Patent Publication Number: US-10779876-B2

Title: Battery powered surgical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/658,786, entitled “BATTERY SHUT-OFF ALGORITHM IN A BATTERY POWERED DEVICE,” filed on Oct. 23, 2012, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/550,768, entitled “MEDICAL INSTRUMENT,” filed on Oct. 24, 2011, which is incorporated herein by reference in its entirety. 
     This application is related to the following commonly assigned U.S. and PCT International Patent Applications: 
     U.S. patent application Ser. No. 13/658,784, entitled “LITZ WIRE BATTERY POWERED DEVICE,” now U.S. Pat. No. 9,421,060, which is incorporated herein by reference in its entirety. 
     U.S. patent application Ser. No. 13/658,787, entitled “USER INTERFACE IN A BATTERY POWERED DEVICE,” now published as U.S. Pat. No. 9,414,880, which is incorporated herein by reference in its entirety. 
     U.S. patent application Ser. No. 13/658,790, entitled “BATTERY INITIALIZATION CLIP,” now U.S. Pat. No. 9,333,025, which is incorporated herein by reference in its entirety. 
     U.S. patent application Ser. No. 13/658,791, entitled “BATTERY DRAIN KILL FEATURE IN A BATTERY POWERED DEVICE,” now U.S. Pat. No. 9,283,027, which is incorporated herein by reference in its entirety. 
     U.S. patent application Ser. No. 13/658,792, entitled “TRIGGER LOCKOUT MECHANISM,” now U.S. Pat. No. 9,314,292, which is incorporated herein by reference in its entirety. 
     PCT International patent application Ser. No. PCT/US12/61504, entitled “MEDICAL INSTRUMENT,” concurrently filed, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to the field of medical instruments and in particular, although not exclusively, to electrosurgical instruments. The present disclosure also relates to drive circuits and methods for driving such medical instruments. Additionally, the present disclosure is directed to lockout mechanisms, user interfaces, initialization techniques, and battery power conservation circuits and methods for such medical instruments. 
     Many surgical procedures require cutting or ligating blood vessels or other internal tissue. Many surgical procedures are performed using minimally invasive techniques where a handheld instrument is used by the surgeon to perform the cutting or ligating. Conventional hand-held electrosurgical instruments are generally large and bulky and require large power supplies and control electronics that are connected to the instrument through an electrical supply line. 
     Conventional corded electrosurgical instruments are large in size, have large power supplies and control electronics, and take up a lot of space in the operating room. Corded electrosurgical instruments are particularly cumbersome and difficult to use during a surgical procedure in part due to tethering of the hand-held electrosurgical instrument to the power supply and control electronics and the potential for cord entanglement. Some of these deficiencies have been overcome by providing battery powered hand-held electrosurgical instruments in which the power and control electronics are mounted within the instrument itself, such as within the handle of the instrument, to reduce the size of the electrosurgical instrument and make such instruments easier to use during surgical procedures. 
     Electrosurgical medical instruments generally include an end effector having an electrical contact, a radio frequency (RF) generation circuit for generating an RF drive signal and to provide the RF drive signal to the at least one electrical contact where the RF generation circuit also includes a resonant circuit. The RF circuit includes circuitry to generate a cyclically varying signal, such as a square wave signal, from a direct current (DC) energy source and the resonant circuit is configured to receive the cyclically varying signal from the switching circuitry. The DC energy source is generally provided by one or more batteries that can be mounted in a handle portion of the housing of the instrument, for example. 
     The design of battery powered hand-held electrosurgical instruments requires the electronics in the power supply and RF amplifier sections to have the highest efficiency possible in order to minimize the heat rejected into the relatively small handheld package. Increased efficiency also improves the storage and operational life of the battery. Increased efficiency also minimizes the size of the required battery or extends the life of a battery of a given size. Thus, there is a need for battery powered hand-held electrosurgical instruments having higher efficiency power supply and RF amplifier sections. 
     SUMMARY 
     In one embodiment, a medical instrument includes at least one electrical contact, a battery, a radio frequency (RF) generation circuit coupled to and operated by the battery and operable to generate an RF drive signal and to provide the RF drive signal to the at least one electrical contact, a battery discharge circuit coupled to the battery, a processor coupled to the battery discharge circuit, and a memory coupled to the processor. The memory stores machine executable instructions that when executed cause the processor to monitor activation of the RF generation circuit and disable the RF generation circuit when the RF drive signal is fired a predetermined number of times. 
    
    
     
       FIGURES 
         FIG. 1  illustrates the form of an electrosurgical medical instrument that is designed for minimally invasive medical procedures, according to one embodiment. 
         FIG. 2  illustrates another view of the electrosurgical medical instrument shown in  FIG. 1 . 
         FIG. 3  illustrates another view of the electrosurgical medical instrument shown in  FIG. 1 . 
         FIG. 4  illustrates a sectional view of the electrosurgical medical instrument illustrating elements thereof contained within a housing, according to one embodiment. 
         FIG. 5  illustrates a partial sectional view of the electrosurgical medical instrument in a locked out position to prevent the actuation of the control lever, according to one embodiment. 
         FIG. 6  illustrates a partial sectional view of the electrosurgical medical instrument in a full stroke position, according to one embodiment. 
         FIG. 7  illustrates the electrosurgical medical instrument comprising an initialization clip interfering with the handle, according to one embodiment. 
         FIG. 8  is another view of the electrosurgical medical instrument comprising an initialization clip as shown in  FIG. 7 , according to one embodiment. 
         FIG. 9  illustrates a sectional view of a housing portion of an electrosurgical medical instrument showing an electronic circuit device portion of an electronics system, according to one embodiment. 
         FIG. 10  illustrates a second electronic substrate comprising an inductor and a transformer that form a part of the RF energy circuit, according to one embodiment. 
         FIG. 11  illustrates two separate substrates provided where the digital circuit elements are located on a first substrate and the RF amplifier section and other analog circuit elements are located on a second substrate, according to one embodiment. 
         FIG. 12  illustrates a partial cutaway view of a housing to show an electrical contact system, according to one embodiment. 
         FIG. 13  illustrates a partial cutaway view of a housing to show an electrical contact system and an inner sheath removed, according to one embodiment. 
         FIG. 14  illustrates a partial cutaway view of a housing with an electrically conductive shaft removed to show an electrical contact element, according to one embodiment. 
         FIG. 15  illustrates a partial sectional view of the electrosurgical medical instrument in a locked position, according to one embodiment. 
         FIG. 16  illustrates another partial sectional view of the electrosurgical medical instrument in a locked position, according to one embodiment. 
         FIG. 17  illustrates another partial sectional view of the electrosurgical medical instrument with an activation button partially depressed to activate the energy circuit without releasing the knife lockout mechanism, according to one embodiment. 
         FIG. 18  illustrates another partial sectional view of the electrosurgical instrument with the activation button fully depressed to activate the energy circuit and release the knife lockout mechanism, according to one embodiment. 
         FIG. 19  illustrates another partial sectional view of the electrosurgical medical instrument with the activation button fully depressed to activate the energy circuit with the knife lockout mechanism released and the knife fully thrown, according to one embodiment. 
         FIG. 20  is a perspective view of an initialization clip, according to one embodiment. 
         FIG. 21  is a partial cutaway view of the initialization clip shown in  FIG. 20 , according to one embodiment. 
         FIG. 22  illustrates an RF drive and control circuit, according to one embodiment. 
         FIG. 23  illustrates a perspective view of one embodiment of a transformer employed in the RF drive circuit illustrated in  FIG. 22 . 
         FIG. 24  illustrates a perspective view of one embodiment of a primary coil of the transformer illustrated in  FIG. 23 . 
         FIG. 25  illustrates a perspective view of one embodiment of a secondary coil of the transformer illustrated in  FIG. 23 . 
         FIG. 26  illustrates a bottom view of the primary coil illustrated in  FIG. 24 . 
         FIG. 27  illustrates a side view of the primary coil illustrated in  FIG. 24 . 
         FIG. 28  illustrates a sectional view of the primary coil illustrated in  FIG. 24  taken along section  28 - 28 . 
         FIG. 29  illustrates a bottom view of the secondary coil illustrated in  FIG. 25 . 
         FIG. 30  illustrates a side view of the secondary coil illustrated in  FIG. 25 . 
         FIG. 31  illustrates a sectional view of the secondary coil illustrated in  FIG. 30  taken along section  31 - 31 . 
         FIG. 32  illustrates a perspective view of an inductor employed in the RF drive circuit illustrated in  FIG. 22 . 
         FIG. 33  illustrates a bottom view of the inductor illustrated in  FIG. 32 . 
         FIG. 34  illustrates a side view of the inductor illustrated in  FIG. 32 . 
         FIG. 35  illustrates a sectional view of the inductor illustrated in  FIG. 34  taken along section  35 - 35 . 
         FIG. 36  illustrates main components of a controller, according to one embodiment. 
         FIG. 37  is a signal plot illustrating the switching signals applied to a field effect transistor (FET), a sinusoidal signal representing the measured current or voltage applied to a load, and the timings when a synchronous sampling circuit samples the sensed load voltage and load current, according to one embodiment. 
         FIG. 38  illustrates a drive waveform for driving an FET gate drive circuit, according to one embodiment. 
         FIG. 39  illustrates a diagram of a digital processing system located on a first substrate, according to one embodiment. 
         FIG. 40  illustrates a battery discharge circuit, according to one embodiment. 
         FIG. 41  illustrates a RF amplifier section with an output sensing test circuit and magnetic switch element, according to one embodiment. 
         FIG. 42  illustrates a fused battery connected to a substrate-mounted FET, according to one embodiment. 
         FIG. 43  illustrates a fused battery connected to a substrate-mounted control relay, according to one embodiment. 
         FIG. 44  illustrates a potted fused battery connected to a substrate-mounted FET, according to one embodiment. 
         FIG. 45  illustrates a potted fused battery connected to a substrate-mounted control relay, according to one embodiment. 
         FIG. 46  illustrates a potted fused battery including a reed relay and control FET, according to one embodiment. 
         FIG. 47  illustrates a potted fused battery including a reed relay and control relay, according to one embodiment. 
         FIGS. 48A and 48B  represent a flow diagram of a process for initializing a medical instrument fitted with an initialization clip, according to one embodiment. 
         FIGS. 49-57  illustrates the ornamental design for a surgical instrument handle assembly as shown and described, according to one embodiment, where: 
         FIG. 49  is a left perspective view of a handle assembly for a surgical instrument. 
         FIG. 50  is a right perspective view thereof. 
         FIG. 51  is a left perspective view thereof. 
         FIG. 52  is a left view thereof. 
         FIG. 53  is a front view thereof. 
         FIG. 54  is a right view thereof. 
         FIG. 55  is a rear view thereof. 
         FIG. 56  is a top view thereof. 
         FIG. 57  is a bottom view thereof. 
     
