressure to the contact
member at a location over said intermediate region causes
1 17431 1
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the contact member to bend resiliently about an axis per-
pendicular to said ~ine and to engage the resisti~e member
and movement of the point of application of pressure per-
pendicular to said line causes the point of engagement of
the resistive member by the contact member to move along
the longitudinal dimension of the resistive member.
According to a second aspect of the present inven-
tion there is provided a potentiometer, comprising a support
member having first and second support regions and an inter-
mediate region located therebetween, and resistance meanssupported on the support member at said first support regions
and comprising a resistive member and a sensing electrode
which are spaced apart from each other but, on application
of pressure, come into contact with each other, and having
a longitudinal dimension extending transversely of a line
from the first support region to the second support region,
characterized in that a resilient contact member is secured
to the support member at said second support region and ex-
tends over the intermediate region and terminates superjacent
the resistance means, the contact member being flexible both
about axes which extend parallel to said line and about axes
which Pxtend transversely of said line, whereby application
of pressure to the contact member at a location over said
intermediate region causes the contact member to bend
resiliently about an axis perpendicular to said line and to
engage the resistance means, and movement of the point of
application of pressure perpendicular to said line causes the
point of engagement of the resistance means by the contact
member to move along the longitudinal dimension of the re-
sistance means, so that when the ends of said resistive mem-
ber are connected to opposite respective poles of a voltage
source a voltage may be tapped off from the resistive member
by way of said sensing electrode by appl~ing pressure to the
intermediate region of the contact member, the tapped-off
voltage being selectively variable by varying the position
along the contact member at which pressure is applied thereto.
Certain of the improvements and modifications
~ 1 7 ~
discussed above will now be described in fur~her de~ail
with reference to the accompanying drawings in which:-
Figure 1 shows a cross-sectional view of a device
for generating a Relected voltage;
Figure 2 shows a detail of the device illustrated
in Figure l;
Figure 3 shows a plan view of one component of
the Figure 1 device
Figure 4 shows a plan view of the device illustrated
10 in Figure l;
Figure 5 ~hows a longitudinal sectional view of a
first modification of the device illustrated in Figure 1,
while Figure 5A is a circuit diagram showing the electrical
circuit used with the Figure 5 device;
Figure 6 shows a vertical sectional view
illustrating additional components of the Figures 1 and 5
devices, while Figure 6A is an elevational view taken in
the direction of the arrow VIA of Figure 6 and Figure 6B
shows the ele~trical arrangement of these additional
20 components,
Figure 7 shows an end view of a second modification
of the devios shown in Figure 1, while Figure 7A shows a
front elevation of the device, Figure 7B shows a longitudinal
sectional view, to an enlarged scale, of part of the device;
25 and Figure 7C shows a circuit diagram of this modification;
Figure 8 ~hows a longitudinal sectional view of
a first modification of the Figure 7 device, while Figure 8A
is a circuit diagxam of this modification;
F~gure 9 shows a fragmentary plan view of a second
30 modification of the Figure 7 device, while Figure 9A shows
a circuit diagram of this modification and, Figure 9B shows
a circuit diagram of a modification of the Figure 9 de~ice;
Figure 10 shows a circuit diagram of a further
modification of the Figure 7 or 9 device;
Figure 11 shows a cross sectional view of one
component of one v~rsion of the device employing the
Figure 10 circuit; and
~1743~ ~
--8--
Figure 12 shows a circuit diagram of a further
modification of the device illustrated in Figures ~ and 9A.
The device illustrated in Figure 1 comprises a slat 3 which
is mounted upon a support (not shown) in the same manner
5 as the slat 3 of the patent. A frequency control strip 5
extends along one edge of the slat 3. As illustrated ~n
Figure 2, the frequency control strip comprises a metal
strip 6 secured by adhesive on its underside to the upper
surface of the slat 3, two lengths of spacer strip 7, for
10 example double adhesive tape, covering the edges of the
metal strip 6 but leaving the central area exposed, a
resietive strip comprising a length of recording kape 8
having its edges secured to the spacer strips 7 of double
adhesive tape and having its magnetic emulsion on i~s
15 under surface (facing the metal strip 6), and a protective
CQVering 9 of electrically non-conductive rayon ribbon.
Normally the spacer strips 7 of double adhesive
tape keep the recording tape 8 spaced from the strip 6.
Howe~er, when pressure is applied to the coverlng 9, the
20 recording tape 8 is pressed onto the strip 6 and establishes
electrical connection therewith. The electrical arrangement
of the strip 6 and the tape 8 æe as described in the patent.
