US3728501A - Touch sensitive electronic switch - Google Patents

Abstract

A touch sensitive electronic switch which has no moving parts and is actuated by the skin resistance of an operator causing a lowering of D.C. resistance across the face of the switch is disclosed. The electronic switch, in the preferred embodiment shown, includes three electrodes spaced and arranged with respect to each other upon an insulator. The second electrode is laterally spaced and insulated from the first electrode and arranged around and about the first electrode with the level of the top surface of the second electrode rising above the level of the top surface of the first electrode. The third electrode is laterally spaced and insulated from one electrode and vertically spaced from the other electrode to provide a conductive electrical shielding electrode between the first and second electrodes. The first and second electrodes are exposed to the finger of an operator upon the top surface of the insulator in a manner that the operator''s finger bridging between the fist and second electrodes allows a direct current path to be set up laterally between the first electrode and the second electrode to thereby provide an activation of the switch through a lowering of the D.C. resistance across the face of the switch. When the operator''s finger is removed, the shielding effect of the third electrode prevents any leakage currents from flowing between the first electrode and the second electrode and establishing such a direct current path.

Description

United States Patent i 91 Larson et al.

[451 Apr. 17, 1973 TOUCH SENSITIVE ELECTRONIC SWITCH I [75] Inventors: Willis A. Larson, Wayzata; Stephen 7 R. Tell, Bloomington, both of Minn.

[73] Assignee: Magic Dot, Inc., Minneapolis, Minn.

[22] Filed: Mar. 16, 1972 21 Appl. No.: 235,373

52 us. Cl ..200/'s2, 200/010. 2

[51] lnt. Cl. ..l-l01h 35/00 [58] Fieldot Search ..200/DlG. 2, DIG. l,

[ 56] References Cited UNITED STATES PATENTS 3,207,905 9/1965 Bray ..200/l59 R Primary Examiner-Herman J. l-lohauser Att0rneyWicks and Nemer [57] ABSTRACT A touch sensitive electronic switch which has no moving parts and is actuated by the skin resistance of an operator causing a lowering of DC. resistance across the face of the switch is disclosed. The electronic switch, in the preferred embodiment shown, includes three electrodes spaced and arranged with respect to each other upon an insulator. The second electrode is laterally spaced and insulated from the first electrode and arranged around and about the first electrode with the level of the top surface of the second electrode rising above the level of the top surface of the first electrode. The third electrode is laterally spaced and insulated from one electrode and vertically spaced from the other electrode to provide a conductive electrical shielding electrode between the first and second electrodes. The first andsecond electrodes are exposed to the finger of an operator upon the top surface of the insulator in a manner that the operators finger bridging between the fist and second electrodes allows a direct current path to be set up laterally between the first electrode and the second electrode to thereby provide an activation of the switch through a lowering of the DC. resistance across the face of the switch. When the operator's finger is removed, the shielding effect of the third electrode prevents any leakage currents from flowing between the first electrode and the second electrode and establishing such a direct current path.

4 Claim, 5 Drawing SHEET 2 []F 2 TOUCH SENSITIVE ELECTRONIC SWITCH CROSS REFERENCES This invention is an improvement upon the subject matter disclosed and claimed in an application for patent filed in the name of Willis A. Larson on July 9, I971, Ser. No. 161,948, which is a continuation of application Ser. No. 865,760, filed Oct. 13, 1969 (hereinafter referred to as the original application). The present application is further an improvement upon the subject matter disclosed and a companion application to the applications for patent filed on Nov. 16,

1971 by Willis A. Larson and Raymond M. Warner,

J r., Ser. No. 199,227, entitled Composite D.C. Amplifier For Use With A Touch Sensitive Electronic Switch; Willis A. Larson, Ser. No. 199,226, entitled Touch Sensitive Electronic Switch;" Willis A. Larson and Arthur Kimmell, Ser. No. 199,384, entitled Touch Sensitive Electronic Switch; and Willis A. Larson, Ser. No. 199,195, entitled Touch Sensitive Electronic Switch (hereinafter referred to as the companion applications).

BACKGROUND This invention relates generally to electronic switching and more specifically to a touch sensitive electronic switch which has no moving parts and is actuated by the skin resistance of an operator lowering the DC. resistance across the face of the switch.

In the above referenced to original and companion applications, the problem of avoiding current leakage between the operative electrodes of a touch sensitive electronic switch were discussed and solutions provided. The present invention offers another solution which eliminates the problem of undesired activation due to current leakage between the operative electrodes of the electronic switch.