    
    
     DESCRIPTION 
     Before explaining various embodiments of medical instruments in detail, it should be noted that the illustrative embodiments are not limited in application or use to the details of construction and arrangement of parts illustrated in the accompanying drawings and description. The illustrative embodiments may be implemented or incorporated in other embodiments, variations and modifications, and may be practiced or carried out in various ways. Further, unless otherwise indicated, the terms and expressions employed herein have been chosen for the purpose of describing the illustrative embodiments for the convenience of the reader and are not for the purpose of limitation thereof. 
     Further, it is understood that any one or more of the following-described embodiments, expressions of embodiments, examples, can be combined with any one or more of the other following-described embodiments, expressions of embodiments, and examples. 
     The present disclosure is directed generally to medical instruments and in particular, although not exclusively, to electrosurgical instruments. The present disclosure also is directed to drive circuits and methods for driving such medical instruments. Additionally, the present disclosure is directed to lockout mechanisms, user interfaces, initialization techniques, and battery power conservation circuits and methods for such surgical instruments. 
     For clarity of disclosure, the terms “proximal” and “distal” are defined herein relative to a surgeon grasping the electrosurgical instrument. The term ‘proximal” refers the position of an element closer to the surgeon and the term “distal” refers to the position of an element further away from the surgeon. 
     Many surgical procedures require cutting or ligating blood vessels or other vascular tissue. With minimally invasive surgery, surgeons perform surgical operations through a small incision in the patient&#39;s body. As a result of the limited space, surgeons often have difficulty controlling bleeding by clamping and/or tying-off transected blood vessels. By utilizing electrosurgical forceps, a surgeon can cauterize, coagulate/desiccate, and/or simply reduce or slow bleeding by controlling the electrosurgical energy applied through jaw members of the electrosurgical forceps, otherwise referred to as clamp arms. 
       FIG. 1  illustrates the form of an electrosurgical medical instrument  100  that is designed for minimally invasive medical procedures, according to one embodiment. As shown, the instrument  100  is a self contained device, having an elongate shaft  102  that has a housing  112  with a handle  104  connected to the proximal end of the shaft  102  and an end effector  106  connected to the distal end of the shaft  102 . In this embodiment, the end effector  106  comprises medical forceps  108  having a movable jaw member and a cutting blade or knife (not shown) coupled to an inner sheath (not shown) located within the shaft  102  that are controlled by the user manipulating a control lever  110  (e.g., hand trigger) portion of the handle  104 . In the illustrated embodiment, the control lever  110  (e.g., hand trigger) is in the form of a hook (e.g., shepherd&#39;s hook) having a curved front portion and a rear portion where the rear portion extends below the front portion. The curved front portion and the rear portion define an aperture therebetween to receive the user&#39;s hand to operate the control lever  110 . During a surgical procedure, the shaft  102  is inserted through a trocar to gain access to the patient&#39;s interior and the operating site. 
     The surgeon will manipulate the forceps  108  using the handle  104 , the control lever  110 , and rotation knob  116  until the forceps  108  are located around the vessel to be cauterized. The rotation knob  116  is coupled to the shaft  102  and the end effector  106 . Rotation of the rotation knob  116  causes rotation of the shaft  102  and the end effector  106 . In one embodiment, the shaft  102  is continuously rotatable greater than 360° using the rotation knob  116 . To perform the desired cauterization Electrical energy at an RF frequency (it has been found that frequencies above about 50 kHz (e.g., ˜100 kHz and higher) do not affect the human nervous system) is then applied by, in a controlled manner, to the forceps  108  by actuating an activation button  114 . The activation button  114  has a partial activation position and a full activation position. 
     As shown in  FIG. 1 , in this embodiment, the handle  104  houses batteries and the housing houses control electronics for generating and controlling the electrical energy required to perform the cauterization. In this way, the instrument  100  is self contained in the sense that it does not need a separate control box and supply wire to provide the electrical energy to the forceps  108 . The instrument  100  also comprises a first visual feedback element  118   a  on the proximal end of the housing  112  to indicate that the device is ready for use and functioning normally, that there are a limited number of transections remaining, that RF energy is being delivered, that an alert condition or fault exists, that the initialization clip was removed, among other indications. In one embodiment, the first visual feedback element  118   a  is a light emitting diode (LED), without limitation. In one embodiment, the first visual feedback element  118   a  is a tri-color LED. In one embodiment, the instrument  100  comprises an integral generator and a non-reusable battery. 
       FIG. 2  illustrates another view of the electrosurgical medical instrument  100  shown in  FIG. 1 . In one embodiment, the instrument  100  comprises a second visual feedback element  118   b  located on the proximal end of the housing  112 . In one embodiment, the second visual feedback element  118   b  performs the same function as the first visual feedback element  118   a . In one embodiment, the second visual feedback element  118   b  is an LED, without limitation. In one embodiment, the second visual feedback element  118   b  is a tri-color LED. 
       FIG. 3  illustrates another view of the electrosurgical medical instrument  100  shown in  FIG. 1 . In one embodiment, the instrument  100  comprises a disposal button  120  located on the bottom of the handle  104 , for example. The disposal button  120  is used to deactivate the instrument  100 . In one embodiment, the instrument  100  may be deactivated by pushing and holding the disposal button  120  for a predetermined period. For example, the instrument  100  may be deactivated by pushing and holding the disposal button  120  for about four seconds. In one embodiment, the instrument  100  will automatically deactivate after a predetermined period. For example, the instrument  100  will automatically deactivate either eight or 10 hours after completion of the first cycle. An aperture  115  formed in the handle  104  provides a path for audio waves or a means for sound generated by an audio feedback element such as a piezoelectric buzzer to escape, for example, from within the handle  104 . In one embodiment, the piezoelectric buzzer operates at 65 dBa at one meter at a frequency between about 2.605 kHz to 2.800 kHz, for example. The aperture  115  enables the sound to escape the handle  104  so that it is comfortably audible to the surgeon while operating the medical instrument  100 . 
       FIG. 4  illustrates a sectional view of the electrosurgical medical instrument  100  illustrating elements thereof contained within the housing  112 , according to one embodiment. In one embodiment, the instrument  100  comprises a knife lockout mechanism  200  to prevent the advancement of an inner sheath  202 , which is coupled to a blade (not shown) portion of the medical forceps  108 . In the illustrated embodiments, the medical forceps  108  having a movable jaw member that is pivotally movable to clamp down on a vessel when the control lever  110  is squeezed proximally in the direction of arrow  122 . The cutting blade or knife (not shown) portion of the medical forceps  108  also advances distally when the control lever  110  is squeezed proximally. The cutting blade, sometime referred to as the knife, is for cutting the vessel after it has been cauterized. To prevent a “cold cut” of the vessel, which is defined as cutting with no application of energy to the vessel, a knife lockout mechanism  200  prevents the control lever  110  from being squeezed and thus prevents the blade from being advanced until the activation button  114  is fully engaged and a suitable amount of RF energy is applied to the vessel to properly cauterize it. 
     The knife lockout mechanism  200  ensures that the activation button  114  is fully depressed to activate the RF energy source such that energy is delivered to the vessel prior to cutting. When the activation button  114  is fully engaged, the knife lockout mechanism  200  enables the control lever  110  to be squeezed proximally in the direction of arrow  122 . This action advances the inner sheath  202  distally to close the jaw members of the electrosurgical forceps  108  while the cutting blade is simultaneously advanced to cut the vessel after it is fully cauterized. Therefore, electrosurgical energy is applied to the vessel through the jaw members of the electrosurgical forceps  108  before the cutting blade advances. 
     Also shown in  FIG. 4  is an integral energy source  300 , according to one embodiment. In the embodiment illustrated in  FIG. 4 , the integral energy source  300  may be a non-replaceable DC energy source such as a battery  300  that fits within the handle portion  104  of the housing  112 . One embodiment of the energy source  300  is described in more detail hereinbelow. 
     In one embodiment, the battery  300  is a 1000 mAh, triple-cell Lithium Ion Polymer battery, Lithium battery, among others. The battery  300  will be fully charged prior to Ethylene Oxide (EtO) sterilization, and will have a fully charged voltage of about 12V to about 12.6V. The battery  300  will have two 20 A fuses fitted to the substrate which connects the cells, one in line with each terminal. In other embodiments, the battery capacity may be greater than 1000 mAh, such as, up to about 3000 mAh, for example. 
     In one embodiment, the minimum distance between terminals of the battery  300  may be about 3 mm such that sparking conditions require an atmosphere with a dielectric breakdown of 4200V/m. Even at the lowest pressures encountered in an EtO cycle, for a condition of pure EtO, across a 3 mm gap the breakdown voltage is approximately 450V. This is more than an order of magnitude greater than the maximum battery voltage, and this is further mitigated by the use of a Nitrogen blanket during the sterilization process. 
     Also shown in  FIG. 4  is an electronics system  400 , according to one embodiment. In one embodiment, the electronics system  400  comprises an RF generation circuit to generate an RF drive signal and to provide the RF drive signal to the at least one electrical contact where the RF generation circuit also includes a resonant circuit. The electronics system  400  also comprises control elements such as one or more than one microprocessor (or micro-controller) and additional digital electronic elements to control the logical operation of the instrument  100 . One embodiment of the electronics system  400  is described hereinbelow. The electronics system  400  including the RF generation circuit is supported by the housing  112 . In one embodiment, RF generation circuit to generate an RF drive signal is integral to the housing  112  and the battery  300  is non-reusable. 