A resiliént member 34 is mounted on the slat 3
with one edge secured to the slat, along the opposite edge
25 from the frequency control strip 5, by means of screws 35.
An intermediate part 34' of the member 34 extends acro~
the slat 3, perpendicular to its length~ and slightly spaced
ab~ve its upper surface. The free edge of the member 34 is
bent at 34a downward and/or into a U-shape. It wiil be
30 appreciated that since the member 34 is secured to the slat
along only one edge, the other edge being spaced from the
slat, the member 34 is supported in cantilever fashion.
As in the case of the frequency control strip
described in the patent, the recording tape is Scotch No.
35 208 having a resistance of about 50,000 ohms/inch. The
width of the tape is one quarter inch. The depth of the
part 34' of the member 34 is about 3 inches. The member
~17~3~ ~
_g _
34 is flexible both about longitudinal axes extending
parallel to its edges and about axes extending transverseIy
of its edges. When pressure is applied to the intermediate
part 34' of the member 34, the corresponding lowermost
5 point of the edge 34a moves down into engagement with the
protective covering 9 and thus presses the recording tape
8 into electrical connection with the metal strip 6. Thus,
the member 34 serves as a transmission device for concen-
trating the effect of pressure applied at any point over a
10 reIatively deep area (the depth of the part 34') into a
relatively shallow area (the width of the recording tape).
Of course, the member 34 should not be so flexible about
longitudinal axes that application of pressure to the
member causes the entire edge 34a to move down into engage-
15 ment with the protective covering 9. As illustrated inFigure 3, the member 34 may be in the form of a comb having
its back secured to the slat 3 by the screws 35 and the
individual teeth 3Ç of the comb being so narrow and closely
spaced that use of a single fingertip to apply pressure to
20 the comb will press the tips 36a of several adjacent teeth
simultaneously against the protective covrsring 9.
The upper surface of the member 34 may be covered
by a flexible protective covering 37 (which is preferably
eIectrically inert), for example a plastic film, having
25 on its upper surface a smooth and rough and~or black and
white pattern 38, as shown in Figure 4, similar to the
pattern of black and white ke~s of a piano keyboard, and
with:lines 39, printed on or scored into its surface and
extending perpendicular to the length of the slat near the
30 middle of the key position, as a guide to the player showing
the location of the underlying tooth which, on contacting
the covering 9, produces a note of the exact or "correct"
pitch for that key, for observance of the standards of
fixed-intonation tuning.
In a modification of the device illustrated in
Figures 1 and 2, the frequency control strip 5 comprises only
a strip of recording tape which has its back surface secured
~t~d~3~1
--10--
to the slat, so that its magnetlc coating is faclng upwards,
and the moving part of the fre~u~ncy control 5trip comprls~s
the member 34. In this casel the member 34 is made of
conductive material and is connected in the same manner as
S the metal strip 6 of the frequency control strip 5 of the
patent. Of course, in the case of th1s modi~icatlon the
protective covering 9 is not retained, but in order to
prevent leakage currents and other perturbations when the
musician presses the member 34 a protective covering is
10 required and this must be made of electrically non-conductive
material, such as plastic film. The covering may bear
the same type of pattern and/or lines as the protective
covering 37 of the device illustrated in Figures 1, 2 and
3. As in the case of Figure 1, the member 34 may have a
15 continuous intermediate portion 34', provided that it is
sufficiently resistant to bending about the axes extending
longitudinally of the slat, or the member 34 may be in
the form of a comb ~ith teeth 360
It is preferred that the member 34 be in the
20 form of a comb with teeth 36, rather than have a contlnuous
intermediate part 34', because although sultable materials
are available to produce the member 34 with a contlnuous
intermadiate part 34' ~i.e~ materials are avallable with
suitable resilient and flexible qualities~, the physi~al
25 properties of the member 34 depend upon the conditions
under which the member was produced, and the condi~ions
under which the material of the member 34 was produced,
and change with time, and therefore the difference in
flexible and resilient qualitles about the different a*es
30 cannot be relied upon to obtain in the future, whereas in
the case of a comb it is only necessary that each tooth
remain flexible about axe~ extending longitudlnally of the
slat: flexibility of the member 34 about axes perpendicular
to the slat is achieved by vlrtue of the member being
35 in the form of a comb, not upon the physical properties of
the material from which the member is made, and 90 will
not be affected by passage of time.
