Power source device for an electric surgical knife

Abstract

Power source device for an electric surgical knife for use with an endoscope comprising, means for supplying a high frequency signal to an electric surgical knife, a selector for determining whether or not the high frequency signal is attenuated before it is supplied to the knife, a level detecting circuit for detecting the voltage level of the high frequency signal which is attenuated and supplied to the treatment electrode of the knife, a level difference detecting circuit for detecting different voltages between the high frequency signal supplied to the treatment electrode and that supplied to the fixed electrode of the knife, and means for determining whether the conductive state of the knife is normal or abnormal using output signals from the level detecting circuit and level difference detecting circuit.

Description

BACKGROUND OF THE INVENTION

This invention relates to an electrosurgical knife device which is introduced into the abdominal cavity of a human body through an endoscope and more particularly to a power source for an electrosurgical knife capable of preventing patient from getting burnt in any other part of his body than a diseased part due to concentrated current.

An electrosurgical knife is known which comprises an active electrode which is shaped like a needle or a blade and has a very small contact area and a fixed electrode which is shaped like a plate and has a large contact area, wherein a high frequency signal is conducted between the active (or treatment) electrode and the fixed electrode through a human body. The high frequency current which is concentrated aroung the end of the active electrode whose contact area is very small causes Joule heat to be generated; this Joule heat gives rises to the explosion of a gas in the human body, thereby enabling the incision and excision of an affected part. Moreover, a signal having a little higher frequency than that of the signal for the incision and excision or a high frequency signal which is amplitude modulated by a damped low frequency signal is selectively transmitted through the human body between the active electrode and the fixed electrode, thereby thermally coagulating body proteins at an incised or excised surface to close a lymphatic vessel and a fine vessel with the resultant hemostasis or stoppage of bleeding.

Already known are a power source provided with a high frequency signal generator whose output signal is amplified in voltage and power and supplied to the electric or radio surgical knife, thereby enabling the incision and excision of a human body, and another power source provided with a high frequency generator whose output signal is amplitude modulated by a damped low frequency signal, enabling the stoppage of bleeding or hemostasis.

When the electric surgical knife is driven by any of the prior art power sources, accidents frequently occur wherein the patient gets burnt at the part which is not diseased and moreover contacts any other electrical device than the electrodes of the electric surgical knife, because the concentrated current unnecessarily flows through the patient's body when he touches said other device, while a lead line between the power source and the electric surgical knife is disconnected or a contact resistence between the patient and the electrodes of the electric surgical knife increases.

The object of this invention resides in providing a power source for an electric surgical knife introduced into the abdominal cavity of a human body through an endoscope, which detects a conductive state between the patient and the electric surgical knife or between said knife and the power source, thereby saving a patient from an accident of an electrical shock causing him to get burnt at any other part than the affected one due to concentrated current flowing through said other part when he touches a different device from the electrodes of the surgical knife.

SUMMARY OF THE INVENTION

This invention provides an electric surgical knife introduced into the cavity of a human body through an endoscope comprising a high frequency signal generator; means for supplying a high frequency signal to the radio sirgical knife; a selector device for determining whether the high frequency signal is supplied to the surgical knife in an attenuated or nonattenuated state; a level-detecting circuit for detecting the amplitude level of the high frequency current which flows through the treatment electrode of the electric surgical knife when the attenuated high frequency signal is supplied to the electric surgical knife; a level difference detecting circuit for detecting different amplitude levels between the high frequency current supplied to the treatment electrode and that supplied to the fixed electrode of the electric surgical knife when the attenuated high frequency signal is supplied to the knife; and a means for determining whether the conductive state of the knife is normal or abnormal using output signals from the level-detecting circuit and level difference-detecting circuit, whereby the high frequency signal is supplied to the knife without being attenuated when the conductive state of the knife is normal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one embodiment of this invention;

FIG. 2 is a block diagram of one modification of the embodiment shown in FIG. 1;

FIG. 3 is a block diagram of another embodiment of this invention; and

FIG. 4 is a block diagram of a further embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a selector device 78 comprises first and second gates 81 and 82, a gate signal generator 71 and a detector switch 72. There is provided a high frequency signal generator 11 whose output terminal is connected to an OR circuit 62 through the first gate 81. The output terminal of the high frequency signal generator 11 is also connected to an output adjusting circuit 12 comprising a variable resistor through a second gate 82 and the output terminal of the output adjusting signal 12 is coupled to the OR circuit 62. The output signal of the OR circuit 62 is supplied to an output transformer 31 through a series connection of a voltage amplifier 21 and a power amplifier 22. Capacitors 32 and 33 for blocking direct current are connected to the output terminal of the output transformer 31. An output transformer 31 and capacitors 32 and 33. An output signal from the output circuit 3 is supplied to an electric surgical knife 4 having an active electrode 41 and fixed electrode 42.