     Also referenced in  FIG. 4  is a logical lockout mechanism  500 , in accordance with one embodiment. The logical lockout mechanism works in cooperation with an initialization clip  600  (see  FIGS. 7-9 ) and  650  (see  FIGS. 20-21 ) to prevent operation of the instrument  100  until it is removed. One embodiment of the logical lockout mechanism  500  is described hereinbelow. 
       FIG. 5  illustrates the electrosurgical medical instrument  100  in a locked out position to prevent the actuation of the control lever  110 , according to one embodiment. The control lever  110  comprises a trigger lever  212  portion that is configured to rotate about a trigger pivot  214  when the control lever  110  is squeezed in the direction of arrow  122  ( FIG. 4 ), unless the instrument is in locked out mode. 
     In the locked out mode, the trigger lever  212  portion of the control lever  110  is prevented from rotating about the trigger pivot  214  because a projection  218  of the trigger lever  212  engages a top surface  216  of an activation button lever  234  that rotates about activation button pivot  232  when the activation button  114  is squeezed in the direction of arrow  220 . A contact button torsion spring  224  keeps the activation button  114  in an outwardly position to disable the electrosurgical energy from being applied while simultaneously engaging the projection  218  of the trigger lever  212  with the top surface  216  to lockout the instrument  100  until the activation button  114  is fully engaged in the direction of arrow  220 . 
     A second trigger lever  210  comprises a first end that defines a pin slot  206  and a second end that defines a tab  226 . The pin slot  206  engages a pin  208  portion of the trigger lever  212 . As the trigger lever  212  rotates in the direction of arrow  236  about trigger pivot  214  the pin  208  moves within the pin slot  206  to apply a rotation movement to the second trigger lever  210 . The tab  226  engages an aperture  228  to mechanically couple the second trigger lever  210  to the inner sheath  202 . Thus, as the trigger lever  212  moves in the direction of arrow  236 , the second trigger lever  210  rotates about lever pivot  204  to apply a linear translation motion to the inner sheath  202  in the direction of arrow  238 . A trigger torsion spring  222  engages the second trigger lever  210  at a notch  240  formed on the second trigger lever  210 . The trigger torsion spring  222  torque balances the hand force applied to the second trigger lever  210  through the control lever  110  about the trigger pivot  214 . 
       FIG. 6  illustrates the electrosurgical medical instrument  100  in a full stroke position, according to one embodiment. In order to release the lockout mechanism  200 , the activation button  114  is fully engaged in the direction of arrow  220  to cause the activation button lever  234  to rotate about activation button pivot  232  and release the top surface  216  from engaging the projection  218 . This allows the projection  218  to slidably rotate past a surface  230  of the activation button lever  234  as the trigger lever  212  slidably rotates in the direction of arrow  236  about trigger pivot  214  as the control lever  110  is squeezed, or actuated, proximally by the surgeon. During the control lever  110  actuation period, the pin  208  is engaged by the pin slot  206  slidably moving therein and rotating the second trigger lever  210  about the lever pivot  204 . As shown in  FIG. 6 , in the full stroke position, the inner sheath  202  is fully advanced in the distal direction in accordance with the translation motion applied by the tab  26  and aperture  228  as the second trigger lever  210  is fully rotated about the lever pivot  204 . Also of note, the trigger and contact button torsion springs  222 ,  224 , respectively, are torqued in order to return the control lever  110  and contact button  114 , respectively, to their normal locked out deactivated positions. 
       FIG. 7  illustrates the electrosurgical medical instrument  100  comprising an initialization clip  600 , according to one embodiment. The clip  600  prevents firing the medical instrument  100  without enabling and also provides some protection during shipment. The initialization clip  600  is applied to the instrument  100  after initialization at the factory and stays on the instrument  100  during storage. Upon removal of the clip  600 , the instrument  100  is enabled. In one embodiment, if the instrument  100  has completed one full energy activation cycle (described in more detail hereinbelow) and the clip  600  is re-installed, the instrument  100  will not function upon removal of the clip  600  a second time. 
     In addition to the clip  600 , other techniques for activating the battery  300  are contemplated by the present disclosure. In one embodiment, described but not shown, a “Pull Tab” may be employed to activate the battery  300 . In one embodiment, the Pull Tab may comprise a plastic strip that physically separates the battery contacts acting as an insulator. A multi-stage version of this embodiment enables production testing. 
     In another embodiment, described but not shown, a breakaway plastic tab may be employed to activate the battery  300 . In one embodiment, the breakaway plastic tab separates the battery  300  contacts and cannot be replaced. 
     In another embodiment, described but not shown, a mechanical mechanism may be employed to activate the battery  300 . In one embodiment, the mechanical mechanism may be activated from outside the battery  300  to open the battery  300  contacts via a mechanical means. 
     In another embodiment, described but not shown, a removable battery is provided, where the battery is removed prior to the sterilizing the medical instrument  100 . The removable battery may be sterilized using a separate sterilization method. For example, the medical instrument  100  may be sterilized by EtO and the battery by H 2 O 2  (hydrogen peroxide), e-beam sterilization, or any suitable sterilization technique that is non-destructive to the battery. 
     In another embodiment, described but not shown, a Hall-effect device may be employed as an activation means. The Hall-effect device is responsive to a magnetic field and can be used to detect the presence or absence of a magnetic field. 
     In yet another embodiment, a remotely activated switch element  606  (such as a reed relay, Hall-effect sensor, RF device, optical element, for example, see  FIGS. 8, 10, 41 ) that disables the electronics system  400  when a remote switch activation element  602  (such as, for example, a magnet as shown in  FIG. 8 , RF device, optical element) is brought into proximity to the magnetically operated element  606 . This particular embodiment is described in more detail hereinbelow in connection with  FIGS. 8, 10, 41, and 42-47 , for example. 
     Also shown in  FIG. 7  is the activation button  114  in multiple positions. In one embodiment, the activation button  114  is movable over multiple actuation positions to control multiple functions. In the embodiment illustrated in  FIG. 7 , the activation button  114  is shown in three separate positions  114   a ,  114   b ,  114   c , where in a first position  114   a  the activation button  114  is full extended distally outwardly and does not result in energizing the RF energy circuit. In a second position  114   b  the activation button  114  is in a partial depression mode and in a third position  114   c  the activation button  114  is in a full depression mode. During normal operation, e.g., when the clip  600  is removed, when the activation button is in the first position  114   a , the lockout mechanism is engaged and the operation of the control lever  110  is inhibited as previously described in connection with  FIGS. 4-6  and the energy source  300  ( FIG. 4 ) is disconnected from the electronics system  400  ( FIG. 4 ). When the activation switch  114  is partially depressed in the second position  114   b , the device is still mechanically locked out to inhibit the operation of the control lever  110 , as previously described in connection with  FIGS. 4-6 , but the circuit is connected to the energy source  300  and becomes partially functional. For example, in one embodiment, several logic functions may be enabled while keeping the RF energy activation circuit disabled. When the activation switch  114  is fully depressed in the third position  114   c , the device is mechanically unlocked and enables the operation of the control lever  110 , as previously described in connection with  FIGS. 4-6 , but the circuit is connected to the energy source  300  and becomes fully functional, including enabling the operation of the logic and the RF energy circuit. It will be appreciated, however, that in the configuration of the instrument  100  shown in  FIG. 7 , the clip  600  mechanically prevents the operation of the control lever  110  and also inhibits the operation of the electronics system  400  by electrically disconnecting the energy source  300  from the electronics system  400 . The functionality of the multi-position activation button  114  as it relates to the mechanical and electrical lockout will be described in more detail hereinbelow. 
       FIG. 8  is another view of the electrosurgical medical instrument  100  comprising an initialization clip  600  as shown in  FIG. 7 , according to one embodiment. In  FIG. 7 , the clip  600  is shown without a cover plate to show the internal structure of the clip  600 . As shown in  FIG. 8 , the clip  600  defines an internal cavity that contains a magnet  602 . The magnetic flux generated by the magnet  602  acts on a magnetically operated element  606  located on the electronics system  400 . The magnetically operated element  606  is coupled to the electronics system  400  and the energy source  300  and acts as a switch to disconnect and connect the energy source to the electronics system  400 . 
     In the embodiment illustrated in  FIG. 8 , the magnetic flux generated by the magnet  602  causes the magnetically operated element  606  to electrically disconnect the energy source  300  from the electronics system  400 , including a transformer  404  and an inductor  406 . When the magnet  602  is removed, by removing the clip  600  from the instrument  100 , for example, the magnetically operated element  606  electrically connects the energy source  300  to the electronics system  400 . Accordingly, as long as the clip  600  with the magnet  602  is located on the instrument  100 , the instrument  100  is mechanically and electrically locked out. As previously described, when the clip  600  is located on the instrument  100 , depressing the  114  in the first position  114   a , second position  114   b , or third position  114   c  does not activate the electronics system  400  because the magnetically operated element  606  electrically disconnects or decouples the energy source  300  from the electronics system  400 . In one embodiment, the magnetically operated element  606  may be a reed switch, a hall-effect sensor, or any other switch type device that can be activated by a magnetic field. Still, in another embodiment, the medical instrument  100  may comprise an accelerometer to detect motion. When the accelerometer is at rest, indicating that the medical instrument  100  is at rest, the instrument  100  is completely powered down by disconnecting the battery  300  from the electronics system  400 . When the accelerometer detects motion, indicating that the medical instrument  100  is no longer at rest, the instrument is powered up by connecting the battery  300  to the electronic system  400 . 