1 ~7431 1
In a fur~her modlfication o~ the device illustrated
in Figure 1, the L`Le~UenCy control strip 5 i8 rep~aced by
a series of discrete electrical contacts S' illustrated in
Figure 5 which are connected to respectlve points of
5 different potential in a chain of resistors 8i, illustrated
in Figure 5A, which takes the place of ~he recording tape 8
In the case of the Plgure S embodiment, the intermediate
portion of the member 34 ma~ be continuous as in the case
of the other described embodlments, but it is preferable
10 that the member 34 should, as illustrated~ be a comb
having one tooth 36 for each of the discrete con~acts 5'0
It will be appreciated that each of the contacts 5'
establishes a discrete voltage level which, when applied to
a VC0, VCF or other unit whose pitch or fre~uency response
15 is affected by voltage, establishes a predetermined
frequencyO Thus, the de~ice illustrated in Figure 5 i~
monophonic, and iæ especially well suited for playlng
fixed-intonation music,
As in the case of the device disclosed in the
20 patent, in each of the devi~es il1ustrated in Figur~s 1 to
5 the siat 3 and the base member 1 upon whicn it is
supported are provided with parts for g~eratlng an
electrical analog signal dependent on the po~ition of Ihe
slat with respec~ to the base member, and rhe de~ice i5
25 al50 provided with means for genera~ing a prede~ermined
response when the slat is moved from a null position through
an initiating thresholc posikion against the bias establlshed
by a tension spring and for terminating the re~ponse when
the support meml,er is returned from beyond ths initiatlng
30 threshold positlon towards the null positlon through a
termination threshold positlon. These additional components
are illustrated in Figures 6, 6A and 6B and comprise light-
emitting diodes 11 and 12, a light dependent re~istor 13,
a photodiode 14 and a trigger circuit lS~ The light
35 dependent resistor 13 is one component of a T-network 13a,
which comprises in addition two resistors 13D and two
capacitors 13c.
~ -~7431 1
-12-
It ls a1so posslbi.e to use the princlple~ of the
devices illustrated in Figures 1 to 5 to produce a pol~phonlc
device. In such a dev~ce, a plurality of relatively short
slats 3' forming keys are mounted side by side on a base
5 member l as shown in Flgures 7, 7A and 7B by mean~ of
respective hinges 20 Each of the keys 3l is provided with
its own frequency control strip Sl and pressure transmitting
member 34 having a solldl~ colored protective covering 37.
above it di~playing an în tune or exact pitch indicator line.
lO Each frequency control strip 51 and pressure transmitting
member 34 may be constructed as described with reference
to Figures l and 2 or as described with reference to the
modification in which the frequency control strip comprises
only a strip of recording tape~ The output from each of
15 the metal strips 6 ~in the case of the Figure l construction)
or from each of the members 35 ~in the case of the modifica-
tion) is processed in the same manner as the output from
the metal ~trip 6 of the patent, up to but not including
the power amplifler 30 and loudspeaker 26 shown in Flgure
20 5 and 6 of the patent~ In thls polyphonic devlce, a1l the
outputs from the VOC~VCF circultry 20~21 fea by metal
str~ps 6 or members 34 are indlvidually attenuated by
light-d~pendent re iStoLs 13 assoclated with the respective
keys 3' and are then mixed together in a mixer 30a and fed
25 into a single power amplifler 30 driving a sing`le loud-
speaker 26, as illustrated in ~lgure 7C,
The device illustrated in Figures 7, 7A, and 7B
may be modified in the light of the teaching of Figure~ 5
to 5A to provide a monphonic instrument, as illustrated in
30 Figure 8, in which each of the frequency control strips 51
is replaced by a di~crete electrode 51' and ~he separate
electrodes are connected a~ illustrated in F~gure 5A. The
member 34 connected to each key 3'has a continuous intermedl-
ate portion 34' and is not in the form of a comb. However,
35 in the case of Figures 7, 7A and 7B each indi~idual key 3'
has its own set of components for triggering and amplitude
control. The different pressure transmi~ting members 34, of
~ 1743 1 1
-13-
the keys 3' respec~iveLy, are conn2cled together to a common
output which i~ ultimately connected to a VC0, VCF or other
unit whose pitch or fxequency response is affected by
voltage as shown in Figure 5A . Of course~ the respective
5 protective coverings provided on the keys 3' respectiveIy
are solidly colored and since discrete contacts are used
the coverings are not provided with in tune or exact pitch
indicators as in the case of Figure 7~
The device of Fiyure 8 may also be modified to
10 provide a polyphonic devlce in which each key has a fixed
intonation, rather than a variable intonation as in the
case of the polyphonic device of Figures 7, 7A and 7B.
