4,731,548
`{11] Patent Number:
`United States Patent 5
`Ingraham
`(45) Date of Patent: Mar. 15, 1988
`
`
`[54] TOUCH CONTROL SWITCH CIRCUIT
`;
`[75]
`Inventor: Ronald D. Ingraham, Quincy, Mich.
`on.
`.
`.
`[73] Assignee: Narron Corporation, Reed City,
`Ich.
`[21] Appl. No.: 913,084
`"
`[22] Filed:
`Sep. 29, 1986
`PSU]
`Trnt, C04 ccccccssccccscscsscesesssssecessssseuen HO1H 35/00
`[52] U.S. Che seessesesessssssssssssssssssscsssses 307/116; 307/308;
`307/632; 200/DIG. 1
`[58] Field of Search............... 307/116, 125, 252, 308;
`315/34, 74, 208, 246, 362; 318/345, 446;
`323/19, 24; 328/5;.200/DIG.1
`References Cited
`U.S. PATENT DOCUMENTS
`3,549,909 12/1970 Adelson ét al.
`......esseseseceees 307/252
`3,641,410
`2/1972 Vogelsberg «1... 318/345
`
`31666988
`5/1972 Bellswe
`Gor/itex
`
`
`3,899,713
`8/1975 Barkan etal.
`* 307/308 X
`
`3,919,596 11/1975 Bellis ....sssocccsssseeeceeeeseen 307/308 X
`
`3,965,465
`6/1976 Alexander.......ccsseseee 340/274 R
`3,984,757 10/1976 Gottet al.
`...
`.. 315/246 X
`
`4,016,453 4/1977 Moennig ..
`- 307/308 X
`
`4,031,408
`6/1977 Holz ou...
`sscsccsssssescsseressenssees 307/116
`4,101,805
`7/1978 Stone...
`307/308 X
`
`4,119,864 10/1978 Petrizio
`......cccscssssscessseeeess 307/116
`
`4,152,629
`5/1979 Rapp ....cccccesesesessenesereeee 315/362
`
`[56]
`
`6/1979 Semk cesccssesessssstssssseeseee 307/116 X
`4,159,473
`
`7/1980) WEFT cessssssssssssssesessesesseen 307/116
`4,210,822
`7/1980 Deavenport etal........... 307/308 X
`4,211,959
`
`4,213,061 7/1980 Commer vscstsssscssesssssssenesen 307/116
`«.. 307/116 X
`1/1981 Chiang ..
`4,246,533
`4/1981 Wern .....
`we 307/116 X
`4,264,831
`
`9/1981 Wern ........
`we 307/116
`4,289,972
`
`4,289,980 9/1981 McLaughlin....
`ve 307/308
`4,308,443 12/1981 Tuckeret al.
`...
`wu 307/116 X
`
`2360937 ioe eonGhabreneJOT
`Primary Examiner—William M. Shoop,Jr.
`Assistant Examiner—Sharon D. Logan
`Attorney, Agent, or Firm—Price, Heneveld, Cooper,
`DeWitt & Litton
`ABSTRACT
`(57]
`in
`A touch controlled electronic switching circuit
`which the body capacitance of the person actuating the
`device is coupledin series with currentlimiting resistors
`284 @ Capacitor with the junction coupled to a logic
`circuit whichresponds theretoto provide a direct cur-
`‘Tent controlsignal. The logic circuit has an output cou-
`pled to the gate terminal of a Triac coupled to a load for
`selectively applying current to said load during both
`—_half-cycles of each cycle ofthe line voltage supplied to
`the Triac and load.
`
`19 Claims, 1 Drawing Figure
`
` 40
`
`
`NEUTRAL
`
`NS
`VAC
`
`1
`
`APPLE 1016
`
`1
`
`APPLE 1016
`
`

`

`U.S. Patent
`
`Mar. 15, 1988
`
`4,731,548
`
`TWULNAN
`
`Ov
`
`
`
`iStd
`
`9p
`
`2
`
`

