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BACKGROUND OF THE INVENTION
This invention relates in general to certain new and useful improvements in
stimulators for application of electrical stimuli pulses to an animal
body, and, more particularly, to electrically operable stimulators
including a unique pulse generator and output amplifier.
There are several forms of electrical stimulators which haave been proposed
for the relief of pain and similar purposes including body ailment healing
and accordance of certain deleterious conditions which might otherwise
arise. While the underlying pathogenesis which gives rise to these results
is generally not understood fully, the clinical manifestation is certain
and definite. For example, it has been found that application of
electrical stimuli in proximity to an incision in thoracic surgery has
been found to reduce the possibility of collapsed lungs.
Generally, it has been found that when using electrical stimulation from
these electrical stimulators, with terminals applied to the body, that the
output current introduced to the body has a substantial effect in reducing
pain sensation and producing the other effects mentioned above. With
respect to pain reduction, the exact phenomena in the reduction of pain
also is not fully understood, although it has been determined that
substantial pain reduction can be obtained through the application of such
electrical pulses.
Those commercially available stimulators presently used include, in large
measure, the now out-dated tube-type stimulators, primarily found in many
physical therapy operations. There has been a recent introduction into the
market place of these electrically operable stimulators constructed with
solid-state circuitry. However, these stimulators suffer from a number of
serious drawbacks in that they are difficult to use in that the controls
of these mechanisms cause the various components of the circuit to
interact in a rather complex way.
It is desirable to control the pulse width and the frequency and amplitude
of signal outputs from these stimulators rather carefully, in order to
achieve an optimum desired effect and to eliminate any unpleasant
sensations for the patient. However, the prior art devices were not
relatively effective in this regard since they were difficult to control,
and consequently they have not been widely accepted.
The present invention obviates these and other problems in the provision of
an electrical stimulator which includes a uniquely designed pulse
generator and a uniquely designed output amplifier which permits precise
control and generation of a desired output signal. The stimulator of the
present invention also provides a greater range of applicability due to
its ability to obtain close control and very reliable repeatability.
OBJECTS OF THE INVENTION
It is therefore the primary object of the present invention to provide an
electrically operable stimulator and method for pain reduction which is
capable of being easily and efficiently controlled for optimum desired
electrical output signals.
It is another object of the present invention to provide an electrically
operable stimulator of the type stated which can be manufactured to
operate with a relatively small number of components and which can be
constructed at a relatively low unit cost.
It is a further object of the present invention to provide an electrically
operable stimulator of the type stated which is relatively simple in its
operation and where relatively unskilled personnel can be easily trained
in its operation.
It is yet another salient object of the present invention to provide an
electrically operable stimulator of the type stated which is rugged in its
construction and highly efficient in its operation.
With the above and other objects in view, my invention resides in the novel
features of form, construction, arrangement and combination of parts
presently described and pointed out in the claims.
SUMMARY OF THE INVENTION
The present invention relates to an electrically operable stimulator for
the generation and application of electrical stimuli pulses to the body of
an animal in order to create various desired physiological benefits
including potential pain reduction. In general terms, the stimulator
comprises a pulse generator comprised of a transistor based pulse
generator which has been uniquely designed to provide a desired pulse form
without suffering any current penalty. A pulse rate control means is
operatively included in the generator for controlling the pulse rate of
the output signal. A pulse width control means is also included to control
pulse width. An amplifier output stage is also operatively connected to
the pulse generator to produce pulses of the desired intensity.
Furthermore, the amplifier output stage comprises a transformer means
which is operatively connected to provide an output signal for application
to the body of an animal.
In one aspect of the present invention, an off-on indicator light may form
part of the pulse generator to provide indication of operation of the
pulse generator. In addition, an indicator light may be provided and
connected across the transformer means in order to provide indication of
the storage level of the DC battery pack. In the same connection, a
rechargeable source of stored electrical energy may form part of the
stimulator and is operatively connected to the pulse generator.
The present invention also provides a method of providing electrical
stimuli signals for application to an animal body in order to provide
various physiological benefits including control of pain. This method will
generally relate to the generating of a continuous series of electrical
pulses. The method also includes the controlling of the pulse rate of
these electrical pulses. In addition, the method includes a controlling of
the pulse width of these electrical pulses independently of the pulse
rate. Moreover, the amplitude of these pulses is controlled independently
of the pulse rate and the pulse width to generate the desired output
signal.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus described my invention in general terms, reference will now be
made to the accompanying drawings in which:
FIG. 1 is a schematic view of an electric circuit forming part of the
stimulator of the present invention; and
FIG. 2 is a front-elevational view of a control panel forming part of the
stimulator of the present invention.