     While undergoing sterilization, the electronics system  400  will not be powered and will draw only a leakage current of about 1 pA. The electronics system  400  may be disabled by the magnetically operated element  606  (e.g., a reed switch) and magnet  602  which is encased in the clip  600 . The clip  600  is fitted to the medical instrument  100  as part of the manufacturing process, and must be removed to enable power from the battery  300 . When powered, in the idle condition the load circuit draws an average of 10 mA, with peaks of up to 65 mA. When the activation button  114  is pressed, the device draws an average of 5 A, with peaks of 15.5 A from the battery  300 . When packaged, the jaws are closed and there is no material between them. In one non-limiting embodiment, the voltage generated across the jaws is a maximum of 85V rms. This arrangement means there are two methods for preventing the generation of high voltages or currents—the magnetic clip  600  is the primary disabling mechanism, and the activation button  114  is the second. Several connection options for the battery  300  are described herein below with reference to  FIGS. 42-47 . 
     Mechanical fastening elements  604  and  608  are used to hold the clip  600  coupled to the medical instrument  100 . In the embodiment illustrated in  FIG. 8 , the clip comprises a first half  612   a  and a second  612   b  that can be fastened using mechanical fastening elements to form an interference fit, press fit, or friction fit, such that friction holds the two halves  612   a, b  after they are pushed or compressed together. In other embodiments, other fastening techniques may be employed to fasten the two halves  612   a, b  such as by ultrasonic welding, snap fitting, gluing, screwing, riveting, among others. Another embodiment of an initialization clip  650  is described below in connection with  FIGS. 20 and 21 . 
       FIG. 9  illustrates a sectional view of the housing  112  portion of the electrosurgical medical instrument  100  showing an electronic circuit device  402  portion of the electronics system  400 , according to one embodiment. In one embodiment, the electronic circuit device  402  can be configured as a data gathering/programming interface, for example. In one embodiment, the electronic circuit device  402  can be programmed by a programming device (not shown). The electronic circuit device  402  can output real-time data such as tissue voltage, current, and impedance to an external data recording device (not shown). In one embodiment, the electronic circuit device  402  is a non-volatile memory device that can store computer program instructions and/or tissue voltage, current, and impedance data. 
     In one embodiment, the data transfer/device programming function can be implemented by a connector provided on the housing  112  to couple an external data transfer/device programmer device to the electronic circuit device  402 . The external data transfer/device programmer device may be employed for two-way communication with the electronic circuit device  402 . To upload a new program to the medical instrument  100 , for example, the external data transfer/device programmer device can be plugged into the connector to couple to the electronic circuit device  402  and then upload the program. Data stored in the electronic circuit device  402  could be read just as easily via the connector. The data may include, for example, voltage (V), current (I), impedance (Z), device parameters, among others, without limitation. 
     In one embodiment, the data transfer/device programming function can be implemented via at least one of the LED  118   a, b  interfaces. For example, either through the tri-color LEDs  118   a, b  or the addition of an infrared (IR) LED (not shown), an optical data interface can be implemented. The optical data interface can be employed to transfer data to and from the instrument  100  and/or program the instrument  100 . In one embodiment, a separate hood (not shown) comprising a cavity to receive the proximal end of the housing  112  comprising the LEDs  118   a, b  may be provided. The hood also comprises optical elements (e.g., IR LEDs) configured for optical communication in order to communicate via the optical interface comprised of LEDs  118   a, b . In operation, the hood may be slidably inserted over the proximal end of the housing  112  such that the LEDs  118   a, b  are optically aligned with the optical elements located inside the hood. 
       FIGS. 10 and 11  illustrate the electrosurgical medical instrument  100  without the housing  112  portion to reveal the internal components of the instrument  100 , according to one embodiment. The electronics system  400  comprises both digital and RF analog circuit elements. Accordingly, as shown in  FIG. 11 , two separate substrates  408   a  and  408   b  are provided where the digital circuit elements are located on a first substrate  408   a  and the RF amplifier section and other analog circuit elements are located on a second substrate  408   b . The first and second substrates  408   a, b  are interconnected by a interconnect device  412 . Still in  FIG. 11 , the first substrate  408   a  also includes digital circuit components including, for example, the electronic circuit device  402  for storing program and tissue information. The first substrate  408   a  also includes an audio feedback element  410 . In one embodiment, the audio feedback element  410  is a piezo device. In other embodiments, however, different types of audio feedback devices may be employed without limitation. It will be appreciated that in various embodiments, the first and second substrates  408   a, b  are formed of printed circuit boards. In other embodiments, however, these substrates can be formed of any suitable materials, such as alumina ceramics, for example. The substrates  408   a, b  may comprise discrete, integrated, and/or hybrid circuit elements and combinations thereof. With reference now to  FIG. 10 , the second electronic substrate  408   b  comprises an inductor  404  and a transformer  406  that form a part of the RF energy circuit. With reference now to the embodiments disclosed in  FIGS. 10 and 11 , also shown are the dual tri-color LEDs  118   a, b . Also shown is the electrical contact system  700  that couple RF energy produced by the RF energy circuits on the second substrate  408   b  to the medical forceps  108  ( FIGS. 1 and 2 ). An electrical conductor  702  is coupled to the electrical contact system  700 . The other end of the electrical conductor  702  is coupled to the RF energy circuit. 
       FIGS. 12-14  illustrate various views of the electrical contact system  700 , according to one embodiment.  FIG. 12  illustrates a partial cutaway view of the housing  112  to show the electrical contact system  700 , according to one embodiment. The electrical contact system  700  comprises an electrically conductive shaft  716  that is rotatable over 360° and comprises first and second rotatable electrodes  706 ,  708 . The rotatable electrodes  706 ,  708  are electrically coupled to corresponding first and second electrical contact elements  704   a ,  704   b  where the electrical contact elements  704   a, b  are electrically coupled to the electrical conductor  702  ( FIGS. 10-11 ) coupled to the RF energy circuit. Each the first and second electrical contact elements  704   a ,  704   b  comprise first and second electrical contact points  710   a ,  710   b  and  712   a ,  712   b . The electrical contact points  710   a  and  712   a  are electrically coupled to a side wall  718  of the first rotatable electrode  706  and the electrical contact points  710   b  and  712   b  are electrically coupled to a side wall  720  of the second rotatable electrode  708 . In one embodiment, the two electrical contact elements  704   a, b  provide four contact points  710   a ,  712   a ,  710   b ,  712   b  for redundancy. The electrical contact elements  704   a, b  and corresponding four contact points  710   a ,  712   a ,  710   b ,  712   b  allow the rotatable electrodes  706 ,  708  of the electrically conductive shaft  716  to rotate over 360°. The two electrical contact elements  704   a, b  may be formed of any suitable electrically conductive element such as copper, aluminum, gold, silver, iron, and any alloy including at least one of these element, without limitation. In one embodiment, the two electrical contact elements  704   a, b  are formed of beryllium copper (BeCu) and are gold plated for corrosion resistance and good electrical contact properties. In  FIG. 12  the inner sheath  202  is shown slidably inserted within the electrically conductive shaft  716 . 
       FIG. 13  illustrates a partial cutaway view of the housing  112  to show the electrical contact system  700  and the inner sheath  202  removed, according to one embodiment.  FIG. 13 , also shows an electrical element  714  that is electrically coupled to the electrical conductor  702  ( FIGS. 10-11 ) coupled to the RF energy circuit. The electrical element  714  is coupled to the electrical contact elements  704   a, b . Accordingly, the RF energy circuit is coupled to the electrical contact element  704   a, b.    
       FIG. 14  illustrates a partial cutaway view of the housing  112  with the electrically conductive shaft  716  removed to show the electrical contact element  714 , according to one embodiment. As shown in  FIG. 14 , the electrical contact element  714  is located in a partial circular wall  724  that separates the circular cavities  722 ,  726  configured to rotatably receive the respective rotatable electrodes  706 ,  708  ( FIGS. 12-13 ). The electrical contact element  714  is electrically coupled to the two electrical contact elements  704   a, b . As shown, the two electrical contact elements  704   a, b  are located on top of the electrical contact element  714 . 
       FIG. 15  illustrates a partial sectional view of the electrosurgical medical instrument  100  in a locked position, according to one embodiment.  FIG. 15  illustrates the electrosurgical medical instrument  100  in a locked out position to prevent the actuation of the control lever  110 , according to one embodiment. The control lever  110  comprises a trigger lever  212  portion that is configured to rotate about a trigger pivot  214  when the control lever  110  is squeezed in the direction of arrow  122  ( FIG. 4 ), unless the instrument is in locked out mode. 