There is provided between the capacitor 32 and active electrode 41 a first level detector 91 for detecting the high frequency current supplied to the active electrode 41. An output signal A from the detector 91 is supplied to a third gate 83 through a series connection of a first voltage converter 99 comprising a transformer and a rectifier circuit 101. The output signal of third gate 83 is conducted to a first level detecting signal amplifier 111. A level detecting circuit 911 comprises the first dectector 91, first voltage converter 99, a first rectifier cicuit 101 and first amplifier 111. A second level detector 92 is provided between the capacitor 33 and fixed electrode 42. The second level detector 92 is used for detecting the amplitude level of the high frequency current supplied to the fixed electrode 42. An output signal B from the second level detector 92 is supplied to a fourth gate 84 through the second voltage converter 100 comprising a transformer and the second rectifier circuit 102. An output signal from the fourth gate 84 is transmitted to a differential amplifier 121 via a second level signal amplifier 112. A differential amplifier 121 is also provided with output signals from the first level signal amplifier 111. Level-detecting circuit 911, second detector, second voltage converter 100, second rectifier circuit 102, fourth gate 84, second amplifier 112 and differential amplifier 121 form a level difference-detecting circuit 912.

An output signal from the first level signal amplifier 111 is supplied to the first Schmitt circuit 131 whose input terminal also receives a standard level voltage signal from a standard level voltage setting circuit 141. Schmitt circuit 131 and standard level voltage setting circuit constitute a level comparison circuit 341. The value of the standard level voltage is determined experimentally and corresponds to an output voltage from the first level signal amplifier 111 of the first level-detecting circuit 911 upon supply of 200 mA current to the active electrode 41 of the electric surgical knife 4 in case a patient's diseased part is a stomach, and is equal to an output voltage from the first level signal amplifier 111 upon impression of a detecting signal for a conductive state on the active electrode 41 instead of the 200 mA current. An output signal from the first Schmitt circuit 131 is supplied to a first flip-flop 151. The input terminal of the first flip-flop 151 receives a signal from the gate signal generator 71 of the selector device 78 via the normally open contact of the detecting switch 72. The first flip-flop 151 is reset at the rise of an output signal from gate signal generator 71 of selector device 78 and is set at the fall of an output signal from the first Schmitt circuit 131 to send a set output signal to an AND gate 153.

An output signal from the differential amplifier 121 of the level difference-detecting circuit 912 is conducted to the second Schmitt circuit 132 and a standard level difference voltage is also supplied to the second Schmitt circuit 132 from the standard level difference voltage-setting circuit 142. The second Schmitt circuit 132 and standard level difference voltage 141 constitute a level difference comparison circuit 342. The value of the standard level difference voltage is determined experimentally and corresponds to an output voltage from the differential amplifier 121 of the level difference-detecting circuit 912 where a difference between the amount of current supplied to the active electrode 41 and that supplied to the fixed electrode 42 is maximum within an allowable range. When an output signal from the differential amplifier 121 is lower voltage than the standard level difference voltage, namely, the electric surgical knife 4 is in a normal conductive state, thereby causing an output signal to be produced at the output terminal of the Schmitt circuit 132. An output signal from the second Schmitt circuit 132 is transmitted to a second flip-flop 152. An output from the gate signal generator 71 of the selector switch 78 is also conducted to the second flip-flop 152 via the normally open contact of the detecting switch 72. The second flip-flop 152 is set at the rise of an output signal from the gate signal generator 71 of the selector device 78 and is reset at the fall of an output signal from the second Schmitt circuit 132 of the level difference comparison circuit 342, thereby causing the second flip-flop 152 now brought to a set state to produce a set signal, which in turn is supplied to the AND gate 153. The flip-flop 151 and 152 and AND gate 153 form a determination circuit 150.