DETAILED DESCRIPTION
Referring now in more detail and by reference characters to the drawings
which illustrate a preferred embodiment of the present invention, A
designates an electrically operable stimulator which produces
physiologically beneficial results including, for example, the potential
elimination of various undesirable results arising after surgery and for
pain reduction. The stimulator A may be used as a percutaneous stimulator
or as a transcutaneous stimulator, although the invention is highly
effective as a transcutaneous stimulator.
The stimulator A comprises an internal power supply 10, a pulse generator
12, and an output amplifier section 14, as illustrated in FIG. 1, and each
of which is more fully described in detail hereinafter. These components
would be suitably mounted in a conventional housing (not shown) and which
would be provided with a control panel C, more fully illustrated in FIG. 2
of the drawings.
In general, the electrically operable stimulator is used in conjunction
with a pair of electrodes which are suitably connected to a desired
location of the body for introducing electrical signals thereto, and these
signals are generally in the form of a train of electrical pulses. The
terminals will be connected to a pair of outputs on the output amplifier
section 14, as more fully described hereinafter. These terminals are
essentially conventional in construction, and are therefore neither
illustrated nor described in any further detail herein.
With respect to the present invention, the electrically operable stimulator
has been described as being used for the effective muscle and/or nerve
stimulation through application of electrical signals to the body of an
animal. Generally, the animal will adopt the form of a human being,
although it should be understood that the invention could be operable with
any form of animal type having a central nervous system. Moreover, the
electrical signals are analog signals which generally exist in the form of
a series of pulses as indicated.
The internal power supply 10 generally comprises a rechargeable battery
pack, as for example a conventional DC battery source, designated as 16. A
recharging circuit 18 is connected across the terminals of the battery 16
and includes a load resistor 20 and a diode 22 connected in parallel to
one input terminal 24. In like manner, the other input terminal 26 is
provided with a rectifying diode 28. By definition, these input terminals
24 and 26 could be suitably connected to an external power supply (not
shown) in order to provide a source of power for recharging the battery
pack 16. In this respect, the battery operation and the recharging circuit
are not absolutely essential to the present invention, except to allow
greater ruggedness of construction.
The positive and negative output terminals of the battery 16 are connected
to conductors 30 and 32 in the manner as illustrated in FIG. 1 of the
drawings. In this case, it can be seen that the pulse generator 12 and the
output amplifier 14 are connected across these conductors 30 and 32. The
pulse generator 12 generally is constructed on the basis of a unijunction
transistor multivibrator which has been modified substantially, at least
through the provision of a high source impedance current matching
amplifier and a current limiting switching transistor, in order to achieve
a low current drain and low output impedance, for the pulse generator 12
at its output node 65 referred to negative conductor 32.
The pulse generator 12 comprises a pulse trigger 34 in the form of a
unijunction transistor and which has the base-2 terminal thereof connected
to the negative conductor 32 and the base-1 terminal thereof connected to
the positive conductor 30 through a compensating resistor 36. The resistor
36 is designed to provide temperature compensation and also serves as a
current limiting resistor for the unijunction transistor. The emitter of
the unijunction transistor 34 is connected through a resistor 38 to a
potentiometer 40 or other form of condensor charging control device, for
control of current. In this respect, and by reference to FIG. 2, it can be
observed that the potentiometer 40 is provided with a control knob 42
mounted on the front control panel C forming part of the stimulator of the
present invention.
It should be understood that the term unijunction transistor as used herein
will include the programmable unijunction transistor, and in which case
the gate electrode (corresponding to the emitter electrode of the
transistor 34) would be connected to the resistor 38. Moreover, the
resistor 38 is merely auxiliary to the resistive potentiometer 40 and
forms part of a resistive ladder therewith.
A capacitor 46 is also connected to the emitter of the unijunction
transistor 34 and to an NPN transistor 48 which serves as a pulse forming
transistor. The emitter of the transistor 48 is connected to the negative
conductor 32 and the collector of the transistor 48 is connected through a
resistor 50 to the positive conductor 30, in the manner as illustrated in
FIG. 1.