     In the locked out mode, the trigger lever  212  portion of the control lever  110  is prevented from rotating about the trigger pivot  214  because a projection  218  of the trigger lever  212  engages a top surface  216  of an activation button lever  234  that rotates about activation button pivot  232  when the activation button  114  is squeezed in the direction of arrow  220 . A contact button torsion spring  224  keeps the activation button  114  in an outwardly position to disable the electrosurgical energy from being applied while simultaneously engaging the projection  218  of the trigger lever  212  with the top surface  216  to lockout the instrument  100  until the activation button  114  is fully engaged in the direction of arrow  220 . 
     A second trigger lever  210  comprises a first end that defines a pin slot  206  and a second end that defines a tab  226 . The pin slot  206  engages a pin  208  portion of the trigger lever  212 . As the trigger lever  212  rotates in the direction of arrow  236  about trigger pivot  214  the pin  208  moves within the pin slot  206  to apply a rotation movement to the second trigger lever  210 . The tab  226  engages an aperture  228  to mechanically couple the second lever to the inner sheath  202 . Thus, as the trigger lever  212  moves in the direction of arrow  236 , the second trigger lever  210  rotates about lever pivot  204  to apply a linear translation motion to the inner sheath  202  in the direction of arrow  238 . A trigger torsion spring  222  engages the second trigger lever  210  at a notch  240  formed on the second trigger lever  210 . The trigger torsion spring  222  torque balances the hand force applied to the second trigger lever  210  through the control lever  110  about the trigger pivot  214 . 
       FIG. 16  illustrates another partial sectional view of the electrosurgical medical instrument  100  in a locked position, according to one embodiment. In the locked position, the knife lockout mechanism  200  prevents the control lever  110  from rotating about the trigger pivot  214  when the projection  218  of the trigger lever  212  engages a top surface  216  of the activation button lever  234 . The activation button lever  234  rotates about the activation button pivot  232  when the activation button  114  is squeezed or depressed in the direction of arrow  220 . The activation button  114  is supported independently from the activation button pivot  232  by a mechanism  254  such that the activation button  114  is independently operable from the actuation of the control lever  110  actuate the cutting blade (knife). Thus, the activation button  114  can be depressed to energize the instrument  100  without actuating the cutting blade (knife). When the activation button  114  is squeezed or depressed in the direction of arrow  220 , the activation button  114  actuates a switch  250 , which enables energy actuation of the instrument  100 . Thus, electrosurgical RF energy is applied through jaw members of the electrosurgical forceps, otherwise referred to as clamp arms of the instrument  100 . The cutting blade, however, is still locked out by the knife lockout mechanism  200 . A tang  252  prevents the activation button  114  from being removed by pulling forward on it. 
       FIG. 17  illustrates another partial sectional view of the electrosurgical medical instrument  100  with the activation button  114  partially depressed to activate the energy circuit without releasing the knife lockout mechanism  200 , according to one embodiment. Although the activation button  114  is partially depressed to actuate the switch  250  and energize the instrument  100 , but the knife lockout mechanism  200  is still engaged to prevent the knife from being actuated by the control lever  110 . As shown, the projection  218  of the trigger lever  212  is still engaged with the top surface  216  of the activation button lever  234  to prevent the trigger lever  212  from rotating about the trigger pivot  214  when the control lever  110  is squeezed. 
       FIG. 18  illustrates another partial sectional view of the electrosurgical instrument  100  with the activation button  114  fully depressed to activate the energy circuit and release the knife lockout mechanism  200 , according to one embodiment. The activation button  114  is fully depressed to actuate the switch  250  and energize the instrument  100  and also releasing the knife lockout mechanism  200 . In the fully depressed mode, the activation button  114  rests on a pin  256 . As shown, the projection  218  of the trigger lever  212  is disengaged from the top surface  216  of the activation button lever  234  that rotates about activation button pivot  232  to enable the trigger lever  212  to rotate about the trigger pivot  214  when the control lever  110  is squeezed to throw the knife. As shown, the inner sheath  202  can now be advanced in the direction indicated by the direction of arrow  238 . 
       FIG. 19  illustrates another partial sectional view of the electrosurgical medical instrument  100  with the activation button  114  fully depressed to activate the energy circuit with the knife lockout mechanism  200  released and the knife fully thrown, according to one embodiment. As shown, the inner sheath  202  has advanced in the direction indicated by the direction of arrow  238 . 
       FIG. 20  is a perspective view of an initialization clip  650 , according to one embodiment. The initialization clip  650  is similar to the initialization clip  600  described in connection with  FIGS. 7-9 .  FIG. 21  is partial cutaway view of the initialization clip  650  shown in  FIG. 20 , according to one embodiment. With reference to  FIGS. 20 and 21 , the initialization clip  650  is attached to the electrosurgical medical instrument  100  to prevent firing the medical instrument  100  without enabling and also provides some protection during shipment. The initialization clip  650  is applied to the instrument  100  after initialization at the factory and stays on the instrument  100  during storage. Upon removal of the clip  650 , the instrument  100  activates in the manner described with respect to the initialization clip  600  of  FIGS. 6-9 . In one embodiment, if the instrument  100  has completed one full energy activation cycle (described in more detail hereinbelow) and the clip  650  is re-installed, the instrument  100  will not function upon removal of the clip  650  a second time. The initialization clip  650  comprises a snap button  652  to secure the clip  650  to the instrument  100  and a tilted magnetic pocket  654 . The magnetic pocket  654  contains a magnet that works in conjunction with a reed switch, or other suitable sensing element, to detect the presence of the initialization clip  650 , and thus determine whether it is attached or removed from the instrument  100 . In other respects, the initialization clip  650  operates similarly to the initialization clip  600  described in connection with  FIGS. 7-9 . 
     The description now turns to the RF drive and control circuitry sections of the battery powered electrosurgical instrument  100 , according to one embodiment. As described in  FIGS. 10-11 , the RF drive and control circuitry sections of the electronics system  400  are located on a second substrate  408   b . The electronics elements of the power supply and RF amplifier sections should be designed to have the highest efficiency possible in order to minimize the heat rejected into the relatively small handheld housing  112 . Efficiency also provides the longest storage and operational battery life possible. As described in the embodiments illustrated in  FIGS. 23-35 , litz wire may be wound around a bobbin core to reduce AC losses due to high frequency RF. The litz wire construction provides greater efficiency and thus also prevents heat generation in the device. 
     In various embodiments, efficiency of the power supply and RF drive and control circuitry sections also may minimize the size of the battery  300  required to fulfill the mission life, or to extend the mission life for a given size battery  300 . In one embodiment, the battery  300  provides a low source impedance at a terminal voltage of 12.6V (unloaded) and a 1030 mA-Hour capacity. Under load, the battery voltage is a nominal 11.1V, for example. 
     Radio frequency drive amplifier topologies may vary according to various embodiments. In one embodiment, for example, a series resonant approach may be employed where the operating frequency is varied to change the output voltage to force the medical instrument  100  to operate according to a pre-programmed load curve. In a series resonant approach, the impedance of a series resonant network is at a minimum at the resonant frequency, because the reactance of the capacitive and inductive elements cancel, leaving a small real resistance. The voltage maximum for a series resonant circuit also occurs at the resonant frequency (and also depends upon the circuit Q). Accordingly, to produce a high voltage on the output, the series resonant circuit should operate closer to the resonant frequency, which increases the current draw from the DC supply (e.g., battery  300 ) to feed the RF amplifier section with the required current. Although the series resonant approach may be referred to as a resonant mode boost converter, in reality, the design is rarely operated at the resonant frequency, because that is the point of maximum voltage. The benefit of a resonant mode topology is that if it is operated very close to the resonant frequency, the switching field effect transistors (FETs) can be switched “ON” or “OFF” at either a voltage or current zero crossing, which dissipates the least amount of power in the switching FETs as is possible. 
     Another feature of the RF drive and control circuitry section according to one embodiment, provides a relatively high turns ratio transformer which steps up the output voltage to about 85 VRMS from the nominal battery  300  voltage of about 11.1V. This provides a more compact implementation because only one transformer and one other inductor are required. In such a circuit, high currents are necessary on the transformer primary to create the desired output voltage or current. Such device, however, cannot be operated at the resonant frequency because allowances are made to take into account for the battery voltage dropping as it is expended. Accordingly, some headroom is provided to maintain the output voltage at the required level. A more detailed description of a series resonant approach is provided in commonly assigned international PCT Patent Application No. PCT/GB2011/000778, titled “Medical Device,” filed May 20, 2011, now International Application Publication No. WO 2011/144911, the disclosure of which is incorporated herein by reference in its entirety. 
     According to another embodiment, an RF instrument topology comprising a novel and unique architecture is provided for a handheld battery powered RF based generator for the electrosurgical medical instrument  100 . Accordingly, in one embodiment, the present disclosure provides an RF instrument topology with an architecture configured such that each power section of the device operate at maximum efficiency regardless of the load resistance presented by the tissue or what voltage, current, or power level is commanded by the controller. In one embodiment, this may be implemented by employing the most efficient modalities of energy transformation presently known and by minimizing the component size to provide a small and light weight electronics package to fit within the housing  112 , for example. 