`

`1
`
`TOUCH CONTROL SWITCH CIRCUIT
`
`BACKGROUNDOF THE INVENTION
`
`4,731,548
`
`2
`ing description thereof together with reference to the
`accompanying drawing in which:
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG.1 is an electrical circuit diagram in schematic
`form of the system of the present invention.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The present invention relates to an electrical circuit
`and particularly to a touch controlled electrical switch-
`ing circuit.
`There exists a variety of electrical switching circuits
`which respond to a person’s touch on a touch pad
`which can be in the form of a lamp base or a specific
`surface area of an electrical appliance to be actuated.
`Suchcircuits represent a convenient manner by which a
`consumer can easily operate appliances without the
`need for manually actuating a conventional
`toggle,
`push-button or other type switch. Touch controlled
`electrical switching circuits have becomeincreasingly
`popular; for example, in use in controlling table lamps,
`floor lamps andthelike although they haveother appli-
`cations as well. U.S. Pat. Nos. 4,119,864 and 4,360,737
`are representative of existing touch controlled switch
`circuits. Typically, such circuits employ the human
`body as an antenna for picking up 60 Hz radiation exist-
`ing in an environmentby virtue of the line frequency
`powerin the building andutilizes the induced voltage as
`a trigger signal for controlling the touch controlled
`electrical circuit. Such systems, however, can suffer
`from erratic operation due to variations in the nature of
`the ambient 60 Hzfield and the physiological makeup of
`the person utilizing the system. Also the prior art sys-
`temstypically utilize a pulse control for controlling a
`solid-state switch such as a Triac to be conductive only
`during a portion of each cycle of operation of the AC
`power supply thereby reducing the efficiency of such
`systems.
`.
`
`SUMMARY OF THE PRESENT INVENTION
`
`In FIG. 1, the electrical circuit 10 for providing a
`touch controlled electrical switch is shown and includes
`a touch plate 12 as its control input element which is
`touched by a person for actuation of the electrical
`switching circuit. The switching circuit includes a bidi-
`rectional solid-state switch 20 such as a Triac having
`one power terminal 21 coupled to the one side of the
`typically 115 volt 60 Hz AC supply line 30 andits re-
`maining powerterminal 22 coupled to one terminal 24
`of a load 26 to be controlled. The remaining terminal 27
`ofthe load is coupled to the line neutral conductor 40.
`A series spike suppression resistor 25 and capacitor 28
`are coupled across the Triac 20 to preventfalse turn-on.
`The circuit 10 may include a plug which connects
`directly into, for example, a wall socket to provide
`connections for lines 30 and 40 to the building’s wiring
`system and a socket for receiving terminals 24 and 27 of
`a load 26 such as a lamp to be controlled. The circuit 10
`may be built directly into, for example, a base or other
`mechanical structure associated with a lamp or other
`appliance and wired directly as shown in FIG. 1 with a
`plug for plugging directly into a power outlet of the
`building’s power supply system.
`The touch plate typically is a conductive element
`whichis insulated from the remaining body orthe like
`of a lamp base or other appliance andis in a location
`readily accessible by the user. The user’s body includes
`a capacitance portion represented by capacitor 42 in
`FIG. 1 which may range in a typical person from be-
`The system of the present invention provides an im-
`tween 100.to 300 picofarads. When a person touches
`proved touch controlled electronic switching circuit in
`touch plate 12, this body capacitance is coupled to a
`which the body capacitance of the person actuating the
`series voltage dividing circuit coupled to the AC supply
`device is coupled in a voltage dividing circuit employed
`and including at least one other capacitor 47. The touch
`to provide a logic output signal for controlling a DC
`plate or terminal 12 is coupled to one terminalofa first
`trigger level applied to a Triac or otherbilateral solid-
`resistor 44 serially coupled to a second resistor 46 hav-
`state switch coupled between the line voltage source
`ing its. terminal remote from resistor 44 coupled to the
`and a load to be controlled. In the preferred embodi-
`base terminal 52 of a solid-state switch 50 comprising a
`ment of the invention, the body capacitance is coupled
`PNPtransistor. Base 52 is also coupled to line supply
`in series with current limiting resistors and a second
`conductor 30 byafirst diade 45 having a cathode cou-
`capacitor with the junction coupled to a solid-state
`pled to the conductor 30 and an anode coupled to base
`switch for providing a control ouput signal to a logic
`terminal 52. Capacitor 47 is also coupled between base
`circuit which responds thereto to provide a direct cur-
`terminal 52 and line 30 and is coupled effectively in
`rent control signal. In the preferred embodiment of the
`series with body capacitor 42 to form a capacitive volt- °
`invention also, the logic circuit includes a D-flip/flop
`age divider including series resistors 44 and 46 between
`circuit having its output coupled to the input gate termi-
`coductor 30 and ground which also correspondsto the
`nal of a Triac for providing a direct current control
`ground conductor 40 of the building’s supply line. The
`signal during each half-cycle of each cycle of the line
`emitter terminal 41 oftransistor 50 is coupled directly to
`voltage supplied to the Triac and load.
`conductor 30 while the collector terminal 53 is coupled
`Such a circuit provides improvedreliability of opera-
`to a capacitor 55 coupled in parallel with resistor 56 and
`tion since it does not rely upon induced voltagefor its
`having their terminals remote from collector terminal
`operation. Further, by utilizing a direct current control
`53 coupled to a negative DC supply conductor 60
`signal for the solid-state switch, the Triac switch is
`which is coupled to the neutral or ground conductor 40
`rendered conductive near the beginning of each half-
`through a resistor 62 and series coupled rectifier diode
`64 as shwon in FIG.1.
`cycle of operation and remains conductive during each
`half-cycle of each cycle of operation. Thus, through a
`Transistor 50 is biased in a normally nonconductive
`DC gate signal,
`inductive loads such as fluorescent
`state by a resistor 54 coupled between base terminal 52
`lights, motors, etc., may be controlled. These and other
`and emitter terminal 51 such that in the absence of body
`objects, features and advantages of the present inven-
`capacitace 42, transistor 50 will be nonconductive and
`tion can best be understood by reference to the folow-
`capacitor 55 will be discharged by bleeder resistor 56
`
`~5
`
`20
`
`30
`
`35
`
`60
`
`3
`
`