An output signal from the AND gate 153 of the determination circuit 150 is supplied to a display circuit 161. The display circuit 161 indicates that the electric surgical knife 4 is in a normal state when the AND gate 153 supplies an output signal to the display circuit 161 and that the electric surgical knife 4 is in an abnormal state when the AND gate 153 does not produce any output signal.

An output signal from gate signal generator 71 is supplied to the second, third and fourth gates 82, 83 and 84 through the normally open contact of the detecting switch 72 and to the first gate 81 through the normally closed contact of the detecting switch 72. The gates 81, 82, 83 and 84 are opened when a gate control signal is impressed thereon and closed when a gate control signal is not supplied thereto. The flip-flops 151 and 152 are in a reset state when the power source is initially brought into an operative state. The embodiment shown in FIG. 1 is operated as follows.

When the electric surgical knife device is initially brought to an operative state, the first and second flip-flop 151 and 152 are in a reset state and neither of flip-flops 151 and 152 produces any set output signal, thereby preventing the AND gate 153 from producing any output signal with the result that the display device 161 shows the abnormal state of the electric surgical knife 4. As the detecting switch 72 is not operated at this stage, the normally open contact thereof is left open and the normally closed contact thereof remains closed. An output signal from gate signal generating circuit 72 is supplied only to the first gate 81 to open it, with the result that as high frequency signal is supplied to the electric surgical knife 4 via the first gate 81 without being attenuated. Since the second, third, and fourth gates 82, 83 and 84 remain closed, any high frequency current is not supplied to the output control circuit 12, nor is impressed any signal of the flip-flops 151 and 152, thereby causing the flip-flops 151 and 152 to remain reset. Under such condition the display circuit 161 shows the abnormal state of the electric surgical knife 4. However, this does not mean that the electric surgical knife 4 is abnormally rendered conducting but warns that the knife 4 is going to be operated before the conductive state of the knife device is detected or examinaed.

When the fixed electrode 42 of the electric knife 4 is attached to a patient and the normally open contact of the detecting switch 71 is closed, then the second, third and fourth gate 82, 83 and 84 are opened, the first flip-flop 151 is brought to a set state and the second flip-flop 152 to a reset state. Since, at this same time, the normally closed contact of the detecting switch 72 is opened, the first gate 81 is closed and the second gate 82 is opened. When, therefore, the active electrode 41 is made to contact a patient, high frequency current is supplied to the output control circuit 12 through the second gate 82 and has its voltage reduced by the adjusting circuit 12 to such a low level as does not affect any organ of a patient. Said high frequency current thus attenuated is supplied to the electric surgical knife 4 so as to detect its conductive state through the connecting circuit 62, voltage and power amplifiers 21 and 22. The conductive state-detecting currents which are supplied to the active electrode 41 and the fixed electrode 42 are detected in the form of detecting signals A and B respectively. The detecting signals A and B are conducted to the voltage converters 99 and 100 and rectifiers 101 and 102, from which signals of positive voltage are derived. These signals of positive voltage are amplified in the signal amplifiers 111 and 112. The voltage level of output signals from the amplifier 111 is compared with the standard voltage level which is produced by the standard voltage level setting circuit. Where the voltage level of the detecting signal A for detecting the high frequency signal supplied to the active electrode 41 with the voltage amplified by the amplifier 111 is larger than the standard voltage level preset, i.e. the conductive state of a circuit connecting together the power source, electric knife and a patient's body is normal, and the normal amount of current is supplied to the active electrode 41, then the first Schmitt circuit 131 produces an output signal and the first flip-flop 151 becomes ready to be set. This state ready to be set is actually changed to a set state when the first Schmitt circuit 131 ceases to generate an output signal and a falling output signal therefrom is supplied to the first flip-flop 151, that is, when the active electrode 41 is removed from a patient 43 or the third gate 83 is closed by again opening the previously closed normally open normally open contact of the detecting switch 72. Where the voltage level of the detecting signal A for detecting the high frequency signal supplied to the active electrode 41 with the voltage amplied by the amplifier 111 is lower than the standard voltage level preset, i.e. where a normal amount of current is not supplied to the active electrode 41 for the reason that a lead line for the electric surgical knife 4 is disconnected or a contact resistance between the electrodes 41 and 42 of the electric knife 4 and patient 43 is very large, and where the active electrode 41 does not contact the patient 43, then the first Schmitt circuit 131 does not produce any output signal and the first flip-flop 151 remains reset.