The pulse generator 12 is also provided with a high current gain, high
impedance amplifier 52 in the form of a pair of base-emitter connected NPN
transistors, or so-called Darlington configuration, as shown in FIG. 1 of
the drawings. It can be observed that the amplifier 52 has the base of one
of its transistors connected to the collector of the pulse forming
transistor 48 and the common collector terminal of the amplifier 52
connected to the positive conductor 30. The amplifier 52 effectively
serves as an impedance changing amplifier and is designed to provide a low
impedance output in a manner hereinafter described.
The pulse generator 12 also includes a current limiting resistor 58 and a
shorting switch 54 (preferably composed of two transistors in the
Darlington configuration) as connected in FIG. 1 of the drawings. In this
case, one of the transistors in the switch 54 has a base which is driven
by the emitter output of one of the transistors in the amplifier 52
through a coupling resistor 55. The switch 54 is connected to the base of
the transistor 48 and the resistor 55 also is connected to the output of
the amplifier 52 at output node 65.
The collector terminal of the Darlington configured transistors in the
shorting switch 54 is connected through a resistor 56 to a pulse width
control potentiometer 60, the latter also having one terminal connected to
the positive conductor 30. The potentiometer 60 is operable by means of a
pulse width control dial 62 mounted on the control panel C, as illustrated
in FIG. 2 of the drawings. Again, the resistor 56 is auxiliary to the
potentiometer 60 and forms part of a resistive ladder therewith.
The collector terminal of the shorting switch 54 is also connected to the
current limiting resistor 58 which is, in turn, connected to the capacitor
46, the emitter terminal of shorting switch 54 and the base of the pulse
forming transistor 48 at a junction 59, in the manner as illustrated in
FIG. 1.
The output of the amplifier 52 is connected through a resistor 63 and a
light emitting diode 64, the other terminal of which is connected to the
negative conductor 32. The light emitting diode 64 is also mounted on the
control panel C and is included to provide an indication of a "power-on"
condition, when energized through the circuit of the present invention. It
can be observed that the use of the resistor 63-diode 64 circuit is only
optional and not necessary in the present invention.
By further reference to FIG. 1, it can be seen that the emitter output
terminal of the amplifier 52 is connected to a common junction with the
resistor 55 and the resistor 63 to form an output node 65. Thus, the
amplifier 14 is effectively connected to this output node 65, as well as
the positive and negative conductors 30 and 31, respectively.
In essence, the unijunction transistor 34, the pulse forming transistor 48
and the capacitor 46, along with the resistors 36 and 50, the combination
resistance ladder comprised of resistors 38 and 40 and combination
resistance ladder comprised of resistors 56 and 60, form a pulse
generator. The resistor 36 serves as a compensating resistor in this pulse
generator.
The high source impedance amplifier 52 permits a high value of load
resistor 50 to be used in conjunction with the pulse-forming transistor
48, to reduce the collector current of transistor 48. This improves
circuit efficiency, since the transistor 48 is active when the pulse
generator 12 is in the "off" state only.
It can be observed that the switch 54 and the resistor 58, in combination,
provide a unique current controlling switching means with respect to the
circuit of the present invention in permitting generation of narrow
pulses. Without the presence of these two components, if the potentiometer
60 were set to a low value, then a high current would flow through the
base-emitter through the circuit of pulse-forming transistor 48 during the
"off" state of the pulse generator, which would accomplish no useful work
whatsoever. It can also be observed that a high current flow through the
transistor 48 would otherwise exist inasmuch as the switch 54 is off when
the capacitor 46 is charging; but when the transistor 48 is conducting,
the resistor 58 keeps a low current through the transistor 48 since the
switch 54 is cut off.
The cyclic operation of the pulse generator 12 is explained as follows.
When the circuit is energized, a small amount of current will initially
flow through the resistor 36 and the capacitor 46 will be charged through
the potentiometer 40 and the resistor 38. Moreover, a circuit will be
completed through the transistor 48 to the ground line 32.
As the emitter voltage in the transistor 34 increases toward a firing
point, the voltage in the capacitor 46 will increase, and when the emitter
voltage does reach the firing point, the unijunction transistor 34 is
triggered to the "on" condition. The emitter voltage will then fall and
the capacitor 46 will then discharge so that the voltage potential at the
junction 59, namely the connection between the resistor 48 and the
capacitor 46, falls. This will, in turn, cause the transistor 48 to switch
to the off condition and cause a pulse to appear at the collector of the
transistor 48. The amplifier 52 will then conduct, producing an output
voltage at the output node 65.
