1. Field of the Invention
The present Invention concerns an apparatus for the electrochemical treatment of a human body or of an animal body, in particular for the destruction of tumor tissues with one or several electrodes for introduction into the body to be treated, wherein the electrodes are disposed at a distance relative to each other.
2. Brief Description of the Background of the Invention Including Prior Art
Various methods and apparatuses for the destruction of tumor tissues have become known. For example according to U.S. Pat. No. 4,565,200 high frequency technologies are employed in order to coagulate tissues and/or to separate tissues. Preferably a frequency region from 300 kHz to 2 MHz is employed here. This pre-known bipolar electrode arrangement comprises two parallel disposed needle electrodes, wherein the needle electrodes are being stung into the tissue, and whereby the tissue disposed between the electrodes is heated based on the current flow and therewith coagulated.
The German printed Gebrauchsmuster DE 20003952 U1 describes a sonde, which is connected with a connector to a generator by way of a plug connection. The sonde comprises a flexible part and stiff parts successively following to the flexible part, wherein the electrodes are disposed at the end of the stiff parts. The overall construction provides only limited conveniences to the practitioner physician.
The European patent document EP 0871405 B1 teaches a bipolar high frequency surgical instrument. An electrically not conducting spacer or holder is provided, wherein the distance holder is brought in between the electrodes, that is between the claws of the tongue during a cutting of tissue. At least one channel is furnished, which serves as a flushing and/or suction channel.
Werner Seifermann in the journal Onkologie, issue 9, year 2004, p. 33 describes bio Electro tumor therapy. A self focusing current is driven through the tumor by way of an exact electrode arrangement. The article alleges that the electrical resistance of the tumor is 10 times lower as compared to the healthy tissue and consequently the current focuses in the tumor and polarizes the tumor. HCl is generated by this electrolysis and damages the cell membranes of the tumor tissue.
A high frequency therapy device is also described in the European patent 0714635 B1, wherein frequencies from 300 kHz to 1 MHz are employed, wherein temperatures in the region of from 60 to 100 degrees centigrade are generated in the region of the electrode tip for coagulation or, respectively, necrotization of the tissues.
These so-called thermal treatment methods are associated with the disadvantage that the complete body of the patient is subjected to this alternating voltage.
1. Purposes of the Invention
Therefore, it is an object of the present Invention to create an instrument and a method for the destruction of tumor tissues, wherein the electrical load of the patient is small and wherein no thermal load occurs.
It is another object of the invention to provide a reliable instrument for necrotization of tumor tissue based on electrolyzing.
These and other objects and advantages of the present invention will become evident from the description which follows.
2. Brief Description of the Invention
The present invention provides
This object is achieved starting from an arrangement for electrochemical treatment of the human body or of an animal body, in particular for the destruction of tumor tissues with one or several electrodes for insertion into the body to be treated, and with the instrument of the present invention comprising a generator (1) for generating a DC voltage, connection lines (2,3,3′) connected to the generator (1), at least one trocar sleeve′ (7,7) attached to one of the connection lines, at least one trocar thorn (12) to be inserted into the trocar sleeve, and at least one electrode (5,5′) to be connected to one of the connection lines and to be inserted into the trocar sleeve.
It is possible to destroy liver tumors electrochemically with the aid of the Invention instrument and the therewith applicable method while employing the today wide spread minimally invasive operation method. A DC current generated by a generator is led through special platinum electrodes into the tumor of the respective organ according to this method. A precise placement of these electrodes can be controlled by way of x-ray measurements or by ultrasound measurements.
The DC current, which flows between two or several platinum electrodes, leads to a destruction of tissue by way of electrolysis. A substantial pH value shifting occurs in the issue based on the ionic migration. A dissociation occurs. An acid pH value (acidosis) and chlorine gas is formed at the anode. An alkaline pH value (alkalosis) is generated at the cathode and hydrogen gas is formed. The pH values are disposed outside of the physiological region and are damaging to tissue. The DC current also leads to a change of the membrane potentials by changing the electrolyte environment around the cell and in the cell. Important physiological functions as for example the potassium-sodium-pump are disturbed by the change of the membrane potentials, that is the change of a basic environment to an acid environment effects the formation of necrosis. Various salts disassociate into cations and anions in an electrical field such that the homoeostasis and biological equilibrium of the cell is lifted. The tumor tissue is devitalized.