SUMMARY In summary, a preferred embodiment of the present invention eliminates the problem of undesired activation due to current leakage between the operative electrodes of the electronic switch by providing, in the preferred embodiment, a first electrode immovably arranged upon an insulator and a second electrode also immovably arranged upon an insulator. The second electrode is further arranged around and about and laterally spaced and insulated from the first electrode. A third electrode is also immovably arranged upon the insulator in a spaced and insulated relationship with both the first and second electrodes and laterally spaced from the first electrode and vertically spaced from the second electrode. The first and second electrodes are exposed to the finger of an operator upon the top surface of the insulating media in a manner that the operators finger bridging between the second electrode and the first electrode allows a direct current path to be established laterally between the second and the first electrodes to thereby provide an actuation of the switch through a lowering of the D. C. resistance across the face of the switch. When the operators finger is removed, the shielding effect of the interposed third electrode prevents any leakage currents from flowing between the second electrode and the first electrode and establishing such a direct current path.

It is thus a broad object of the present invention to provide a novel touch sensitive electronic switch.

It is a further object of the present invention to provide such a switch having extremely low leakage currents between electrodes to thus maintain the integrity of the switch in the OFF condition.

It is a further object of the present invention to provide such a switch where an electrode acts as a shield to prevent a flow of leakage current between other electrodes.

It is a further object of the present invention to provide such a switch which may be more easily fabricated than switches known heretofore.

These and further objects and advantages of the present invention, including those set out in the original and companion applications, will become clearer in the light of the following detailed description of an illustrative embodiment of this invention described in connection with the drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a top view of a preferred embodiment of a touch sensitive electronic switch according to the present invention.

FIG. 2 shows a cross-sectional view of a touch sensitive electronic switch according to section line 2-2 in FIG. 1.

FIGS. 3 and 4 show simplified top views of various components of the touch sensitive electronic switch according to the present invention which are useful in explaining its fabrication.

FIG. 5 shows a schematic representation of electronic circuitry for use with the touch sensitive electronic switch of the present invention.

Where used in the various Figures of the drawing, the same numerals designate the same or similar parts. Furthermore, when the terms right, left, front, back, vertical," horizontal," right edge, left edge, right side, left side, top, bottom, and similar terms are used herein, it should be understood that these terms have reference only to the structure as shown in the drawings as they would appear to person viewing the drawings, and are utilized only to facilitate describing the present invention.

DESCRIPTION In FIGS. 1 and 2, a touch sensitive electronic switch, generally designated 30, is shown.Switch 30 includes a square of insulating media or insulatingmaterial 38 which can be conventional printed-circuit board material.Insulator 38 includes a flat or planar top surface orface 39 and a bottom surface orface 40.

Insulator 38 supports supply conductor orelectrode 42 including a digitated array of nine fingers commonly designated 44 which extend across the top face orswitch face 39 ofinsulator 38 from top to bottom as viewed in FIG. 1. Aconductive trace 48 positioned at the top edge ofswitch face 39 perpendicularly to thesupply fingers 44 interconnects the supply fingers to formsupply electrode 42.

Insulator 38 also supports an input conductor orelectrode 50 which includes a digitated array of eight fingers, commonly referred to as 52, which extends across theswitch face 39 from bottom totop as viewed in F IG. 1.Input fingers 52 are arranged betweensupply fingers 44 and in particular are arranged with one input finger positioned between each two supply fingers. A conductive trace 56 arranged on the bottom edge ofswitch face 39, as viewed in FIG. 1, perpendicularly to theinput fingers 52 interconnects the input fingers to forminput electrode 50.

Thus,supply electrode 42 andinput electrode 50 take the form of an array of interlaced or interdigitated components including fingers extending from an edge ofswitch face 39 towards one another.

Insulator 38 also supports a reference, common, or ground conductor orelectrode 58.Ground 58 also includes a digitated array of nine fingers arranged vertically below and in the same configuration assupply fingers 44. Aconductive trace 60 forms a rightward extension of theright-most finger 59 of ground electrode, as shown in FIGS. 1 and 2, to thus extend to the rightmost edge ofswitch face 39.Ground electrode 58 is insulated fromsupply electrode 42 by aninsulator layer 61, such as mylar, whichinsulator 61 is formed in the pattern ofsupply electrode 42 andground electrode 58, as will be explained further hereinafter.