`

`OPERATION
`
`4,731,548
`
`—9
`
`— a
`
`4
`tively, of circuit 9 are intercoupled, while terminal 14
`(Vpp) of circuit 90 is coupled to line 30 as seen in the
`FIGURE.
`
`3
`such that the outputsignal present at collector terminal
`53of transistor 50 will be a logic zero or low level. This
`input circuit thus will provide a first control output
`signal which is at a logic low level when plate 12 is not
`touched anda second level or logic high level when the
`plate 12 is touched. The touching of plate completes an
`Having described the componentsand their intercon-
`AC voltage divider between line 30 and 40 including
`nection to form the circuit of the present invention, a
`series capacitors 47 and 42 with resistors 44 and 46
`description of a cycle of operation is now presented. As
`serially. Thus with the presence of capacitor 42, the AC
`noted above, when poweris initially applied to the
`voltageat the base 52 oftransistor 50 during thepositive
`circuit and there is no body capacitance 42 in the cir-
`half-cycles of the line voltage will be decreased to for-
`cuit, the biasing of the SET terminal of D-flip/flop 90
`wardly bias the emitter-to-base junction thereby render-
`will maintain the Q output high and therefore the Triac
`ing transistor ‘50 conductive. The collector current thus
`20 in the nonconductive state. When touch plate 12 is
`charges capacitor 55 to provide a positive voltage level
`touched thereby adding capacitance 42, as noted earlier,
`or logic “1” output signal for application to circuit 80.
`transistor 50 is rendered conductive during the positive
`‘ Resistors 44 and 46 should eachhavea resistanceofat
`half-cycles of each cycle of the AC supply line voltage,
`least 1 megohms, and in the preferred embodiment of
`thereby charging capacitor 55 and providing a positive
`the invention, each have a value of 4.7 megohms which
`output signal indicated by waveform A in the FIGURE
`provides isolation between touch plate 12 and suppply
`at the Q output 13 of squaring circuit 80. This signal is
`line 30 so that no harmful electrical current can be
`applied to the clock input terminal 3 of D-flip/flop 90
`supplied to a person touching plate 12. Twoserially
`causing the output terminal 1 to switch to the state of
`coupled resistors are employed in the unlikely event
`terminal 5 which on initial power up was at the low
`that one resistor could short out, the second resistor
`level. Thus, when plate 12 is first touched at a time t), a
`continues to provide protection for the user of the cir-
`negative pulse indicated by waveform B in the FIG-
`cuit. Capacitor 47 was a 0.01 Mfd capacitor in the pre-
`URE will be applied to the Triac 20 rendering it con-
`ferred embodiment. Diode 45 prevents the base-to-emit-
`ductive and illuminating lamp 26 or applying power to
`ter junction oftransistor from being subjected to re-
`whatever appliance is coupled to terminals 24 and 27.
`verse breakover voltages.
`Whenthe user removes contact with touch plate 12,
`‘A 15 volt DC power supply 70 is included within
`transistor 50 is nonconductive and capacitor 55. dis-
`= circuit 10 for providing power to the logic circuits 80
`charges through resistor 56; however, the D-flip/flop
`and 90. Supply 70 includesresistor 62 and diode 64 and
`90 is latched and output 1 remains at a direct current
`---“a voltage regulator circuit including a 15 volt Zener
`low level and the Triac 20 remains conductive during
`“diode 72 coupled in parallel with a resistor 74 and ca-
`each half-cycle of each cycle of the applied line fre-
`pacitor 76. One termninal ofthis parallel combinationis