The voltage level of the detecting signal A of the high frequency signal supplied to the active electrode 41 is compared with that of the detecting signal B in the differential amplifier 121, and a difference between the voltages of the detecting signals A and B is compared in the second Schmitt circuit 132 with the standard voltage difference level preset in the standard voltage level difference setting circuit 142. Where the difference between the voltage levels of the detecting signals A and B is larger than the standard voltage level difference, that is, where the high frequency detection current does not flow through a normal circuit route for the reason that the lead line of the fixed electrode 42 of the electric surgical knife 4 is disconnected or a contact resistance between the fixed electrode 42 and patient 43 is very large, thereby causing the high frequency current to pass through any other device than the electrodes 41 and 42 of the electric surgical knife 4, then the second Schmitt circuit 132 produces an output signal so as to render the second flip-flop 152 ready to be reset. When the active electrode 41 is disconnected from the patient 43 or the third and fourth gates 83 and 84 are closed by again opening the previously closed normally open contact of the detecting switch 72, then both detecting signals A and B stop entering the differential amplifiers 121 which in turn ceases to produce any output signal, therey preventing any output signal from being delivered from the second Schmitt circuit 132, with the result that the fall of an output signal from the second Schmitt circuit renders the second flip-flop 152 ready to be reset. Where a difference between the voltage levels of the detecting signal for high frequency currents supplied to the active electrode 41 and the fixed electrode 42 is lower than the standard voltage level difference, i.e. the conductive condition of a circuit connecting together a power source, electric surgical knife and patient is normal and no leakage of current occurs through any other device than the surgical knife 4, then the second Schmitt circuit 132 does not produce any output signal and the second flip-flop 152 remains set.

When the normally closed contact of the detecting switch 72 is again closed after once opened, then the first gate 81 is opened, the second, third and fourth gates 82, 83 and 84 are closed, and the first and second Schmitt circuits 131 and 132 do not give forth any output signal and the falling portions of output signals from said Schmitt circuits 131 and 132 are supplied to the flip-flops 151 and 152 respectively, thereby causing the flip-flops 151 and 152 to be changed from a state ready to be set or reset to the one actually set or reset. When both first and second flip-flops are brought to a set state i.e. the previously opened normally closed contact of the detecting switch 72 is again closed where the detecting signal A has a voltage level higher than the standard voltage level and a difference between the voltage levels of both detecting signals A and B is lower than the standard voltage difference level, i.e. the conductive state of a circuit connecting together a patient, electric surgical knife 4 and power source is normal, then the AND gate 153 produces an output signal and the display circuit 161 indicates the normal operational condition of the surgical knife 4, thereby rendering the knife device 4 ready for operation. When the electric surgical knife 4 is in a proper operational condition and the active electrode 41 is made to contact a patient 43, and a high frequency signal generated by the high frequency generator 11 is supplied directly to a series connection of the voltage amplifier 21 and power amplifier 22, a direct current component of an output signal from the amplifier 22 is blocked by the output circuit 3 and an output signal from the output circuit 3 is supplied to the electric surgical knife 4.

When the conductive state of the electric surgical knife device is in a normal condition, the incision and exision of the affected part of the patient 43 is performed through the movement of the active electrode 41 under control of the high frequency signal.

Where at least either the flip-flop 151 or flip-flop 152 is in a reset state it also means that there occurs an abnormal state of conduction between the patient and the electric surfical knife and between the electric surgical knife and the power source for the reason that the lead line of the electric surgical knife 4 is disconnected, the electrode 41 and 42 of the electric surgical knife 4 poorly contacts the patient, or current does not run through a normal route. In such case, the AND gate 153 does not produce any output signal and the display device 161 continues to display the abnormal conductive state of the surgical knife 4, thereby reliably preventing the occurrence of an accident and protecting a patient therefrom.

If the detecting switch 72 has its normally open contact closed during a surgical operation to close the first AND gate 81 thereby preventing the high frequency current from passing therethrough and also to open the second, third and fourth gates 82, 83 and 84 thereby supplying a high frequency detecting signal to the electric surgical knife 4, then the conductive state of any circuit section is examined and whether or not there occur any abnormal conductive state of the circuit is displayed by display circuit 161 during the surgical operation, thereby saving a patient from an accident. According to the above described embodiment, the conductive states between the patient and electric surgical knife and between the electric surgical knife and power source, such as the state of contact resistance between the patient and the electric surgical knife, and the state of a lead line are detected by a relatively attenuated high frequency detecting signal, and the passage of current through any other device than the electric knife 4 when touched by the patient is detected using said relatively attenuated high frequency detecting signal to save the patient from getting burnt and also from receiving an electric shock at any other part of his body than the affected one during a surgical operation due to concentrated current passing through said unrelated part of the patient's body contacted by a different device from the electric surgical knife 4.