In fabricating the preferred embodiment ofelectronic switch 30,top surface 39 ofinsulator 38 is first entirely clad with a conductor, such as one ounce nickel, in a fashion conventional for the fabrication of standard printed-circuit boards. In fact, a multitude of switches such asswitch 30 shown in the figures may be fabricated simultaneously and later separated. In this manner, not only can multiple and thus rapid fabrication be had, but conventional registration techniques such as pins projecting from ajig can control the registration of the various layers as will be explained hereinafter.

Assuming multiple fabrication and a projecting pin registration system, a conventional photographic resist material is applied over the entire surface of the conductor applied totop surface 39 ofinsulator 38; the photographic resist material is photographically exposed in the pattern ofinput electrode 50 andground electrode 58; andinsulator 38 is removed from the photographic jig, and the conductive coating is conventially etched to form the pattern ofinput electrode 50 andground electrode 58. FIG. 3 shows switch 30 of the present invention at this stage of fabrication with the number of fingers shown reduced for simplication.

The next fabrication step uses a sheet of insulation material, such as mylar, completely coated upon one side with a conductive material such as one ounce nickel in a manner to bond the nickel to the mylar. A sheet of adhesive is placed over the partially completedswitch 30 of the present invention such as is shown in FIG. 3, and the mylar and nickel combination sheet is placed over the adhesive with the nickel side vertically upward. The mylar and nickel combined sheet is then firmly bonded to the partially completedswitch 30. Then, a photographic resist material is applied to the exposed nickel surface, and the array ofswitches 30 of the present invention is returned to the photographic jig and realigned upon the conventional projecting pins. This allows the substantially exact registration of thesupply electrodes 42 overground electrode 58 as will now be explained.

Next, the exposed nickel surface is photographically exposed in the pattern ofsupply electrode 42, which is identical to the pattern ofground electrode 58 with the exception of the elimination ofconducive trace 60. Thesupply electrode 42 is then conventionally etched from the exposed nickel material uponmylar sheet 61 to formsupply electrode 42, such as is shown in FIG. 4.

Next, with thesupply electrode 42 forming the resist, portions ofmylar sheet 61 not protected bysupply electrode 42 are dissolved by a solvent to leave themylar insulator 61 betweensupply electrode 42 andground electrode 58.

Thus, digitated pattern ofground electrode 58, portions ofmylar sheet 61, andsupply electrode 42 may be fabricated in a vertical arrangement of substantially identical registration withmylar sheet 61 insulatingsupply electrode 42 fromground electrode 58.

The overall arrangement of the threeelectrodes 42, 50, and 58 of theelectronic switch 30 of the present invention may now be explained. As is shown in the Figures,input electrode 50 is laterally immovably arranged withinsulator 38, with a top surface ofinput electrode 50 exposed to the finger of an operator upon the top surface ofinsulator 38.Supply electrode 42 is also laterally immovably arranged with theinsulator 38 and withinput electrode 50, and is arranged laterally around and about, spaced, and insulated frominput electrode 50 in a manner to expose the top surface ofsupply electrode 42 to the finger of the operator upon the top surface of its surrounding insulating material. The level of the top surface ofsupply electrode 42 is further arranged above the level of the top surface ofinput electrode 50 in a manner that the finger of the operator touchessupply electrode 42 before contact is made between the finger andinput electrode 50 to thereby allow good contact of the operators finger withsupply electrode 42 before contact is made withinput electrode 50 and thereby allow the harmless grounding of the usual alternating voltage induced from an external source into an operators body as also explained in the original and companion applications. This arrangement of electrodes also allows a direct current path to be set up laterally between theinput electrode 50 and thesupply electrode 42 as soon as the finger of the operator touches theinput electrode 50.

Ground electrode 58 is also laterally immovably arranged with its surrounding insulating media and with the input andsupply electrodes 42 and 50.Ground electrode 58 is further arranged electrically between the input andsupply electrodes 50 and 42 and is insulated from both electrodes as a conductive electrical shield electrode allowing leakage current which could otherwise flow between theinput electrode 50 and thesupply electrode 42 to be conducted to a reference point through theground electrode 58 to thus aid in preventing the flow of leakage current betweeninput electrode 50 andsupply electrode 42 which would otherwise tend to set up a non-actuated direct current path from the input electrode to the supply electrode. Thus, a non-actuated direct current path between the electrodes is one such as may be caused by leakage current in the switch and not by a touching of the switch face by the operators finger or other external cause.