The voltage at the output node will also be applied to the shorting switch
54 which effectively shorts out the resistor 58. Current will then flow
through the resistor 56 and the potentiometer 60, discharging the
capacitor 46 until the voltage on the base of the transistor 48 rises to a
point where the transistor 48 again conducts. At this time, the emitter
current to the unijunction transistor 34 drops, turning off the
unijunction transistor so the emitter voltage at the amplifier 52 will
drop, turning off the amplifier 52. The voltage at the output node 65 will
then fall to essentially zero.
The transistor 54 will then cease to conduct and the resistor 58 is then
switched into the circuit in series with the resistor 56 and the
potentiometer 60, thereby limiting the current flow through the base to
emitter of the transistor 48. The capacitor 46 will recharge through the
potentiometer 40 and the resistor 38, and the cycle will again start over.
The operation of the pulse generator 12 has been described somewhat in
connection with the description of the components of this circuit.
However, the following describes the operation of this generator in
greater detail. In this description, all voltages are given relative to
the negative conductor 32.
When the pulse generator circuit is initially energized by closing a switch
92 (hereinafter described), or at the end of the discharge cycle of the
capacitor 46 when the pulse generator has completed its pulse output, the
capacitor 46 is uncharged, and the unijunction transistor 34 is in a
low-conductance state in which almost no current flows through the
unijunction transistor 34. The capacitor 46 then begins to charge, with
the current flowing from the common positive conductor 30 through the
resistors 40 and 38, the capacitor 46 and the base to emitter circuit of
transistor 48 to the negative common conductor 32. Initially, both the
left and right sides of the capacitor 46 are at the same voltage, which is
the diode offset voltage of the transistor 48, typically approximately 0.5
volts. An additional current is supplied from the conductor 30 through the
potentiometer 60, the resistor 56, and the resistor 58, and from base to
emitter to transistor 48 to the negative conductor 30. This additional
current, while small, is sufficient to cause the transistor 48 to allow a
current to flow from conductor 30 through the load resistor 50, the
collector to emitter circuit of the transistor 48 and to the conductor 32,
so that the voltage at the input to the amplifier 52, which is the
connection between the transistor 48, the resistor 50 and the amplifier
52, is below the conduction threshold for the amplifier 52. No current
flows through the output emitter of the amplifier 52 so the voltage at the
output node 65 is essentially zero, and the shorting switch 54 also has
its input voltage below the threshold level and so no current flows
through the shorting switch 54. These conditions regarding the transistor
48, the shorting switch 54 and the amplifier 52 persist unchanged
throughout the charging cycle of the capacitor 46.
It is a property of the unijunction transistor 34 that some current flows
in the circuit from the conductor 30 through the resistor 36, the upper
base of the unijunction transistor 34, namely base-2, and thence to the
lower base (base-1) of the unijunction transistor and to conductor 30.
This current is greater when the unijunction transmitter fires than when
the unijunction transistor is in the low conductance state. However, in
the pulse generator described here, current through the resistor 36 is of
no significance except that proper choice of the value of resistor 36
provides excellent temperature compensation for the operation of the pulse
generator.
As the capacitor 46 charges, the voltage on the left side of the capacitor
46, and hence on the emitter of the unijunction transistor 34, rises until
the emitter of the unijunction transistor 34 reaches a fixed, reproducible
firing voltage, which is a predetermined portion of the voltage supplied
by the conductor 30. At this time, which is dependent primarily upon the
values of the capacitor 46 and the sum of resistors 38 and 40, the
unijunction transistor 34 abruptly begins to conduct, and the voltage at
the emitter of the unijunction transistor 34 and the left side of the
capacitor 46 falls to a low diode offset value, typically about 0.5 volts.
The voltage at the right side of the capacitor 46, and hence also the
junction 59 and the base of the transistor 48, falls by the same amount,
to a negative value. At this time, the transistor 48 ceases to conduct,
the input voltage to the amplifier 52 rises to the voltage of the
conductor 30, the amplifier 52 conducts, the voltage at the output
terminal 65 rises to a fixed value, and current flows through the resistor
55 to the input of the shorting switch 54, which shorts the resistor 58,
effectively connecting the resistor 56 to the junction 59. Current also
flows from the output terminal 65 through the resistor 63 and the
light-emitting diode 64, furnishing a visual indication that a pulse is
being generated, and flows from its output terminal 65 to the amplifier
section 14.