     In one embodiment, the RF power electronics section of the electronics system  400  may be partitioned as a boost mode converter, synchronous buck converter, and a parallel resonant amplifier. According to one embodiment, a resonant mode boost converter section of the medical instrument  100  may be employed to convert the DC battery  300  voltage to a higher DC voltage for use by the synchronous mode buck converter. One aspect to consider for achieving a predetermined efficiency of the resonant mode boost converter section is ratio between input and output voltages of the boost converter. In one embodiment, although a 10:1 ratio is achievable, the cost is that for any appreciable power on the secondary the input currents to the boost mode transformer become quite heavy, in the range of about 15-25 A, depending on the load. In another embodiment a transformer turns ratio of about 5:1 is provided. It will be appreciated that transformer ratios in the range of about 5:1 to about 10:1 also may be implemented, without limitation. In a 5:1 transformer turns ratio, the design tradeoff is managing the Q of the parallel resonant output against the boost ratio. The resonant output network performs two functions. First, it filters the square, digital pulses from the Class D output amplifier and removes all but the fundamental frequency sine wave from the output. Second, it provides a passive voltage gain due to the Q of the filter network. In other words, current from the amplifier is turned into output voltage, at a gain determined by the circuit&#39;s unloaded Q and the load resistance, which affects the Q of the circuit. 
     Another aspect to consider for achieving a predetermined efficiency in the resonant mode boost converter section is to utilize a full bridge switcher topology, which allows half the turns ratio for the boost transformer for the same input voltage. The tradeoff is that this approach may require additional FET transistors, e.g., an additional two FETs are required over a half bridge approach, for example. Presently available switchmode FETs, however, are relatively small, and while the gate drive power is not negligible, it provides a reasonable design tradeoff. 
     Yet another aspect to consider for achieving a predetermined efficiency in the resonant mode boost converter section and operating the boost converter at maximum efficiency, is to always run the circuit at the resonant frequency so that the FETs are always switching at either a voltage or current minima, whichever is selected by the designer (ZCS vs. ZVS switching), for example. This can include monitoring the resonant frequency of the converter as the load changes, and making adjustments to the switching frequency of the boost converter to allow ZVS or ZCS (Zero Voltage Switching/Zero Current Switching) to occur for minimum power dissipation. 
     Yet another aspect to consider for achieving a predetermined efficiency in the resonant mode boost converter section is to utilize a synchronous rectifier circuit instead of a conventional full-wave diode rectifier block. Synchronous rectification employs FETs as diodes because the on-resistance of the FET is so much lower than that of even a Schottky power diode optimized for low forward voltage drop under high current conditions. A synchronous rectifier requires gate drive for the FETs and the logic to control them, but offers significant power savings over a traditional full bridge rectifier. 
     In accordance with various embodiments, the predetermined efficiency of a resonant mode boost converter is approximately 98-99% input to output, for example. Any suitable predetermined efficiency may be selected based on the particular implementation. Accordingly, the embodiments described herein are limited in this context. 
     According to one embodiment, a synchronous buck converter section of the medical instrument  100  may be employed to reduce the DC voltage fed to the RF amplifier section to the predetermined level to maintain the commanded output power, voltage or current as dictated by the load curve, with as little loss as is possible. The buck converter is essentially an LC lowpass filter fed by a low impedance switch, along with a regulation circuit to control the switch to maintain the commanded output voltage. The operating voltage is dropped to the predetermined level commanded by the main controller, which is running the control system code to force the system to follow the assigned load curve as a function of sensed tissue resistance. In accordance with various embodiments, the predetermined efficiency of a synchronous buck regulator is approximately 99%, for example. Any suitable predetermined efficiency may be selected based on the particular implementation. Accordingly, the embodiments described herein are limited in this context. 
     According to one embodiment, a resonant mode RF amplifier section comprising a parallel resonant network on the RF amplifier section output is provided. In one embodiment, a predetermined efficiency may be achieved by a providing a parallel resonant network on the RF amplifier section output. The RF amplifier section may be driven at the resonant frequency of the output network which accomplished three things. First, the high Q network allows some passive voltage gain on the output, reducing the boost required from the boost regulator in order to produce high voltage output levels. Second, the square pulses produced by the RF amplifier section are filtered and only the fundamental frequency is allowed to pass to the output. Third, a full-bridge amplifier is switched at the resonant frequency of the output filter, which is to say at either the voltage zero crossings or the current zero crossings in order to dissipate minimum power. Accordingly, a predetermined efficiency of the RF amplifier section is approximately 98%. Gate drive losses may limit the efficiency to this figure or slightly lower. Any suitable predetermined efficiency may be selected based on the particular implementation. Accordingly, the embodiments described herein are limited in this context. 
     In view of the RF instrument topology and architecture described above, an overall system efficiency of approximately 0.99*0.99*0.98, which is approximately 96%, may be achieved. Accordingly, to deliver approximately 45 W, approximately 1.8 W would be dissipated by the electronics exclusive of the power required to run the main and housekeeping microprocessors, and the support circuits such as the ADC and analog amplifiers and filters. To deliver approximately 135 W, approximately 5.4 W would be dissipated. This is the amount of power that would be required to implement a large jaw class generator in a hand held electrosurgical medical instrument. Overall system efficiency would likely only be a weak function of load resistance, instead of a relatively strong one as it may be the case in some conventional instruments. 
     In various other embodiments of the electrosurgical medical instrument  100 , a series resonant topology may be employed to achieve certain predetermined efficiency increase by employing a full bridge amplifier for the primary circuit and isolate the full bridge amplifier from ground to get more voltage on the primary. This provides a larger primary inductance and lower flux density due to the larger number of turns on the primary. 
       FIG. 22  illustrates an RF drive and control circuit  800 , according to one embodiment.  FIG. 22  is a part schematic part block diagram illustrating the RF drive and control circuitry  800  used in this embodiment to generate and control the RF electrical energy supplied to the forceps  108 . As will be explained in more detail below, in this embodiment, the drive circuitry  800  is a resonant mode RF amplifier comprising a parallel resonant network on the RF amplifier output and the control circuitry operates to control the operating frequency of the drive signal so that it is maintained at the resonant frequency of the drive circuit, which in turn controls the amount of power supplied to the forceps  108 . The way that this is achieved will become apparent from the following description. 
     As shown in  FIG. 22 , the RF drive and control circuit  800  comprises the above described battery  300  are arranged to supply, in this example, about 0V and about 12V rails. An input capacitor (C in )  802  is connected between the 0V and the 12V for providing a low source impedance. A pair of FET switches  803 - 1  and  803 - 2  (both of which are N-channel in this embodiment to reduce power losses) is connected in series between the 0V rail and the 12V rail. FET gate drive circuitry  805  is provided that generates two drive signals—one for driving each of the two FETs  803 . The FET gate drive circuitry  805  generates drive signals that causes the upper FET ( 803 - 1 ) to be on when the lower FET ( 803 - 2 ) is off and vice versa. This causes the node  807  to be alternately connected to the 12V rail (when the FET  803 - 1  is switched on) and the 0V rail (when the FET  803 - 2  is switched on).  FIG. 22  also shows the internal parasitic diodes  808 - 1  and  808 - 2  of the corresponding FETs  803 , which conduct during any periods that the FETs  803  are open. 
     As shown in  FIG. 22 , the node  807  is connected to an inductor-inductor resonant circuit  810  formed by an inductor L s    812  and an inductor L m    814 , which is the primary coil of a transformer  815 . The transformer  815  is the schematic symbol for the transformer  404  shown in  FIGS. 8 and 10  and described in more detail below in connection with  FIGS. 23-35 . Turning back to  FIG. 22 , the FET gate driving circuitry  805  is arranged to generate drive signals at a drive frequency (f d ) that opens and crosses the FET switches  803  at the resonant frequency of the parallel resonant circuit  810 . As a result of the resonant characteristic of the resonant circuit  810 , the square wave voltage at node  807  will cause a substantially sinusoidal current at the drive frequency (f d ) to flow within the resonant circuit  810 . As illustrated in  FIG. 22 , the inductor L m    814  is the primary coil of a transformer  815 , the secondary coil of which is formed by inductor L sec    816 . The inductor L sec    816  of the transformer  815  secondary is connected to a resonant circuit  817  formed by inductor L 2 , capacitor C 4    820 , capacitor C 2    822 , and capacitor C 3   825 . The transformer  815  up-converts the drive voltage (V d ) across the inductor L m    814  to the voltage that is applied to the output parallel resonant circuit  817 . The load voltage (V L ) is output by the parallel resonant circuit  817  and is applied to the load (represented by the load resistance R load    819  in  FIG. 22 ) corresponding to the impedance of the forceps&#39; jaws and any tissue or vessel gripped by the forceps  108 . As shown in  FIG. 15 , a pair of DC blocking capacitors C bl    840 - 1  and  840 - 2  is provided to prevent any DC signal being applied to the load  819 . 
     In one embodiment, the transformer  815  may be implemented with a Core Diameter (mm), Wire Diameter (mm), and Gap between secondary windings in accordance with the following specifications: 
     Core Diameter, D (mm)
 