Wrap-around connections betweenconductive traces 60, 48, and 56 on thetop side 39 ofinsulator 38 to other conductors on thebottom side 40 ofinsulator 38 may also be fabricated as described in application Ser. No. 199,195, or plated through holes, or other connection may be fabricated to allow electrical connection betweenconductive traces 60, 56, and 48 on thetop face 39 ofinsulator 38 and conductors onbottom face 40 ofinsulator 38. It is to be noted that the height, spacing and other requirements of face configurations according to the original and companion applications can thus be adhered to by theswitch 30 of the present invention. Further, usingswitch 30 as described herein, the problems described in application Ser. No. 199,195 in allowing an operators finger to contact supply andinput electrodes 42 and 50 andground electrode 58 may be completely eliminated sinceground electrode 58 is beneath one of theelectrodes 42 and 50 rather than laterally beside theelectrodes 42 and 50.

Further, because of the positioning ofground electrode 58, the critical nature of the lateral spacing betweenelectrodes 42 and 50 can be reduced and they may be more easily fabricated.

Now that the arrangement and fabrication ofswitch 30 of the present invention has been explained, it will be clear to those skilled in the art that it may be connected with electronic circuitry such as that shown in the original and companion applications, or other circuitry. For clarity, the manner of connection to the circuitry shown in the companion applications is set out below in the description of FIG. 5.

In FIG. 5, switchface 39 is shown in schematic form withsupply electrode 42,input electrode 50, andground electrode 58 also schematically represented.

Input electrode 50 is connected by a lead 71 to input 72 of a composite amplifier, generally designated 74, includingoutputs 76 and 78.Output 76 is connected to afirst terminal 80 of a DC. voltage source or supply throughresistor 82 representing an electrical load.Supply terminal 80 is also connected to asupply electrode 42 through alead 84.Output 78 is connected to asecond supply terminal 86 of the DC. voltage supply through aconnection 88.Terminal 86 is further connected to groundelectrode 58 by aconnection 90. The DC. voltage source, not specifically shown, includes the first andsecond terminals 80 and 86, and provides direct current toamplifier 74. As shown in FIG. 5,terminal 86 is a common, ground, or reference terminal, and terminal 80 is of a positive DC. voltage differing from the voltage at 86.

Input 72 tocomposite amplifier 74 is connected to input 92 of a first amplifier 94 through abuffer amplifier 96. First amplifier 94 further includes two outputs in the form ofjunction points 98 and 100. A current limitingresistor 102 is connected betweenjunction point 98 andsupply terminal 80, and aleakage prevention resistor 104 is connected betweenjunction point 100 andsupply terminal 86.Junction point 100 is further connected to aninput junction point 106 of asecond amplifier 108 through a lead 1 10.Second amplifier 108 includes anoutput junction point 112 connected to aninput junction point 114 of athird amplifier 116 by alead 118 and to supply terminal 86 by anotherleakage prevention resistor 119.Second amplifier 108 further includesoutput junction point 120 connected to supply terminal 80 by a current limiting and parasiticoscillation reducing resistor 122.Third amplifier 116 includes anoutput junction point 124 connected tooutput 76 ofamplifier 74 and anoutput junction point 126 connected tooutput 78 ofamplifier 74.

Buffer amplifier 96 includes a base current limitingresistor 128 connected betweeninput 72 and the base of anNPN transistor 130.Transistor 130 has its emitter connected to supplyterminal 86 and its collector connected to input function point 92 of first amplifier 94.

First amplifier 94 includesPNP transistor 132 having its base connected to junction point 92, its emitter connected tojunction point 98, and its collector connected tojunction point 100.

Second amplifier 108 includes two amplifying stages in the form ofNPN transistors 134 and 136 connected in a Darlington type arrangement.First Darlington transistor 134 has a base connected tojunction point 106, a collector connected to supply terminal 80 through another current limiting andoscillation reducing resistor 138. The emitter oftransistor 134 provides an output current to the base of thesecond Darlington transistor 136 throughjunction point 140.Second Darlington transistor 136 has its emitter connected to junction point 1 12, and its collector connected tojunction point 120.

Aleakage prevention resistor 142 is connected between junction point andsupply terminal 86.

Third amplifier 116 includesNPN transistor 144 with its base connected tojunction point 114, its collector connected tojunction point 124, and its emitter connected tojunction point 126.