FIG. 2 is a block circuit diagram of one modification of an electric surgical knife device according to an application of the embodiment of FIG. 1. In addition to elements of the embodiment shown in FIG. 1, the electric surgical knife device according to the second embodiment of FIG. 2 further comprises a low frequency signal generator 51 for generating an unsynmmetrical square wave signal whose positive side is longer than the negative side thereof; a modulator 61 inserted between the high frequency signal generator 11 and the first gate 81; a clamping and differentiator circuit 52 for damping the low frequency square wave signal at the positive side and differentiating the clamped signal so as to give forth a clamped low frequency signal having a repititive frequency equal to the frequency of the low frequency square wave signal; and a selector device 53 for selectively supplying the damped low frequency signal to a modulator 61 so as to selectively amplitude modulating the high frequency signal with the damped low frequency signal, thereby the incision and excision of the affected part of a patient's body are performaed upon supply of the unmodulated high frequency signal to the surgical knife 4 and bleeding is stopped upon supply of the damped modulated high frequency signal to the electric surgical knife 4.

In the embodiment of FIG. 2, where the stoppage of bleeding or hemostasis, as well as the incision and excision of a patient's affected part, is attained, the conductive state of the surgical knife device is also examined so as to save the patient from an accident of an electric shock.

The process of switching over operation from the incision and excision to the stoppage of bleeding has already been set forth in greater detail in the U.S. Patent Application Ser. No. 424,433, filed Dec. 13, 1973 with regard to "Electrical surgical device and method of operating same."

The embodiment of FIG. 3 is different from that of FIG. 1 only in that the normally closed contact of the detecting switch 72 is omitted and the output terminal of the AND gate 153 is connected to the first gate 81 to control its condition, whereby an output signal from the gate signal generator controls the first gate 81 indirectly and the second, third and fourth gates 82, 83 and 84 directly.

While the power source is initially rendered conducting, the detecting switch 72 remains open and the second, third and fourth gates 82, 83 and 84 remain closed, thereby preventing the AND gate 153 from giving forth any output signal with the first gate 81 kept closed. Neither operational nor detecting current is supplied to the electric surgical knife 4. When the detecting switch 72 is closed, the gates 82, 83 and 84 are opened to supply detecting current to the electric surgical knife 4 for detection of its conductive state. When the conductive state is normal, the display circuit 161 indicate that the surgical knife 4 is in operational state, and the first gate 81 opens upon supply of an output signal from the AND gate 153 to the gate 81, making the electric knife device ready for operation. When the conductive state is abnormal, the AND gate 153 does not produce any output signal and the display circuit 161 continues to indicate said abnormal operational state with the first gate 81 closed, thereby preventing a high frequency operational signal from being supplied to the electric surgical knife 4.

Accordingly, the embodiment of FIG. 3 attains the same effect as that of FIG. 1 and moreover with better reliability. While the knife device is initially rendered conducting, the high frequency detecting signal is not supplied to the surgical knife 4 until the detection of the conductive state of the knife device is completed. Therefore, the embodiment of FIG. 3 also saves a patient from an electric shock.

It is also possible to obtain the above described effect by combining the embodiment of FIG. 3 with the power source for selectively carrying out the surgical operation or the stoppage of bleeding as shown in FIG. 2.

The embodiment of FIG. 4 is different from that of FIG. 3 in that the gate signal generator 71 and detecting switch 72 are omitted; the circuit for selectively carrying out the surgical operation or the hemostasis comprising a low frequency signal generator 51, a clamping and differentiating circuit 52, selector switch 53 and modulator 61 is provided; and an inverter 54 is connected between the low frequency signal generator 51 and second gate 82. A low frequency output signal from the low frequency signal generator 51 is used as a signal for controlling the selector device 78 instead of an output signal from the gate signal generator 71. A low frequency output signal from the generator 51 is an unsymmetrical square wave signal whose positive side is longer than the negative side. The low frequency square wave signal is supplied to the inverter 54 to be formed into a pulse signal which in turn is supplied to the second, third and fourth gate 82, 83 and 84 and flip-flops 151 and 152, thereby enabling the conductive state of the knife device to be detected with an interval synchronized with the frequency of the pulse signal.