The electrical devitalization is no usual electrical injury. An expulsion of the electricly induced necrosis takes place only after some time. The losses of substance correspond to the original spread of the tumor tissue by size, that is depending on the size of the tumor different multitudes of electrodes are required.
This non-thermal method improves the compatibility of the treatment generally based on the lack of temperature variations and permits the performance of the treatment under local anaesthesis. A further advantage is furnished in that the electrical current does not flow through the body of the patient. The operation and action of the DC current takes place only between the electrodes.
It is a further advantage of this method that the transcutaneous minimally invasive treatment of non-resectable tumor is possible with the cyto reduction.
An application of the electrodes occurs mostly percutaneously under local anaesthesis. A fitting trocar is led up to the tumor for this purpose. The electrode is then positioned in the trocar. The positioning of the electrodes should be continuously monitored through for example ultrasound instruments.
Bipolar electrodes are employed at sizes of tumors from 10 to 20 mm diameter. The bipolar electrode is led into the middle of the tumor with the aid of a trocar, such that the active electrode part is disposed in the middle third of the metastases.
Mono polar electrodes are employed with the tumor sizes from 10 to 50 mm. Mono polar electrodes are inserted into the tumor with the aid of a trocar at the boundary of the medium third of the tumor. The active part is adjusted (one-third of the diameter of the tumor). The distance between the electrodes should amount to at least 15 mm. The electrodes should always be inserted into the tumor with the aid of picture furnishing ultrasound methods (for example C-arc). Since the tumor tissue exhibits a much lesser electrical internal resistance as compared to healthy tissue, healthy tissue is not damage upon careful adjustment of the individual values. Healthy tissue exhibits and about 10 times higher electrical resistance as compared to tumor tissue.
The novel features which are considered as characteristic for the invention are set forth in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
The Invention is in the following by way of example and by way of drawings described; there is shown:
a: the arrangement trocar sleeve, adjustment element, and trocar thorn;
b: the arrangement trocar sleeve, adjustment element, and electrode;
The perspective view shown in
A complete instrument is illustrated in
The parameters required for the treatment can be separately adjusted for the individual connection bushings. Depending on the case of application—as can be recognized from
The length of the electrodes depends on the field of application. Depending on the location of the tumor in the body, the corresponding trocar sleeve (7) and coordinated trocar thorn (12) and needle electrode (5) are selected of an appropriate length. The length of the free electrode part depends on the size or, respectively, the thickness of the tumor.
The hook shaped angle of the needle electrode serves as a stop and for a safe contacting with the plug element. The needle electrode is inserted into the trocar sleeve through the adjustment element (6) and the handle part (17).
One trocar thorn (12) is inserted in a trocar sleeve (7) for safe positioning of the electrodes (5,5′) in the tumor and the trocar thorn (12) is screwed onto the thread (18) of the handle part (17) by way of a thread formed into the handle. The tip of the trocar thorn (12) is ground very sharp such that the units trocar sleeve/trocar thorn can be shifted relatively easy through the skin. The surgeon can place the tip of the trocar thorn very precisely in the tumor under control by ultrasound or x-rays. If the predetermined location has been reached then the surgeon pulls the trocar thorn (12) out of the trocar sleeve (7) and then shifts the electrode (5) into the trocar sleeve (7). Since the electrode (5) and the trocar thorn (12) exhibit the same length, the electrical connection to the generator (1) can be produced after the fixation of the electrode. It is sufficient to employ two electrodes in case of smaller tumors. If however a larger tumor is concerned, then four or more electrodes have to be placed in the tumor. The instrument cable (3,3′) is furnished with several plugs (4,4′) corresponding to the number of required electrodes. If the polarity has been fixed for the plugs (4,4′), then the plugs (4,4′) are designated respectively with “+” and “−”. Of course, also a color designation or marking with numbers and/or letters is possible.
Preferably the cables are braided copper cables. The connections provided are plug connections. It is not important at which end the plugs and the sockets are disposed. Preferably sockets are provided on the generator side and plugs are provided at the side of the electrodes.