 D= 19.9×10−3
 
     Wire diameter, W (mm) for 22 AWG wire
 
 W= 7.366×10−4
 
     Gap between secondary windings, in gap=0.125
 
 G =gap/25.4
 
     In this embodiment, the amount of electrical power supplied to the forceps  108  is controlled by varying the frequency of the switching signals used to switch the FETs  803 . This works because the resonant circuit  810  acts as a frequency dependent (loss less) attenuator. The closer the drive signal is to the resonant frequency of the resonant circuit  810 , the less the drive signal is attenuated. Similarly, as the frequency of the drive signal is moved away from the resonant frequency of the circuit  810 , the more the drive signal is attenuated and so the power supplied to the load reduces. In this embodiment, the frequency of the switching signals generated by the FET gate drive circuitry  805  is controlled by a controller  841  based on a desired power to be delivered to the load  819  and measurements of the load voltage (V L ) and of the load current (I L ) obtained by conventional voltage sensing circuitry  843  and current sensing circuitry  845 . The way that the controller  841  operates will be described in more detail below. 
     In one embodiment, the voltage sensing circuitry  843  and the current sensing circuitry  845  may be implemented with high bandwidth, high speed rail-to-rail amplifiers (e.g., LMH6643 by National Semiconductor). Such amplifiers, however, consume a relatively high current when they are operational. Accordingly, a power save circuit may be provided to reduce the supply voltage of the amplifiers when they are not being used in the voltage sensing circuitry  843  and the current sensing circuitry  845 . In one-embodiment, a step-down regulator (e.g., LT3502 by Linear Technologies) may be employed by the power save circuit to reduce the supply voltage of the rail-to-rail amplifiers and thus extend the life of the battery  300 . 
     In one embodiment, the transformer  815  and/or the inductor L s    812  may be implemented with a configuration of litz wire conductors to minimize the eddy-current effects in the windings of high-frequency inductive components. These effects include skin-effect losses and proximity effect losses. Both effects can be controlled by the use of litz wire, which are conductors made up of multiple individually insulated strands of wire twisted or woven together. Although the term litz wire is frequently reserved for conductors constructed according to a carefully prescribed pattern, in accordance with the present disclosure, any wire strands that are simply twisted or grouped together may be referred to as litz wire. Accordingly, as used herein, the term litz wire refers to any insulated twisted or grouped strands of wires. 
     By way of background, litz wire can reduce the severe eddy-current losses that otherwise limit the performance of high-frequency magnetic components, such as the transformer  815  and/or the inductor L s    812  used in the RF drive and control circuit  800  of  FIG. 22 . Although litz wire can be very expensive, certain design methodologies provide significant cost reduction without significant increases in loss, or more generally, enable the selection of a minimum loss design at any given cost. Losses in litz-wire transformer windings have been calculated by many authors, but relatively little work addresses the design problem of how to choose the number and diameter of strands for a particular application. Cost-constrained litz wire configurations are described in C. R. Sullivan, “Cost-Constrained Selection of Strand Wre and Number in a Litz-Wire Transformer Winding,”  IEEE Transactions on Power Electronics , vol. 16, no. 2, pp. 281-288, which is incorporated herein by reference. The choice of the degree of stranding in litz wire for a transformer winding is described in C. R. Sullivan, “Optimal Choice for Number of Strands in a Litz-Wire Transformer Winding,”  IEEE Transactions on Power Electronics , vol. 14, no. 2, pp. 283-291, which is incorporated herein by reference. 
     In one embodiment, the transformer  815  and/or the inductor L s    812  may be implemented with litz wire by HM Wire International, Inc., of Canton, Ohio or New England Wire Technologies of Lisbon, N.H., which has a slightly different construction in terms of the number of strands in the intermediate windings, but has the same total number of strands of either 44 gauge or 46 gauge wire by HM Wire International, Inc. Accordingly, the disclosure now turns to  FIGS. 23-35 , which illustrate one embodiment of the transformer  815  and the inductor L s    812  implemented with litz wire. 
       FIG. 23  illustrates a perspective view of one embodiment of the transformer  404  shown in  FIGS. 8 and 10  and shown as transformer  815  in connection with the RF drive circuit  800  illustrated in  FIG. 22 . As shown in  FIG. 23 , in one embodiment, the transformer  404  comprises a bobbin  804 , a ferrite core  806 , a primary coil  821  (e.g., inductor L m    814  in  FIG. 22 ), and a secondary coil  823  (e.g., inductor L sec    816  in  FIG. 22 ). In one embodiment, the bobbin  804  may be a 10-pin surface mounted device (SMD) provided by Ferroxcube International Holding B.V. In one embodiment, the ferrite core  806  may be an EFD 20/107 N49. In one embodiment, the transformer  815  has a power transfer of ˜45 W, a maximum secondary current of ˜1.5 A RMS, maximum secondary voltage of ˜90V RMS, maximum primary current of ˜15.5 A RMS, and a turns ratio of 20:2 (secondary turns:primary turns), for example. The operating frequency range of the transformer  404  is from ˜370 kHz to ˜550 kHz, and a preferred frequency of ˜430 kHz. It will be appreciated that these specification are provided as examples and should not be construed to be limiting of the scope of the appended claims. 
     In one embodiment, the transformer  404  comprises a ferrite core material having particular characteristics. The core used for both the inductor  406  and the transformer  404 , albeit with a different gap to yield the required A L  for each component. A L  has units of Henrys/turns 2 , so the inductance of a winding may be found by using NTURNS 2 *A L . In one embodiment, an A L  of 37 is used for the inductor  406 , and an A L  of 55 is used for the transformer  406 . This corresponds to a gap of approximately 0.8 mm and 2.0 mm respectively, although the A L  or the inductance is the parameter to which the manufacturing process controls, with the A L  being an intermediate quantity that we are not measuring directly. 
     In one embodiment, the inductance of the inductor  406  and transformer  404  winding may be measured directly with “golden bobbins,” which are squarely in the middle of the tolerance bands for the winding statistical distributions. Cores that are ground are then tested using the “golden bobbin” to assess whether the grind is good on the cores. Better results were yielded than the industry standard method, which is to fill a bobbin with as many windings as they can fit on the bobbin, and then back calculating the A L  of the core, and controlling A L  instead of the inductance. It was found that using a “golden bobbin” in the manufacturing process yielded better results. The bobbin is what the copper windings are secured to, and the ferrite E cores slip through a hole in the bobbin, and are secured with clips. 
       FIG. 24  illustrates a perspective view of one embodiment of the primary coil  821  (e.g., inductor L m    814  in  FIG. 22 ) of the transformer  404  illustrated in  FIG. 23 . In one embodiment, the primary coil  821  windings may be constructed using 300 strand/46 gauge litz wire as indicated in TABLE 1 below, among other suitable configurations. In one embodiment, primary coil  821  has an inductance of ˜270 nH, an AC resistance&lt;46 mΩ, and a DC resistance of ≤5 mΩ, for example. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Primary Coil 821 (L m  814) 
               
               
                 46 Gauge Litz Wire 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 300 Strands 46 AWG - 24 turns per foot (TPF) 
               
               
                   
                 Single Build MW80 155*C 
               
               
                   
                 Single Nylon Served 
               
               
                   
                 Construction: 5 × 3 × 20/46 AWG 
               
               
                   
                 Ft per lb: 412 Nominal 
               
               
                   
                 OD: 0.039″ Nominal 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 26  illustrates a bottom view of the primary coil  821  (e.g., inductor L m    814  in  FIG. 22 ) illustrated in  FIG. 24 .  FIG. 27  illustrates a side view of the primary coil  821  illustrated in  FIG. 24 .  FIG. 28  illustrates a sectional view of the primary coil  821  illustrated in  FIG. 24  taken along section  28 - 28 . 
       FIG. 25  illustrates a perspective view of one embodiment of a secondary coil  823  (e.g., inductor L sec    816  in  FIG. 22 ) of the transformer  404  illustrated in  FIG. 23 . In one embodiment, the secondary coil  823  windings may be constructed using 105 strand/44 gauge litz wire as indicated in TABLE 2 below, among other suitable configurations. In one embodiment, the secondary coil  823  has an inductance of 22 μH±5%@430 kHz, an AC resistance&lt;2.5Ω, and a DC resistance 80 mΩ, for example. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Secondary Coil 823 (L sec  816) 
               
               
                 44 Gauge Litz Wire 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   
                 105 Strands 44 AWG 24 TPF 
               
               
                   
                 Single Build MW80 155*C 
               
               
                   
                 Single Nylon Served 
               
               
                   
                 Construction: 5 × 21/44 AWG 
               
               
                   
                 Ft per lb: 1214 Nominal 
               
               
                   
                 OD: 0.023″ Nominal 
               
               
                   
                   
               
            
           
         
       