OPERATION Generally, in operating the touch sensitiveelectronic switch 30 shown in the Figures, the finger of an operator is placed upon theswitch face 39, for example as shown by thefinger portion 144 shown in FIG. 2. The electrical skin resistance of the operator causes a direct current path to be set up betweeninput electrode 50 andsupply electrode 42 to thus cause a small current to flow between these electrodes. The current flowing is generally in the nanoampere range (30-300 nanoamperes) with normal skin resistances and supply voltages of approximately 5 volts. This D. C. input current is amplified by the various stages ofcomposite amplifier 74 shown in FIG. 5 to a point whereoutput transistor 144 saturates and approximate an electronic switch in the closed of ON condition to theelectrical load 82 also connected acrosssupply terminals 80 and 86. When the operator'sfinger 144 is removed fromswitch 30, the characteristics of the switch prevent input current from reachinginput 72 ofcomposite amplifier 74 and rapidly render the amplifying stages to and includingoutput transistor 144 nonconducting. Thus, with the operators finger removed fromswitch 30,composite amplifier 74 appears as an electrical switch in an open of OFF condition to load 82, and no current is allowed to flow in the electrical load.

In particular, groundingelectrode 58 is connected to a reference point within directcurrent amplifier 74. That is,ground electrode 58 is connected to the lowest potential point in the electronic circuit to which theinput electrode 50 andsupply electrode 42 are connected. By its interposition between theinput electrode 50 and thesupply electrode 42, leakage current attempting to flow between theinput electrode 50 and thesupply electrode 42 first encounters the conductive electrical shielding effect ofground electrode 58 and is conducted to such reference or ground. Thus, the electrical shielding ofground electrode 58 prevents a flow of leakage current between the input electrode without actuation of the switch by the finger of an operator, which is an undesired actuation of theelectronic switch 30.

It is not necessary, however, thatelectrode 58 be connected to the ground point in the D. C. amplifier.Electrode 58 may be connected to any potential supply of a voltage below that of the supply voltage to the amplifier and yet provide some shielding. It is apparent, however, that the maximum shielding is provided whenelectrode 58 is in fact connected to the reference, ground, or common point of the D. C. amplifier to which switch 30 is connected.

It is to be noted that actuation of theswitch 30 of the present invention is made without moving parts, aside from movement of the operators finger. That is, each of thesupply electrode 42 andinput electrode 50 is laterally immovably attached toinsulator 38. Laterally immovably attached for the purposes of this invention is defined as where the input and supply electrodes are fixed with respect to each other in a manner to prevent the input electrode from coming into direct electrical contact with the supply electrode. Either electrode may be made vertically movable, as by using a soft or spongy material or springs to give the effect or feeling of vertical movement to an operators finger. Other means for effecting this illusion of vertical movement upon actuation will be envisioned by those skilled in the art.

Thus, since the invention disclosed herein may be embodied in other specific forms without departing from the spirit of general characteristics thereof, some of which forms have been indicated, the embodiment described herein is to be considered in all respects illustrative and not restrictive. The scope of the invention is indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

What is claimed is:

1. Electronic switch apparatus operable by the lateral bridging of the switch electrodes by the skin resistance of an operator, comprising in combination: insulating media having a top surface; first electrode means laterally immovably arranged with the insulating media with the top surface of the first electrode exposed to the finger of an operator upon the top surface of the insulating media; second electrode means laterally immovably arranged with the insulating media and the first electrode laterally around and about, spaced, and insulated from the first electrode with the top surface of the second electrode exposed to the finger of an operator upon the top surface of the insulating media laterally from the first electrode and with the top surface of the second electrode arranged above the level of the top surface of the first electride in a manner that the finger of an operator touches the second electrode before contact is made between the finger and the first electrode to thereby allow good contact of the operator's finger with the second electrode before contact is made witlithe first electrode and thereby allow the harmless discharge of voltage in an operators bod and allow a direct current path to be set up laterally etween the first electrode and the second electrode as soon as the finger of the operator touches the first electrode; third electrode means laterally immovably arranged with the insulating media, with the first electrode, and with the second electrode, electrically between the first and second electrodes, spaced vertically and insulated from one of the first and second electrodes and laterally spaced and insulated from the other of the first and second electrodes as a conductive electrical shielding electrode allowing leakage current flowing between the first electrode and the second electrode to be conducted to a. reference point to aid in preventing a fiow of leakage current between the first electrode and second electrode tending to set up a non-actuated direct current path from the first electrode to the second electrode: first means for providing an electrical connection to the first electrode; second means for providing an electrical connection to the second electrode; and third means for providing an electrical connection to the third electrode.

2. The electronic switch apparatus of claim 1, wherein the first connection means comprises means for providing an electrical connection between the first electrode and the input of a D. C. amplifier.