In the case of this modification the electrodes 51' are
connected to respective po~ential dividers, establishing
15 discrete voltage levels for the electrodes, as shown in
Figure 8A~ Each potential divider comprises a fixed
resistor 45 and a variable trlmmer resistor 46 connected in
series with a diode drop 33 between the positive and
negative poles of a D,C~ voltage source. The different
20 pressure transmit~lng members 34 are connected to respecti~e
VCO's and VC~'s as in the case of Figure 7C, and each ke~
is provided with its own set of componen~s for triggering
and amplitud control.
In a development shown in Figure 9 of the device
25 illustrated in Figures 7, 7~ and 7B a single elongate
member 40 of resilient material is secured on one of its
two longer edges by screws to a base member 1 and is formed
with cuts 42 extending perpendicular to its other long edge
and dividing that part of the member 40 which pro~ects
30 from the base member 1 into a series of long and short keys
43 and 44 respectively ~n such a way that the entire
member 40, viewed from above~ reqembles a piano keyboard,
with the length and width of each of the keys 43 and 44
equal to those of ~he corresponding piano keys. Each of
35 the keys 43 and 44 has itS own frequency control ~trip
51 attached to its upper surface adjacent the free end of
the key, and its own pressure transmis~lon member 34
~ ~4~ 1 ~
-14-
covered by a so1idly-colored protectl~e COVeElng 37 display-
ing an in tune o~ exact pltch indlcator llne 39O Each of
the keys 43 and 44 carries near its free end a light-emltting
diode 12 ~shown in Figure 9A9 which illuminates a photodiode
5 14. Each frequency control strip 51 and pressure transmitting
mem~er 34 may be constructed as described with reference
to Figures l and 2 or as described with reference to the
modification in which the frequency control strip comprises
only a strip of recording tape The output from each of
10 the metal strips 6 (in the case of the Figure l construction)
or from each of the members 34 (in the case of the modifi-
cation) is processed in the same manner as the output from
the metal strip 6 of the patent, up to but not including
the power amplifier 30 and loudspeaker 26 shown in Figure
15 6 of the par:ent. In this polyphonic device, all the out-
puts from the VCO/VCF circuitry 20/21 fed ~ metal strips
6 or members 34 are individually attenuated by light-
dependent resistors 13 associated with the respective
keys 3' and are then mixed together in a mixer 30a and
20 fed into a single power amplifier 30 driving a single
loud-speaker 26, as illustrated in Figure 9A~
The circuit illustrated in F~gure 9A corresponds
to that illustrated in Figure 6 of the patent, but a circult
corresponding to that illustrated in Figure 5 could be used instead
25 if, for example, each key carried a shutter whlch passea, on
depression of the key, between two LED's ~corresponding to
the LED's ll and 12 of the patent9 and an LDR and a photodiode
tcorresponding to the LDR 13 and the photodiode 14 of the
patent) so as to decrease the illuminatlon of the LDR and
3~ the photodiode when increaYing pressure is applied to the key.
In the case of the devlce de~cribed with referellce
to Figures 9 and 9A, each key 43 and 44 has its top surface
coplanar with the top surfaces of the other teeth, when not
subject to dewnward pressure~ However, the entire one-piece
35 member 40 may be molded or stamped in such a manner that
the top surfaces of the shorter keys 44 would, when not
sub~ect to downward pressure, be coplanar with each other in
~17431 1
-15-
a plane higher ~han that of the top surfaces of the longer
keys 43, thus givîng the entire member 40 the three
dimensional pattern shown by the arrangement of black and
white keys in a piano keyboardc
The device illustrated in Figures 9 and 9A could
be modified to produce a monophonic keyboard by providing
each of the teeth 43 and 44 with a single electrical contact
instead of a frequency control strip, connected as in the
case of the contacts 5' of~ Figures 5 and 5A. As in the
10 monophonic modification of Figures 7, 7A and 7B, the member
34 of the monophonic modification of Figures 9 and 9A would
have a continuous intermediate portion and would not be in
the form of a comb.