The embodiment of FIG. 4 can also save the patient from an accident such as an electric shock and eliminates the necessity of providing the gate signal generator 71 and detecting switch 72, thereby simplifying the construction of the power source of the electric knife 4. Further, the detection operation is performed automatically without manually operating the detecting switch.

As described above, there is provided an electric surgical knife device for use with an endoscope, said knife device being fitted with a power source device for detecting a conductive state between a patient and the surgical knife and between said knife and power source and determining the state of contact resistance between the patient and knife, the connecting state of a lead line and the conductive route of the high frequency current, wherein, when the patient touches any other device than the electric surgical knife, current is prevented from running through the adnormal route, namely, through said other device, and the patient is saved from getting burnt by concentrated current at any other part of his body than the affected one touched by a different device from the knife and from an accident such as an electric shock.

Claims

What we claim is:

1. A power source device for supplying high frequency electrical signals on first and second output lines which are respectively adapted to be connected to active and fixed electrodes of an electrosurgical knife, comprising:

means for generating a high frequency signal;

means for supplying a high frequency signal to first and second output lines;

selector means connected to said supplying means for selectively passing said high frequency signal to said supplying means or for attenuating said high frequency signal before passing same to said supplying means;

level detecting means coupled to said supplying means for detecting the voltage level of the high frequency signal supplied to said first output line;

level difference detecting means coupled to said supplying means and to said level detecting means for detecting a difference between the voltage levels of output signals corresponding to the signals appearing on said first and second output lines;

level comparison means fro comparing the voltage level of an output signal from said level detecting means with a first fixed voltage level;

level difference comparison means for comparing the voltage level of an output signal from said level difference detecting means with a second fixed voltage level;

determining means responsive to the output signals from both said level comparison means and said level difference comparison means for determining whether or not the signals supplied to said first and second output lines are "normal" so as to render an electric knife in a normal conduction state; and

indicating means responsive to the output of said determining means for indicating whether or not said signals supplied to said first and second output lines are "normal".

2. A power source device according to claim 1 wherein said means for supplying a high frequency signal comprises means for amplifying the voltage and power of the high frequency signal; and an output circuit means for eliminating a direct current component from the amplified high frequency signal.

3. A power source according to claim 2 wherein said high frequency signal supplying means further comprises a low frequency signal generator for generating a square wave signal of low frequency; a clamping and differentiating circuit means connected to said low frequency signal generator so as to form a damped wave signal by repeating damping at a repititive frequency equal to the frequency of said low frequency signal; and means for amplitude modulating said high frequency signal with said damped low frequency signal.

4. A power source according to claim 3 wherein said selector means comprises means coupled to said low frequency signal generator for forming a pulse signal from a low frequency signal generated by said low frequency signal generator; a first gate means connected to said determining means and to the output of said modulating means so as to supply said high frequency signal without attenuation when an output signal from said determining means which indicates a normal state is delivered to said first gate means; a second gate means connected to said pulse signal forming means and to said high frequency signal generator and enabled intermittently each time a pulse signal formed by said pulse signal forming means is supplied to said second gate means; and a signal forming circuit means connected to the output terminal of said second gate means so as to cause said high frequency signal to be attenuated when said second gate means is enabled, thereby causing the attenuated high frequency signal to be supplied by said supplying means to the first and second output lines.

5. A power source according to claim 1 wherein said selector means comprises a signal generator means for generating a gate signal; a detecting switch means connected to said gate signal generator means and provided with a normally open contact and normally closed contact; a first gate means connected to said gate signal generator means so as to supply the high frequency signal to said output lines without attenuation when said first gate means is supplied with a signal from the normally closed contact of the detecting switch means; a second gate means connected to said gate signal generator means and enabled when supplied with a gate signal through the normally open contact of the detecting switch means; and an output adjusting circuit means connected to the output terminal of said second gate means and to said means for supplying so as to cause said high frequency signal to be attenuated

6. A power source according to claim 5 wherein said means for supplying a high frequency signal includes an output circuit means for eliminating a direct current component from the high frequency signal; and wherein said voltage level detecting means comprises a first detector electrically coupled to said output circuit means for detecting the amount of current supplied by said supplying means to the said first output line; a first converter and rectifier circuit means coupled to the output of the first detector; a third gate means coupled to the normally open contact of the detecting switch means and to an output of the first converter and rectifier circuit means, the operation of the third gate means being controlled by a gate signal supplied thereto through the normally open contact of the detecting switch means; and a first amplifier means coupled to the third gate means for amplifying an output signal from the third gate means.