These conditions relative to the transistor 48, the amplifier 52, the
shorting switch 54, and the connections to output terminal 65 remain
constant for the duration of the capacitor discharge cycle, which is the
time during which the pulse generator actively delivers its output pulse.
The capacitor 46 is discharged by current flowing from conductor 30
through the potentiometer 60 and the resistor 56, the collector to emitter
output current of the shorting switch 54, capacitor 46, and the emitter to
lower base, i.e., base-1 of the unijunction transistor 34 to the conductor
32.
The capacitor continues to discharge until the voltage at the junction 59,
and hence at the base of transistor 48, reaches the threshold value at
which time the current at the junction 59 is diverted into the
base-to-emitter circuit of the transistor 48, and the current flow to the
emitter of unijunction transistor 34 drops abruptly. The unijunction
transistor 34 returns to the original low conduction state, the amplifier
52 is turned off, the shorting switch 54 ceases to conduct, the voltage at
the output terminal 65 falls to zero, and the charging cycle begins again.
In accordance with the above, it can be observed that the discharge time of
the capacitor 46 is related to a function of the resistance set by the
potentiometer 60 and is not at all related to the resistor 58. The
resistor 58 is only effectively included in the circuit when the capacitor
46 is not discharging. In essence, when the capacitor 46 does discharge,
the resistor 58 does not operate functionally in terms of controlling
charging and discharging with respect to the capacitor 46.
In the circuit of the present invention, the amount of current consumed
during the off time is very low and is therefore almost independent of
setting. The resistors 50 and 58 are active during the off time, and both
are of a high impedance. For example, the resistor 58 may have an
impedance of 40,000 ohms, and the resistor 50 may have an impedance of
50,000 ohms or more.
In accordance with this construction, it can be observed that the pulse
generator provides a stable frequency which is essentially independent of
on time controls, and only dependent on off time control. Moreover, the
circuit is not dependent on the amount of power drawn by the amplifier
section hereinafter described; and thus is independent of output control.
It should be understood, nevertheless, that the invention is still highly
effective and could operate by merely using fixed resistances in place of
the potentiometers 60 and 40. Furthermore, the circuit consumes a
negligible amount of power. By manipulating the potentiometer 40, it is
possible to control the pulse rate of the output signal. In like manner,
by controlling potentiometer 60, it is possible to control the pulse
width.
The amplifier output section is also more fully illustrated in FIG. 1 of
the drawings and comprises an NPN transistor 66 having its collector
connected to the base of a PNP transistor 68. The base of the transistor
66 is connected through the movable arm of a potentiometer 70 which, in
turn, receives the output of the pulse generator 12 from the node 65. The
emitter of the transistor 66 is connected through a resistor 72 to the
negative conductor 32 and also through a resistor 74 to the collector of
the transistor 68 and also to the base of the final power output NPN
transistor 75. The collector of the transistor 75, as well as the emitter
of the transistor 68, are connected to the positive conductor 30, in the
manner as illustrated in FIG. 1 of the drawings.
The transistor 66 and the transistor 68 serve as a high source impedance
amplifier section, and provide voltage and current amplification with
feedback. Moreover, these two transistors serve as a voltage amplifier
featuring high input impedance and low output impedance. The transistor 75
makes the output impedance very low.
The lower terminal of the resistive element forming part of the
potentiometer 70 is connected to the negative conductor 32 through a diode
71 to bias the amplifier section 14 input in order to provide linearity at
the potentiometer 70. In essence, this diode 71 could actually be a
resistor since it is designed to offset the base-to-emitter voltage in the
transistor 66.
The emitter of the transistor 75 is further connected through the primary
coil 76 of a transformer 78 and to the negative conductor 32. The primary
coil 76 of the transformer 78 generates a current in a secondary coil 80
of this transformer 78 which has a damping resistor 82 connected
thereacross and provides a pair of output terminals 84. The electrodes
mentioned above, which are designed for contact with the animal body, are
connected to these output terminals 84.
A neon bulb with a series connected current limiting resistor 88 is
connected across the terminals 84 to provide indication of the condition
of the battery 16 when no load is connected to the output terminals 84. As
the battery condition thus deteriorates, a greater voltage position on the
potentiometer 70 will be required to energize the bulb 86. Thus, if the
battery 16 has been seriously discharged, the neon bulb 86 will not be
energized to emit light. It should also be observed that the neon bulb 86
is also mounted on the control panel C, in the manner as illustrated in
FIG. 2 of the drawings.