The monophonic modification of Figures 9 and 9A
15 could be further modified to provide a polyphonic device
having a fixed intonation for each key, rather than a variable
intonation, in the manner described with reference to
Figure 8A, i.e~ by using a plurality of potential dividers
connected to the electrical contacts respec~ively and
20 providing each key with its ~wn set of components or
triggering and ampli~ude control. In a simplified form of
these polyphonic devices the contacts 34 and the discrete
contacts associated therewith are repiaced by direct
connections between the potential dividers and the respective
25 voltage-responsive variable frequency devices 20~21, as
shown in Figure 9B.
The polyphonic devices described above allow for
variable intonation from each key. A polyphonic device may
be produced to provide the user with a choice between
30 variable intonation from each key and a fixed intonation
from each key. In order to achieve this mod1flcation, each
key is provided with a double pole, double throw switch 52,
and in one po~ition of the switch the output is taken from
the metal strip 6 or the member 34 (depending upon whether
35 the arrangement of the frequency control strip and the
member 34 is as described with reference to Figure 1 or the
modification thereof) whereas in the other position of the
~7433 1
-16-
switch the output is taken from a potential divider
establishing a fixed voltage output. A suitable switching
arrangement is illustrated in Figure 10 of the drawings.
As illustrated in Figure 10, the positive termi~al of a
5 D.C. voltage source is connected bo the negative pole thereof
through a diode drop 33 and either a variable trimmer re-
sistor 10 and the strip of tape 8 or through a fixed
resistor 45 and a variable trimmer re~istor 46, depending
upon the position of the switch 52, and the output i8 re-
10 ceived either from the metal strip 6 or member 34 or fromthe junction point of the resi~tors 45 and 46, depending
upon the position of the switch 52. The connection to the~
~unction point 47 may either be a permanent connection, as
illustrated in broken line, or it may be a second movable
15 contact 48 which is placed so that it establishes electrical
connection with anearby fixed metal contact 49, which is
connected to the junction 47, when finger pressure i8 applie~
to the protective covering 37 on the key. In the case where
the connection is made permanently to the ~unction p~int 47,
2~ and the fixed metal contact 49 and the associated movable
contact 48 are omitted, the frequency control strip can be
constructed in either of the two configurations described
above. When the contacts 48 and 49 are employed, the
fre~uency control strip is constructed in the configuration
25 illustrated in Figure 11. This mGdified form of frequency
control ~trip comprises a metal strip, forming the contact
49, secured by adhesive on its under surface to the up~er
~urface of the key 3', 43 or 44, a strip of flexible metal
tape, such as aluminum foil sensing tape, forming the contact
30 48 and secured at it~ under surface to the contact 49 by
two strips of double adhesive tape 50 covering the edges of
the contact 49 but leaving the central area exposed, a~d
a strip of recording tape, forming the tape 8, having its
under surface secured by adhesive to the upper surface of
35 the contact 48 and having its resistive coating on its
upper surface, facing towards the pressure transmitting
member 34. The pressure transmitting member 34 is covered
~17~3~ 1
~ 17-
by the protective oovermg 37- Normal~y the spacer strips 50
of double adhesive tape keep the contact 48 spaced from the
contact 49, but when pressure s applied to the protective
covering 37, the member 34 engages the tape 8 and the contact
5 48 is pressed onto contact with the contact 49 and establinhes
electrical connection therewith.
An additional and optional feature for a polyphonic
keyboard configuration would be to have a single "glissando
strip" placed in the very fron of the keyboard and extending
lO the full length of the latter. This "gli~sando strip"
would be one complete monophonic form of the basic unit
described in the patent, including a single movable slat,
tension spring, motion-sensing devices, frequency-control
strip, circuitry for ~onverting an analog signal into a
15 digital signal, attenuating circuitry, etc., and optionally
including a transmi~sion-comb and a protective covering
over the latter.
The monophonic modifications of Figures 9 and 9A
could be further modified to provlde a polyphonic device
20 having a ixed intQnation for each key but not deriving the
pertinent frequencies from a plurality of potential dividers
but instead deriving th~m from connections to the output~
of electronic-organ oscillator circuitry ~a one-octave se~
of oscillators 20a, each followed by a set of frequency
25 dividers 20a'], said connections feeding first through the
gating circuitry 16, 17 of my triggering circuit 15 and
then through the LDR 13 in my attenuation circuit 11, 13.
See Figure 12.
It is to be understood that the invention is not
30 limited to the specific constructions shown and descri~ed,
as it will be apparent to those skilled in the art that
changes may be made without departing from the principles
of the invention as defined in the appended claims.