The trocar sleeve (7,7′) is also shown in
A special securing of the trocar sleeve (5) is not required. The physician observes the markings at the trocar sleeve (7) and holds the trocar sleeve (7) with one hand by using the other hand for changing the electrode (5) or the trocar thorn (12).
The alignment of the electrodes by the physician is performed under ultrasonic control or under MRT-or CT-monitoring. If desired the physician can pre-drill a hole with the biopsy set and then can employ the trocar sleeve or isolating sleeve.
The trocar sleeve (7) is preferably a straight sleeve. The trocar sleeve can also be bent. Advancing a trocar sleeve (7) would require that the trocar thorn (12) and also the needle electrode (5) are formed from a flexible material. Wire platinum is a relatively soft metal, nevertheless a straight electrode can be handled easier as compared to a bent electrode.
The electrode (5) is made out of platinum or at least in the region, which comes into contact with the tumor tissue, is made of platinum. The trocar thorn (12) comprises stainless-steel or a titanium alloy or titanium and the trocar sleeve (7) comprises a plastic which can be cleaned in an autoclave such as for example poly tetra fluoro ethylene or PEEK MT. The trocar sleeve 7 is preferably made out of an electricly nonconducting material such as for example poly tetra fluoro ethylene or PEEK MT. Liquids can be fed into the tumor through the trocar sleeve (7).
The adjustment element serves for adjusting the part of the needle electrode protruding from the trocar sleeve. The adjustment element can also be designated as a spacer piece. If for example the needle electrode is to protrude by 10 mm from the front and of the trocar sleeve, then the 10 mm adjustment element is inserted; if the electrode is to protrude by 30 mm, then the 30 mm element is employed. The accompanying sketch clarifies that the trocar sleeve or isolating sleeve exhibits a certain useful length and that the electrode protrudes by a certain measure from the trocar sleeve or from the isolating sleeve. The number of mm by which the electrode protrudes from the trocar sleeve is shown by the so-called adjustment element and is in this case 30 mm. Preferably three different electrode sets are employed, that is a set 50, a set 100, and a set 150, which means that the respective useful length of the trocar sleeve or of the isolating sleeve amounts to 50 mm, 100 mm or 150 mm. The physician has many possibilities of combination when employing different length electrodes, depending on the shape of the tumor and depending on where the tumor is disposed in the body of the patient. Advantageously the sets are distinguished by different surface coloration.
It can be recognized in
Two different applications are shown in
The single pole electrodes (25′, 25″) are inserted into the tumor (30′) of the liver (33′) at the border of the medium third (32′) with the aid of trocar sleeves in the mono polar electrode arrangement shown in
There can be different requirements as to how complete the tumor tissue has to be subjected to necrosis. In case the tumor is to be destroyed completely, it may be advisable to place the first electrode outside of the tumor, but near the tumor into healthy tissue.
The functional unit 15 of
A seven segment display 105 is provided for each of the three channels. The display indicates the value of the selected parameter during setup and the displays the recommended treatment time t during treatment.
The channel 1 function panel is shown at 106. The operating parameters for channel 1 are set out by using the arrow keys 112. The numerical display increments when the ‘arrow up’ key is pressed and decrements when the ‘arrow down’ key is pressed. The value indicated on the display 105 corresponds to the parameter data selected with the keys 109, 110, 111, or 115.
The channel 2 function panel is shown at 107. To operating parameters for channel 2 are set out by using the arrow keys 112. The numerical display increments when the ‘arrow up’ key is pressed and decrements when the ‘arrow down’ key is pressed. The value indicated on the display 105 corresponds to the parameter data selected with the keys 109, 110, 111, or 115.
The channel 3 function panel is shown at 108. To operating parameters for channel 1 are set out by using the arrow keys 112. The numerical display increments when the ‘arrow up’ key is pressed and decrements when the ‘arrow down’ key is pressed. The value indicated on the display 105 corresponds to the parameter data selected with the keys 109, 110, 111, or 115.
The current parameter key ‘mA’ 109 is used to set up the treatment current in mA from about 10 to 120 mA. This key 109 is used to monitor the effective current and the set current during treatment.