3. The electronic switch apparatus ofclaim 2, wherein'the third connection means comprises means for providing an electrical connection between the third electrode and a reference point within the D. C. amplifier.

4. The electronic switch apparatus of claim 3, wherein the second connection means comprises means for providing an electrical connection between the second electrode and a means for supplying D. C. voltage to the D. C. amplifier.

THE UNITED STATES PATENT O'F-FICE EEBEEEEEAEE 2E QQEEEQEEQE Patent No. 3,728,501 Dated April 17, 1973 Willis A. Larson Stephen R. Tell It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

7 In the ABSTRACT, line 17, cancel "fist" and substitute therefor --first-.

Column 1, line 28, cancel "referenced" and substitute therefor -referred-.L

Column 6,line 44, "approximate" should read -approximates--; v i p Column-'6, line 45, after "the closed" cancel "of" and substitute --or--;

I Column 6, line 46, delete "also"; cancel "across V supply" and substitute "betweencancel "86." and substitute -76.--;

Column 6 line 54, after "open", cancel "of" and substitute --or--; v 1

Column 6,line 59, after."e1ectronic circuit"insert 74--. 1

Claim 1, column 8, line 8, "electride" should read -electrode--; p

Column 8, insert the following claim:

--5. The electronic switch apparatus of claim 1 v wherein the third electrode is arranged immediately below the second electrode.--.

Signed and sealed this 8th. day of January 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer 7 "Acting Commissioner of Patents THE UNITED STATES PATENT OFFICE CERTIFICATE 9E EQBEEEZZQE Patent No. 3,728,501 Dated April 17, 1973 Willis A. Larson Stephen R. Tell It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

In the ABSTRACT, line 1'], cancel "fist" and substitute therefor --first--. 7

Column 1, line 28, cancel "referenced" and substitute therefor -referred--.

Column 6,line 44, "approximate" should read --approximates-;

Column 6, line 45, after "the closed" cancel "of" and substitute --or--;

Column 6, line 46, delete "also"; cancel "across supply" and substitute -between-; cancel "86." and substitute Column v6, line 54, after "open", cancel "of" and substitute -or--;

Column 6,line 59, after "electronic circuit" insert Claim 1, column 8, line 8, "electride" should read -electrode-w Column 8, insert the following claim:

--5. The electronic switch apparatus of claim 1, wherein the third electrode is arranged immediately below the second electrode.--.

Signed and sealed this 8th day of January- 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents

Claims (4)

1. Electronic switch apparatus operable by the lateral bridging of the switch electrodes by the skin resistance of an operator, comprising in combination: insulating media having a top surface; first electrode means laterally immovably arranged with the insulating media with the top surface of the first electrode exposed to the finger of an operator upon the top surface of the insulating media; second electrode means laterally immovably arranged with the insulating media and the first electrode laterally around and about, spaced, and insulated from the first electrode with the top surface of the second electrode exposed to the finger of an operator upon the top surface of the insulating media laterally from the first electrode and with the top surface of the second electrode arranged above the level of the top surface of the first electride in a manner that the finger of an operator touches the second electrode before contact is made between the finger and the first electrode to thereby allow good contact of the operator''s finger with the second electrode before contact is made with the first electrode and thereby allow the harmless discharge of voltage in an operator''s body and allow a direct current path to be set up laterally between the first electrode and the second electrode as soon as the finger of the operator touches the first electrode; third electrode means laterally immovably arranged with the insulating media, with the first electrode, and with the second electrode, electrically between the first and second electrodes, spaced vertically and insulated from one of the first and second electrodes and laterally spaced and insulated from the other of the first and second electrodes as a conductive electrical shielding electrode allowing leakage current flowing between the first electrode and the second electrode to be conducted to a reference point to aid in preventing a flow of leakage current between the first electrode and second electrode tending to set up a non-actuated direct current path from the first electrode to the second electrode: first means for providing an electrical connection to the first electrode; second means for providing an electrical connection to the second electrode; and third means for providing an electrical connection to the third electrode.

2. The electronic switch apparatus of claim 1, wherein the first connection means comprises means for providing an electrical connection between the first electrode and the input of a D. C. amplifier.

3. The electronic switch apparatus of claim 2, wherein the third connection means comprises means for providing an electrical connection between the third electrode and a reference point within the D. C. amplifier.

4. The electronic switch apparatus of claim 3, wherein the second connection means comprises means for providing an electrical connection between the second electrode and a means for supplying D. C. voltage to the D. C. amplifier.

Images