7. A power source according to claim 6 wherein said voltage level difference detecting means comprises a second detector electrically coupled to said output circuit means for detecting the amount of current supplied by said supplying means to said second output line; a second converter and rectifier circuit means coupled to the output of the second detector; a fourth gate means coupled to the normally open contact of the detecting switch means and to the output of the second converter and rectifier circuit means, the operation of the fourth gate means being controlled by a gate signal supplied to the fourth gate means through the normally open contact of the detecting switch means; a second amplifier mena connected to the output terminal of the fourth gate; and a differential amplifier coupled to the outputs of the first and second amplifier means.

8. A power source according to claim 5 wherein said determining means comprises a first flip-flop coupled to the output of said level comparison means; a second flip-flop coupled to the output of said level difference comparison means, said first and second flip-flops being coupled to said selector means and being controlled by a gate signal from said selector means; and an AND gate means coupled to the outputs of both said first and second flip-flops; and wherein said indicating means includes a display means coupled to the output of said AND gate means.

9. A power source according to claim 1 wherein said selector means comprises a signal generator means for generating a gate signal; a detecting switch means connected to said gate signal generator means and provided with a single contact; a first gate means connected to said means for generating a high frequency signal and to an output of said determining means for supplying said high frequency signal without attenuation when an output signal from said determining means which indicates a normal condition is supplied to said first gate means; a second gate means connected to said gate signal generator means and enabled when the contact of the detecting switch means is closed; and a signal forming circuit means connected to the output terminal of said second gate means so as to cause said high frequency signal to be attenuated when said second gate means is enabled, thereby causing an attenuated high frequency signal to by supplied by said supplying means to the first and second output lines.

10. A power source device according to claim 1 wherein said level comparison means comprises a standard voltage level setting circuit means for generating said first fixed voltage level; and a first Schmitt circuit means coupled to the output of the level detecting means and to the output of the standard voltage level setting circuit means, for producing an output signal of its own when the voltage level of an output signal from the level detecting means is higher than said first fixed voltage level.

11. A power source device according to claim 1 wherein said level difference comparison means comprises a standard voltage level difference setting circuit means for generating said second fixed voltage level representing a preset standard difference; and a second Schmitt circuit means coupled to an output of the level difference detecting means and to the output of the standard voltage level difference setting circuit means, for producing an output signal of its own when the voltage level of an output signal from the level difference detecting means is lower than said second fixed voltage level.

12. A power source according to claim 1 wherein said determining means comprises a first bistable multivibrator coupled to the output of said level comparison means; a second bistable multivibrator coupled to the output of said level difference comparison means; and gating means coupling the outputs of said first and second bistable multivibrators to said indicating means.

13. An electric surgical knife device comprising:

an electric surgical knife provided with an active electrode and a fixed electrode whose contact area is larger than that of said active electrode;

a high frequency signal generator for generating a high frequency signal;

means for supplying the high frequency signal to the active and fixed electrodes of the electric surgical knife;

selector means connected to said supplying means for selectively passing said high frequency signal to said supplying means or for attenuating said high frequency signal before passing same to said supplying means;

level detecting means coupled to said supplying means for detecting the voltage level of the high frequency signal supplied to the active electrode of the knife;

level difference detecting means coupled to said supplying means and to said level detecting means for detecting a difference between the voltage levels of output signals corresponding to the signals supplied to the active electrode and to the fixed electrode;

level comparison means for comparing the voltage level of an output signal from said level detecting means with a first fixed voltage level;

level difference comparison means for comparing the voltage level of an output signal from said level difference detecting means with a second fixed voltage level;

determining means responsive to the output signals from both said level comparison means and said level difference comparison means for determining whether or not the signals supplied to said electric knife are such as to render said electric knife in a normal conductive state; and

indicating means responsive to the output of said determining means for indicating whether or not said signals supplied to said electric knife are such as to render said electric knife in a normal conductive state.