The time parameter key ‘t’ 110 is used to set out the entire treatment duration in min. with a maximum of 240 min.. The key 110 is used to monitor the set time during treatment. The recommended time t, the residual time, is continuously displayed during treatment. This residual treatment time cannot be used for time measurement purposes, since the residual time depends on the effective treatment current and the residual charge according to the equation t=Q/I, wherein t is the residual treatment time, Q. is the residual charge, and I is the up-to-date current.
The charge parameter key ‘C’ 111 is used to set up the charge in Coulomb with a maximum of 999 Coulomb. The charge parameter key 111 is used to monitor the residual charge current and to set the charge during treatment.
The up/down arrow key 112 is used to increase or decrease the value of the selected parameter during setup.
The start/stop key 113 is used to start or stop or, respectively, interrupt or continue the treatment.
The enter key 114 is used to select the channel to confirm the set value or to return to the setup mode of the apparatus.
The voltage parameter key 115 is used to set the voltage in volt.
The channel 1 indicator 116 is used to indicate if the channel 1 is defective. The defective channel 1 is also indicated by the current error indicator 120 or probe short circuit indicator 121. A defective channel 1 can also be indicated with the designation ‘Err’ on the display.
The channel 2 indicator 117 is used to indicate if the channel 2 is defective. The defective channel 2 is also indicated by the current error indicator 120 or probe short circuit indicator 121. A defective channel 2 can also be indicated with the designation ‘Err’ on the display.
The channel 3 indicator 118 is used to indicate if the channel 3 is defective. The defective channel 3 is also indicated by the current error indicator 120 or probe short circuit indicator 121. A defective channel 3 can also be indicated with the designation ‘Err’ on the display.
The device error indicator 119 indicates a problem with the device. The device error can be detected during the unit itself test or during operation. In such a case the unit is no longer operable.
The current error indicator 120 indicates a current error if the set current and the effective current, that is the treatment current, differ greatly. The current error indicator 120 indicates a current error with an acoustic and an optical (current error LED) warning if the set current and the effective current (treatment current) differ greatly. The optical warning (flashing indicator) continues as long as the error prevails, while the acoustic warning first sounds permanently and then intermittently. The warning signal remains until the current error has been rectified. When this error is indicated the effective current should be checked as soon as possible. The reason for this deviation can be a high tissue impedance, an incorrect probe placement, a connecting cable interruption, or a defective electrode. When this error occurs, the charge is correctly captured and the time adapted (prolonged or shortened).
The probe short circuit indicator 121 indicates if the probe is shorted for some reason. The indicator flashes if the impedance between the electrodes is very low and the electrodes are short circuited during operation. Then the unit should be checked and the electrodes should be checked. With this error there's the risk that the therapy current does not flow through the tumor but through the probes or within the generator unit. This can indicate an application error, a short circuit event, an electrically conductive path to connect both electrodes, or a defective electrode or a defective electrode cable.
The direct current generator of the Invention device can deliver a settable treatment current of from 10 mA to about 120 mA. The output voltage of the generator can be limited between 25 volts and 5 volts. Preferably a treatment current of from 60 mA to 80 mA is set. Also higher currents for example up to 300 mA are conceivable. The generator allows to set all values of voltage and current and their level of the voltage and current depends on a number of parameters. The proper settings can be found based on the experience of the physician.
The volume of the gases generated by the current at the electrodes 5 depend on the current density. A fixed value is not available since the parameters to be considered can be substantially different.
A type label 123 is placed on the generator apparatus giving the ratings, the serial number, the device type, and the fuse rating.
A mains socket 124 is furnished to provide power from the power grid. A power cord is employed to connect the apparatus to a wall socket. The mains socket 124 includes a fuse holder accommodating to main fuses of the device.
An equipotential bonding terminal 125 is also furnished on the rear side of the apparatus the terminal for the equipotential bonding line between the radio frequency device and the operating room's equipotential bonding bar. A yellow green equipotential bonding line is used to make the connection.
An activation light emitting diode 126 is permanently lit when treatment with the respective channel is in progress, when values were set and treatment has not yet been started, or when the user has interrupted the current treatment.
The accompanying block circuit diagram of
A second output of the digital to analog and analog to digital converter 305 is connected to an input of a limit voltage detector 302 and to an input of an output voltage regulator 303.