The potentiometer 70 also provides for control of the output current and
will therefore be provided with a control knob 90 which is suitably
mounted on the control panel C. The exact arrangement for connecting the
various control knobs 42, 62 and 90 to their associated components is
conventional, and therefore has neither been illustrated nor described in
any further detail herein. In this respect, it should be observed that the
potentiometer 70 is also physically connected to a main power switch 92
which is located in the negative conductor 32 and serves to energize or
de-energize the entire stimulator A. By physically connecting the switch
92 to the potentiometer 70, it is possible to obviate the problems which
could otherwise result from surges when the switch 92 is initially turned
to the "on" condition if the electrodes connected to the output terminals
84 were attached to the body of a patient. The switch 92 can also be
suitably mounted on the control panel C. In actual practice, the switch 92
would by physically incorporated in the potentiometer and would be
operable by the shaft of the potentiometer 70.
By using feedback to the arrangement of the transistors 66 and 68, the
pulse voltage input at the coil 76 is proportional to the voltage
established by the potentiometer 70. The feedback at the transistor 66 is
based on the current on the collector being about eighty times greater
than the current at the base thereof.
The resistors 74 and 72 act as a voltage divider such that when voltage at
the collector of the transistor 68 is greater than that at the emitter of
the transistor 66, current flows through the resistors 74 and 72 which
will maintain current input to the transistor 66 at a very low level, thus
producing a high impedance at the base of the transistor 66.
The amplifier section 14 is actually a two-stage amplifier with the
transistors 66 and 68 constituting the first stage and the transistor 75
constituting the second stage. The stage comprised of the transistors 66
and 68 actually functions as a current and voltage amplifier with a
feedback such that the gain thereof is almost completely dependent on the
values of the resistors 72 and 74. The transistor 75 receives an output
from the collector of the transistor 68 and the current passing through
the resistor 74 less that amount used in the feedback path through the
resistor 74. This emitter follower configuration employing transistor 75
provides a high current amplification to match the low input impedance of
the coil 76.
One of the unique aspects of the amplifier output section 14, or so-called
"amplifier output stage", is that this amplifier output stage 14 only
draws current in proportion to the setting of the output power knob,
thereby lending to a highly efficient operation. Moreover, by placing the
output control potentiometer where it is in close relation to the
transformer 78 and by utilizing the resistor 82, the transformer 78 is
well damped over its entire range. Furthermore, this amplifier is designed
so that it is an excellent impedance match for the human body as well as
most warm-blooded animal bodies having a central nervous system to provide
transcutaneous stimulation. It can be observed that if the impedance was
too high, any movement of the electrode would create a burning sensation
on the animal.
The transistors 66 and 68 actually constitute a voltage-current amplifier
with feedback to raise the maximum voltage available to the base of the
transistor 75 close to the available voltage of the power supply. The
voltage at the output of the pulse generator 12 is reduced by over a
one-volt level due partially to the characteristics of the transistors of
the amplifier 52. The ratio of the values of the resistor 74 plus the
value of the resistor 72 as divided by the value of the resistor 72 is
designed to restore any voltage loss.
In accordance with the above, it can be observed that the pulse shape at
the output terminals 84 is independent of all three settings of the
generator A. In addition, all three pulse control functions are
independent of each other. The output waveform has no D.C. component and,
therefore, any electrophoretic effects are minimized. Since the amplifier
section has no effect on the pulse generator, it is possible to provide
more than one parallel amplifier section in cases where more than two
electrodes are desired to be used. These additional amplifier sections
would be connected to conductors 30 and 32, the pulse generator output at
the node 65 and could, in addition, contain on-off switches in parallel
with the switch 92.
Thus there has been illustrated and described a novel electrically operable
stimulator for generating and applying electrical stimuli signals to an
animal body to accomplish various beneficial physiological results
including the control of pain and which therefore fulfills all of the
objects and advantages sought therefor. It should be understood that many
changes, modifications and other uses and application may be made by those
skilled in the art based on the specification and the accompanying
drawings. Therefore, any and all such changes, modifications and other
uses and applications which do not depart from the nature and spirit of
the invention are deemed to be covered by the invention which is limited
only by the following claims.
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