`quency voltage. The next time, however, touch plate 12
`coupled to conductor30, as shown, while the remaining
`is touched, generating a second positive pulse on input
`terminal is coupled to DC supply conductor 60 which
`terminal 9 of squaring circuit 80, a second positive pulse
`applies a negative 15 volt DC for the logic circuit now
`also indicated. by waveformAis applied to terminal 3 of
`described.
`circuit 90. The flip/flop circuit 90 responds to change
`The logic circuit coupled to transistor 50 and to the
`states and provide a positive going edge to waveform B
`“gate terminal 23 of Triac 20 comprises a two-stage com-
`indicated at time tz in the Figure, thereby turning the
`“mercially available 4013B integrated circuit having one
`Triac 20 off and extinguishing lamp 26. Thus, alternate
`half coupled as a squaring circuit 80 and the second half
`touches of plate 12 will cause flip/flop 90 to change
`coupled as a conventional D-flip/flop circuit 90. The
`states for providing the control pulse to the Triac 20.
`terminal identification numbers on circuits 80 and 90 are
`Waveform B provides a continuous DC signal as op-
`the standard commercial identification numbers of the
`posed to alternate half-cycle pulses thereby rendering
`integrated circuit.
`the Triac conductive during the entire cycle of line
`The squaring circuit 80 respondsto positive going 60
`frequency voltage applied between conductors 30 and
`Hz clock pulses from conductor 40 through current
`40 which efficiently provides power to lamp 26. A
`limiting resistor 82 which pulsesare applied to the clock
`suitable adjustable time delay and reset circuit can be
`input terminal 11 of the circuit. The squaring circuit
`coupled between the squaring circuit 80 and triac 20 to
`also receives the control signal from the collector of
`provide an adjustable duty cycle of power to load 26.
`transistor 50 present across resistor 56 which is applied
`The circuit of the present invention therefore pro-
`to input terminal 9 which is the D inputof the circuit.
`vides a relatively inexpensive and efficient circuit in
`Circuit 80 responds to a positive signal on input 11
`which operation is improved by providing an AC volt-
`when body capacity 42 is present to provide a positive
`age dividing network including the body capacitance as
`pulse at the Q output terminal 13. This signal is shown
`a controlled element and a DC control signal for the
`by waveform A in the FIG.and has a pulse width corre-
`gate of a bidirectional switch such as a Triac. The sys-
`sponding generally to the length of time plate 12 is
`tem utilizes a minimum of components with safety fea-
`touched. Pulse A is applied to input terminal 3 ofcircuit
`tures for protecting the user. It will become apparent to
`those skilled in the art that various modifications to the
`90 which has its SET terminal 6 coupled to conductor
`60 through resistor 92 and to conductor 30 through
`preferred embodiment of the invention can be made
`capacitor 94 such that wheninitial poweris turned on,
`without departing from the spirit or scope thereof as
`this voltage divider holds the SET terminal in a high
`defined by the appended claims.
`The embodiments of the invention in which an exclu-
`state assuring that the Q output at terminal 1 remains
`high and therefore the Triac 20 which is coupled to the
`sive property or privilege is claimed are defined as
`follows:
`Q output terminal 1 of circuit 90 through resistor 96
`remains nonconductive when poweris initially applied
`1. A touch controlled electric switching circuit com-
`prising:
`to the circuit. The D and Q terminals 5 and 2, respec-
`
`25
`
`40
`
`60
`
`4
`
`