A specific voltage UB of the direct current generator 203 is fed to an input of the output voltage regulator 303, to an input of the limit voltage detector 302, and to an input of the no-load detector 301 as shown in
An output of the automatic voltage control circuit 201 is fed to an input of the regulator 321 of the direct current generator 203 according to
The central processing unit 205 is connected to an I/O port and level converter 325 and to an analog to digital and digital to analog converter 327. The I/O port and level converter 325 is connected to an input of a down counter 355, to a frequency divider 353, to a zero detector 329, and to an input of an output and test relay circuit 331. The I/O port and level converter 325 is connected to the over current detector 333. A
The analog to digital and digital to analog converter 327 has an output connected to an input of the automatic control 321. The I/O port and level converter 325 is further connected to the oscillator 323, to zero detector 329, to an output and test relay 331, and to an over current detector 333. A secondary current to voltage converter 335 has an output connected to the over current detector 333 and a second output connected to the regulator 321 and to a voltage to frequency converter 339 and to an input of the analog to digital and digital to analog converter 327. The oscillator 323 and the regulator 321 each have an output connected to an input of an amplifier 341. The amplifier 341 has an output connected to an input of an output voltage measuring circuit 343. The output voltage measuring circuit 343 has an output connected to an input of the automatic voltage controller 201 and to an input of the analog to digital and digital to analog converter 327.
A second output of the amplifier 341 is connected to an output transformer 345. The output transformer 345 has an output connected to an input of the rectifier 347. The rectifier 347 has an output connected to an input of the output and test relay circuit 331. A second output of the output transformer 345 is fed to an input of a current transformer 349. An output of the current transformer 349 fed to an input of the secondary current to voltage converter 335. The third output of the output transformer 345 is connected to an input of a primary current to voltage converter 351. An output of the primary current to voltage converter 351 is fed to an input of the analog to digital and digital to analog converter 327.
An output of the voltage to frequency converter 339 is fed to an input of the frequency divider 353. An output of the Zero detector 329 is fed to an input of the frequency divider 353. An output of the frequency divider 353 is fed to an input of a down counter 355. A first output of the down counter 355 is fed to an input of the zero detector 329. A second output of the down counter 355 is fed to an input of the analog to digital and digital to analog converter 327.
Mode of Operation
The treatment is always started or terminated or, respectively, interrupted through the start stop key 113 associated with a respective one of the three channels. The physician individually adjusts and activates each channel.
The trocar sleeve and the adjustment element are connected initially to each other by the physician.
The physician can apply the electrodes percutaneously under local anaesthesis. The fitting trocar is led up to the tumor for this purpose.
The physician selects the length of the electrodes depending on the field of application. The physician determines the location of the tumor in the body, and the corresponding trocar sleeve (7) and coordinated trocar thorn (12) and needle electrode (5) are selected of an appropriate length. The length of the free electrode part is determined by the physician based on the size or, respectively, the thickness of the tumor.
Then following the trocar thorn (12) is the slipped through the trocar sleeve (7) in order to stitch an opening into the tissue. Thereafter the trocar thorn (12) is pulled out and the needle electrode (5) is inserted into the stiched opening.
The electrode is then positioned in the trocar. The positioning of the electrodes should be continuously monitored through for example ultrasound instruments.
The physician uses the adjustment element for adjusting the part of the needle electrode protruding from the trocar sleeve. The adjustment element practically represents a spacer piece. If, for example, the needle electrode is to protrude by 10 mm from the front and of the trocar sleeve, then the 10 mm adjustment element is inserted; if the electrode is to protrude by 30 mm, then the 30 mm element is employed. The physician can combine various elements such as employing different length electrodes, depending on the shape of the tumor and depending on where the tumor is disposed in the body of the patient. The physician can distinguish the sets by different surface coloration.
A special securing of the trocar sleeve (5) is not required. The physician observes the markings at the trocar sleeve (7) and holds the trocar sleeve (7) with one hand by using the other hand for changing the electrode (5) or the trocar thorn (12).
a and 4b show that the trocar sleeve and the adjustment element are connected initially to each other. Then following the trocar thorn (12) is slipped through the trocar sleeve (7) in order to stitch an opening into the tissue. Thereafter the trocar thorn (12) is pulled out and the needle electrode (5) is inserted.