`

`4,731,548
`
`5
`
`15
`
`6
`5
`7. The circuit as defined in claim 6 wherein said logic
`a source of power for the actuation of a load to be
`circuit comprises a squaring circuit serially coupled to a
`selectively. coupled to said source of power;
`D-flip/flop circuit.
`a controllable means for selectively coupling said
`8. A touch contrailed electric switching circuit com-
`source to a load; and
`prising:
`a control circuit including a series voltage divider
`a source of alternating current power for the actua-
`inputcircuit including at least one capacitor having
`tion of a load to be selectively coupled to said
`a first terminal connected to said source of power
`source;
`and an input touch terminal for coupling a person’s
`a first solid-state switch for selectively coupling a
`body capacitance in series with said at least one
`load to said source and having a control input ter-
`capacitor such that the voltage across said one
`minal for receiving control signals; and
`capacitor produced by said source of power is
`a control circuit including a touch plate responsive to
`changed whensaid input touch terminal is touched
`the touch of an individual to provide a direct cur-
`and said control circuit provides a control output
`rent controi output signal applied to said control
`signal in response to the touching of said touch
`input terminal such that said first switch is ren-
`terminal whichsignal is applied to said controllable
`dered conductive during each half-cycle of each
`means for selectively coupling said source of
`cycle of applied alternating current voltage,
`powerto said load.
`wherein said control circuit includes a series volt-
`2. The circuit as defined in claim 1 wherein said
`age divider input circuit including said touch plate
`20
`source of power is an alternating current source and
`and at least one capacitor having a terminal remote
`wherein said controllable means comprisesafirst solid-
`from said touch plate connected to said source of
`state switch.
`alternating current power for coupling a person’s
`3. The circuit as defined in claim 2 wherein said input
`body capacitance in series with said at least one
`circuit is coupled to said source of power and includes
`capacitor and said source of alternating current
`resistance means coupled in series between said touch
`powersuch that said control circuit respondsto the
`terminal and said at least one capacitor.
`change in voltage across said one capacitor to se-
`4. The circuit as defined in claim 3 wherein said resis-
`lectively provide said direct current control signal.
`tance means comprises a pair of serially coupled resis-
`9, The circuit as defined in claim 8 wherein said input
`tors each having a resistance of at least 1 megaohm.
`circuit is coupled to said source of power and includes
`§. A touch controlled electric switching circuit com-
`resistance means coupled in series between said touch
`prising:
`plate and said at least one capacitor.
`10. The circuit as defined in claim 9 wherein said
`a source of power for the actuation of a load to be
`resistance means comprises a pair of serially coupled
`selectively coupled to said source of power;
`resistors each having a resistance of at least 1 megohm.
`a controllable means for selectively coupling said
`source to a load; and
`11. A touch controlled electronic switching circuit
`comprising:
`a control circuit including a series voltage divider
`a source of alternating current power for the actua-
`input circuit including at least one capacitor and an
`tion of a load to be selectively coupled to said
`input touch terminal for coupling a person’s body
`source;
`capacitance in series with said at least one capaci-
`a first solid-state switch for selectively coupling a
`tor such that the voltage between said one capaci-
`tor and said touch terminal
`is
`reduced when
`load to said source and having a control inputter-
`minal for receiving control signals; and
`touched and said control circuit provides a control
`a control circuit including a touch plate responsive to
`output signal in response to the touching of said
`the touch of an individual to provide a direct cur-
`touch terminal which signal is applied to said con-
`rent control output signal applied to said control
`trollable means for selectively coupling said source:
`input terminal such that said first switch is ren-
`of power to said load, wherein said source of
`dered conductive during each half-cycle of each
`poweris an alternating current source and wherein
`cycle of applied alternating current voltage,
`said controllable means comprisesa first solid-state
`wherein said control circuit includes a series volt-
`switch, wherein said input circuit is coupled to said
`age divider input circuit including at least one ca-
`source of power and includes resistance means
`pacitor and said touch plate is coupled to said at
`coupled in series between said touch terminal and
`least one capacitor for coupling a person’s body
`said at least one capacitor, wherein said resistance
`capacitance in series with said at least one capaci-
`means comprises a pair of serially coupledresistors
`tor such that said control circuit selectively pro-
`each havinga resistance ofat least 1 megaohm and,
`vides said direct current control signal, said source
`wherein the junction of said at least one capacitor
`of powerand includesresistance means coupled in
`and said resistance means is coupled to a control
`series between said touch plate and said at least one
`terminal of a second solid-state switch coupled to
`capacitor, wherein said resistance means comprises
`said powersource and responsive to the change in
`a pair of serially coupled resistors each having a
`capacitance and resulting voltage change at said
`resistance of at least 1 megaohm and, wherein the
`junction to provide a controlling signal.
`junction of said at least one capacitor and said
`6. Thecircuit as defined in claim 5 wherein said con-
`resistance means is coupled to a contro! terminal of
`trol circuit further includes a logic circuit having an
`a second solid-state switch coupled to said power
`input terminal coupled to said second solid-state switch
`source and responsive to the change in capacitance
`and output terminal coupled. to said first solid-state
`and resulting voltage change at said junction to
`switch, said logic circuit latching in response to succes-
`provide a controlling signal.
`12. The circuit as defined in claim 11 wherein said
`sive controlling signals for providing said control out-
`putsignal.
`control circuit further includes a logic circuit having an
`
`35
`
`25
`
`45
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`twa0
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`5
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`

`

`7
`input terminal coupled to said secondsolid-state switch
`and ouput
`terminal coupled to said first solid-state
`switch, said logic circuit latching in response to succes-
`sive controlling signals for providing said control out-
`put signal.
`13. The circuit as defined in claim 12 wherein said
`logic circuit comprises a squaring circuit serially cou-
`pled to a D-flip/flop circuit.
`14. A touch controlled electrical switching circuit for
`controlling power applied to a load, said circuit com-
`prising:
`a solid-state switch and means for coupling said
`switch between a load to be controlled and a sup-
`ply of electrical power, said switch having a con-
`trol input.terminal; and
`a control circuit including an input circuit and a logic
`circuit for receiving tactile command information
`from an operator and for providing a control out-
`put signal applied to said control input terminal of
`said solid-state switch, wherein said input circuit
`includes a touch terminal coupled to at least one
`capacitor having a terminal remote from said touch
`terminal coupled to the supply of powerto define a
`voltage divider circuit with a person’s body capaci-
`tance, said input circuit further including resistance
`means coupled in series with said touch terminal
`and said capacitor for limiting currentto said touch
`terminal and voltage level responsive means re-
`sponsive to said voltage divider circuit for causing
`said logic circuit to changethe state of said control
`output signal.
`15. A touch controlledelectrical switching circuit for
`controlling power applied to a load, said circuit com-
`prising:
`a solid-state switch and means for coupling said
`switch between a load to be controlled and a supply of
`
`8
`electrical power, said switch having a control input
`terminal; and
`a control circuit including an input circuit and a logic
`circuit for receiving tactile command information
`from an operator and for providing a control out-
`put signal applied to said control input terminal of
`said solid-state switch, wherein said input circuit
`includes a touch terminal coupled to at least one
`capacitor having a terminal remote from said touch
`terminal coupled to the supply of powerto define a
`voltage divider circuit, said input circuit further
`including resistance means coupled in series with
`said touch terminal and said capacitor for limiting
`current to said touch terminal, wherein said input
`circuit further includes a second solid-state switch
`having a control input terminal coupled to said
`touch terminal and to the supply of operating
`powerand responsive to the touching ofsaid touch
`terminal for changingstate.
`16. The circuit as defined in claim 15 wherein said
`’ control circuit further includes a logic circuit including
`a latching circuit having an output terminal coupled to
`said control input terminal ofsaid first namedsolid-state
`switch.
`17. The circuit as defined in claim 16 wherein said
`resistance means comprises a, pair of serially coupled
`resistors each having a resistance of at least 1 megohm.
`18. The circuit as defined in claim 17 wherein said
`logic circuit includes a squaring circuit coupled to said
`latching circuit and said latching circuit comprises a
`D-flip/flop circuit.
`19. The electrical circuit as defined in claim 18
`wherein said first named solid-state switch comprises a
`Triac.
`*
`*
`*
`*
`*
`
`4,731,548
`
`15
`
`20
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`35
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`45
`
`50
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`55
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`65
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`6
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`

`

`
`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`
`4,731,548
`:
`PATENTNO.
`March 15, 1988
`:
`DATED
`Ronald D, Ingraham
`:
`INVENTOR(S)
`It is certified that error appears in the above-identified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`line 56:
`Column 2,
`“terminal 41" should be --terminal 51--
`Column 2,
`line 64:
`“shwon" should be -~shown——
`Column 4,
`line 56:
`"eontrolled™ should be --controlling——
`Column 6, claim 8, line 4:
`"electric" should be —-electronic-—
`Column 6, claim 11,
`line 55:
`After "control signal” insert --wherein said input circuit
`is coupled to-—
`
`Commissioner of Patents and Trademarks
`
`Signed and Sealed this
`
`Twenty-fifth Day of October,
`
`Attest:
`
`Attesting Officer
`
`DONALD J. QUIGG
`
`7
`
`