As shown in
The parameters employed have to be predetermined and estimated by the physician prior to treatment. The setting of the parameters (charge, current, time and output voltage) are depending on the tumor size, the tumor kind, the tumor consistency and the like. The generator is switched off after the preset charge volume (Q=D tumor×100) (D in cm) has been delivered. The number of the electrodes employed determines the voltage and the current.
The electrodes are preferably employed in the direction of the largest extension of the tumor if possible. In case other members and the bones cover the tumor then another way has to be employed for insertion of the electrodes.
In case the tumor is disposed deeply in the body of the patient and also is relatively large, then the Invention method can also be performed step-by-step. This means that the physician shifts in the trocar sleeve or isolating sleeve first to the extreme necessary depth and then pulls sleeve and electrode backward step-by-step.
The joining of the individual parts is shown in
The parameters required for the treatment can be separately adjusted for the individual connection bushings. Depending on the case of application—as can be recognized from
The physician aligns the electrodes under ultrasonic control or under MRT-or CT-monitoring.
The physician can pre-drill a hole with the biopsy set and then can employ the trocar sleeve 7 or isolating sleeve.
The physician can feed liquids into the tumor through the trocar sleeve 7.
The physician inserts the needle electrode into the trocar sleeve through the adjustment element (6) and the handle part (17).
Haemostasis or blood stanching is only required, in case larger vessels are injured. Haemostasis can be performed for example by coagulation with the electrode pulled out of the trocar sleeve or isolating sleeve, then applying voltage to the electrode and thereby performing an electro-coagulation. The physician determines if blood stanching is required and if appropriate performs electro-coagulation of the blood in question.
The treatment time can be freely selected. For electrolysis the current I, the charge Q, and the time t are set, and therein relationship Q=I×t holds. The maximum treatment time is 240 min. the maximum preset charge is 999 Coulomb.
The completeness of electrolysis is determined by a control with ultrasound, computer tomogram CT, or MRT immediately after the treatment and for control purposes another time a day later.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of electrolytic system configurations and tumor removal procedures differing from the types described above.
While the invention has been illustrated and described as embodied in the context of an instrument for the destruction of tumor tissues, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.
1—generator
2—connection cable
3,3′—instrument cable
4,4′—plug
5,5′—electrode
6,6′—adjustment element
7,7′—trocar sleeve
8—connection line
9—switching box
10—output cable
11—plug
12—trocar thorn
13—connection bushing
14—power switch
15—function units
16—
17—handle part
18—thread
19—outer thread
20—handle
25, 25′, 25″, 25a, 25b, 25c, 25d—electrodes
26—
27—3rd tumor third
28, 28′—current flow
29—
30,30′—tumor
31,31′—first tumor third
32, 32′—second tumor third
33,33′—liver
102—first socket channel
103—socket
104—socket
105—seven segment display
106—channel 1 function panel
107—channel 2 function panel
108—channel 3 function panel
109—current parameter key ‘mA’
110—time parameter key ‘t’
111—charge parameter key ‘C’
112—up/down arrow key
113—start stop key
114—enter key
115—voltage parameter key
116—channel 1 indicator
117—channel 2 indicator
118—channel 3 indicator
119—device error indicator
120—current error indicator
121—probe short circuit indicator
122—sound volume controller
123—model and parameter label
124—power connection
125—grounding receptacle
201—automatic voltage control
203—direct current generator
205—central processing unit
207—CPU interface control circuit
209—automatic controller
210
211—oscillator and final stage
212
213—output transformer and output stage
214
215—charge control
301—no-load detector
302—limit voltage detector
303—output voltage regulator
304—cut-out circuit
305—digital to analog and analog to digital converter
321—regulator
331—oscillator
325—IO port and level converter
327—an analog to digital and digital to analog converter
328—zero detector
331—output and test relay circuit
333—over current detector
335—secondary current to voltage converter
339—voltage to frequency converter
341—amplifier
343—output voltage measuring circuit
345—output transformer
347—rectifier
349—current transformer
351—primary current to voltage converter
353—frequency divider
355—down counter
Number | Date | Country | Kind |
---|---|---|---|
10 2004 055 866.3 | Nov 2004 | DE | national |