     
       FIG. 29  illustrates a bottom view of the secondary coil  823  (e.g., inductor L sec    816  in  FIG. 22 ) illustrated in  FIG. 25 .  FIG. 30  illustrates a side view of the secondary coil  823  illustrated in  FIG. 25 .  FIG. 31  illustrates a sectional view of the secondary coil  823  illustrated in  FIG. 30  taken along section  31 - 31 . 
       FIG. 32  is a perspective view of one embodiment of the inductor  406  shown in  FIGS. 8 and 10  and shown as inductor L s    812  in connection with the RF drive circuit  800  illustrated in  FIG. 22 . As shown in  FIG. 32 , in one embodiment, the inductor  406  comprises a bobbin  809 , a ferrite core  811 , and a coil  813 . In one embodiment, the bobbin  809  may be a 10-pin surface mounted device (SMD) provided by Ferroxcube International Holding B.V. In one embodiment, the ferrite core  811  may be an EFD 20/107 N49. In one embodiment, the coil  813  windings may be constructed using 300 strand/46 gauge litz wire wound at 24 TPF. In one embodiment, the inductor L s    812  may have an inductance of ˜345 nH±6%@430 kHz, an AC resistance&lt;50 mΩ, and a DC resistance 7 mΩ, for example. The operating frequency range of the inductor L s    812  is from ˜370 kHz to ˜550 kHz, and a preferred frequency of ˜430 kHz, and an operating current of ˜15.5 A rms. It will be appreciated that these specification are provided as examples and should not be construed to be limiting of the scope of the appended claims. 
       FIG. 33  illustrates a bottom view of the inductor  406  (e.g., inductor L s    812  in  FIG. 22 ) illustrated in  FIG. 32 .  FIG. 34  illustrates a side view of the inductor  406  illustrated in  FIG. 32 .  FIG. 35  illustrates a sectional view of the inductor  406  illustrated in  FIG. 34  taken along section  35 - 35 . 
     Accordingly, as described above in connection with  FIGS. 23-35 , in one embodiment, the transformer  404  (e.g., transformer  815 ) and/or the inductor  406  (e.g., inductor  812 ) used in the RF drive and control circuit  800  of  FIG. 22  may be implemented with litz wire. One litz wire configuration may be produced by twisting 21 strands of 44 AWG SPN wire at 18 twists per foot (left direction twisting). Another litz wire configuration may be produced by twisting 5×21/44 AWG (105/44 AWG SPN), also at 18 twists per foot (left direction twisting). Other litz wire configurations include 300/46 AWG litz wire as well as 46 AWG or finer gauge size wire. 
       FIG. 36  illustrates the main components of the controller  841 , according to one embodiment. In the embodiment illustrated in  FIG. 36 , the controller  841  is a microprocessor based controller and so most of the components illustrated in  FIG. 16  are software based components. Nevertheless, a hardware based controller  841  may be used instead. As shown, the controller  841  includes synchronous I, Q sampling circuitry  851  that receives the sensed voltage and current signals from the sensing circuitry  843  and  845  and obtains corresponding samples which are passed to a power, V rms  and I rms  calculation module  853 . The calculation module  853  uses the received samples to calculate the RMS voltage and RMS current applied to the load  819  ( FIG. 22 ; forceps  108  and tissue/vessel gripped thereby) and from them the power that is presently being supplied to the load  839 . The determined values are then passed to a frequency control module  855  and a medical device control module  857 . The medical device control module  857  uses the values to determine the present impedance of the load  819  and based on this determined impedance and a pre-defined algorithm, determines what set point power (P set ) should be applied to the frequency control module  855 . The medical device control module  857  is in turn controlled by signals received from a user input module  859  that receives inputs from the user (for example pressing buttons or activating the control levers  114 ,  110  on the handle  104 ) and also controls output devices (lights, a display, speaker or the like) on the handle  104  via a user output module  861 . 
     The frequency control module  855  uses the values obtained from the calculation module  853  and the power set point (P set ) obtained from the medical device control module  857  and predefined system limits (to be explained below), to determine whether or not to increase or decrease the applied frequency. The result of this decision is then passed to a square wave generation module  863  which, in this embodiment, increments or decrements the frequency of a square wave signal that it generates by 1 kHz, depending on the received decision. As those skilled in the art will appreciate, in an alternative embodiment, the frequency control module  855  may determine not only whether to increase or decrease the frequency, but also the amount of frequency change required. In this case, the square wave generation module  863  would generate the corresponding square wave signal with the desired frequency shift. In this embodiment, the square wave signal generated by the square wave generation module  863  is output to the FET gate drive circuitry  805 , which amplifies the signal and then applies it to the FET  803 - 1 . The FET gate drive circuitry  805  also inverts the signal applied to the FET  803 - 1  and applies the inverted signal to the FET  803 - 2 . 
       FIG. 37  is a signal plot illustrating the switching signals applied to the FETs  803 , a sinusoidal signal representing the measured current or voltage applied to the load  819 , and the timings when the synchronous sampling circuitry  851  samples the sensed load voltage and load current, according to one embodiment. In particular,  FIG. 37  shows the switching signal (labeled PWM 1  H) applied to upper FET  803 - 1  and the switching signal (labeled PWM 1  L) applied to lower FET  803 - 2 . Although not illustrated for simplicity, there is a dead time between PVVM 1 H and PVVM 1 L to ensure that that both FETs  803  are not on at the same time.  FIG. 17  also shows the measured load voltage/current (labeled OUTPUT). Both the load voltage and the load current will be a sinusoidal waveform, although they may be out of phase, depending on the impedance of the load  819 . As shown, the load current and load voltage are at the same drive frequency (f d ) as the switching Signals (PWM 1  H and PWM 1  L) used to switch the FETs  803 . Normally, when sampling a sinusoidal signal, it is necessary to sample the signal at a rate corresponding to at least twice the frequency of the signal being sampled—i.e. two samples per period. However, as the controller  841  knows the frequency of the switching signals, the synchronous sampling circuit  851  can sample the measured voltage/current signal at a lower rate. In this embodiment, the synchronous sampling circuit  851  samples the measured signal once per period, but at different phases in adjacent periods. In  FIG. 37 , this is illustrated by the “I” sample and the “Q” sample. The timing that the synchronous sampling circuit  51  makes these samples is controlled, in this embodiment, by the two control signals PWM 2  and PWM 3 , which have a fixed phase relative to the switching signals (PWM 1  H and PWM 1  L) and are out of phase with each other (preferably by quarter of the period as this makes the subsequent calculations easier). As shown, the synchronous sampling circuit  851  obtains an “I” sample on every other rising edge of the PWM 2  signal and the synchronous sampling circuit  851  obtains a “0” sample on every other rising edge of the PWM 3  signal. The synchronous sampling circuit  851  generates the PWM 2  and PWM 3  control signals from the square wave signal output by the square wave generator  863  (which is at the same frequency as the switching signals PWM 1  H and PWM 1  L). Thus control signals PWM 2  and PWM 3  also changes (whilst their relative phases stay the same). In this way, the sampling circuitry  851  continuously changes the timing at which it samples the sensed voltage and current signals as the frequency of the drive signal is changed so that the samples are always taken at the same time points within the period of the drive signal. Therefore, the sampling circuit  851  is performing a “synchronous” sampling operation instead of a more conventional sampling operation that just samples the input signal at a fixed sampling rate defined by a fixed sampling clock. 
     The samples obtained by the synchronous sampling circuitry  851  are then passed to the power, V rms  and I rms  calculation module  853  which can determine the magnitude and phase of the measured signal from just one “I” sample and one “Q” sample of the load current and load voltage. However, in this embodiment, to achieve some averaging, the calculation module  853  averages consecutive “I” samples to provide an average “I” value and consecutive “Q” samples to provide an average “0” value; and then uses the average I and Q values to determine the magnitude and phase of the measured signal (in a conventional manner). As those skilled in the art will appreciate, with a drive frequency of about 400 kHz and sampling once per period means that the synchronous sampling circuit  851  will have a sampling rate of 400 kHz and the calculation module  853  will produce a voltage measure and a current measure every 0.01 ms. The operation of the synchronous sampling circuit  851  offers an improvement over existing products, where measurements can not be made at the same rate and where only magnitude information is available (the phase information being lost). 
     In one embodiment, the RF amplifier and drive circuitry for the electrosurgical medical instrument  100  employs a resonant mode step-up switching regulator, running at the desired RF electrosurgical frequency to produce the required tissue effect. The waveform illustrated in  FIG. 18  can be employed to boost system efficiency and to relax the tolerances required on several custom components in the electronics system  400 . In one embodiment, a first generator control algorithm may be employed by a resonant mode switching topology to produce the high frequency, high voltage output signal necessary for the medical instrument  100 . The first generator control algorithm shifts the operating frequency of the resonant mode converter to be nearer or farther from the resonance point in order to control the voltage on the output of the device, which in turn controls the current and power on the output of the device. The drive waveform to the resonant mode converter has heretofore been a constant, fixed duty cycle, with frequency (and not amplitude) of the drive waveform being the only means of control. 
       FIG. 38  illustrates a drive waveform for driving the FET gate drive circuitry  805 , according to one embodiment. Accordingly, in another embodiment, a second generator control algorithm may be employed by a resonant mode switching topology to produce the high frequency, high voltage output signal necessary for the medical instrument  100 . The second generator control algorithm provides an additional means of control over the amplifier in order to reduce power output in order for the control system to track the power curve while maintaining the operational efficiency of the converter. As shown in  FIG. 38 , according to one embodiment, the second generator control algorithm is configured to not only modulate the drive frequency that the converter is operating at, but to also control the duty cycle of the drive waveform by duty cycle modulation. Accordingly, the drive waveform  890  illustrated in  FIG. 38  exhibits two degrees of freedom. Advantages of utilizing the drive waveform  890  modulation include flexibility, improved overall system efficiency, and reduced power dissipation and temperature rise in the amplifier&#39;s electronics and passive inductive components, as well as increased battery life due to increased system efficiency. 
       FIG. 39  illustrates a diagram of the digital processing system  900  located on the first substrate  408   a , according to one embodiment. The digital processing system  900  comprises a main processor  902 , a safety processor  904 , a controller  906 , a memory  908 , and a non-volatile memory  402 , among other components that are not shown for clarity of disclosure. The dual processor architecture comprises a first operation processor referred to as the main processor  902 , which is the primary processor for controlling the operation of the medical instrument  100 . In one aspect, the main processor  902  executes the software instructions to implement the controller  841  shown in  FIG. 22 . In one embodiment, the main processor  902  also may comprise an analog-to-digital (A/D) converter and pulse width modulators (PWM) for timing control. 
     The main processor  902  controls various functions of the overall medical instrument  100 . In one embodiment, the main processor receives voltage sense (V Sense) and current sense (I Sense) signals measured at the load (represented by the load resistance R load    819  in  FIG. 22 ) corresponding to the impedance of the forceps&#39; jaws and any tissue or vessel gripped by the forceps  108 . For example, the main processor  902  receives the V Sense and I Sense signals for the voltage sensing circuitry  843  and current sensing circuitry  845 , as shown in  FIG. 15 . The main processor  902  also receives tissue temperature (T sense) measurement at the load. Using the V Sense, I Sense, and T Sense, the processor  902  can execute a variety of algorithms to detect the state of the tissue based on impedance Z, where Z=V Sense/I Sense. In one embodiment, the medical instrument  100  is frequency agile from about 350 kHz to about 650 kHz. As previously discussed, the controller  841  changes the resonant operating frequency of the RF amplifier sections, controlling the pulse width modulation (PWM), reducing the output voltage (V) to the load, and enhancing the output current (I) to the load as described in connection with  FIGS. 22 and 36-38 , for example. 
     Examples of frequency agile algorithms that may be employed to operate the present surgical instrument  100  are described in the following commonly owned U.S. Patent Applications, each of which is incorporated herein by reference in its entirety: (1) U.S. patent application Ser. No. 12/896,351, entitled DEVICES AND TECHNIQUES FOR CUTTING AND COAGULATING TISSUE, now U.S. Pat. No. 9,089,360; (2) U.S. patent application Ser. No. 12/896,479, entitled SURGICAL GENERATOR FOR ULTRASONIC AND ELECTROSURGICAL DEVICES, now U.S. Pat. No. 8,956,349; (3) U.S. patent application Ser. No. 12/896,345, entitled SURGICAL GENERATOR FOR ULTRASONIC AND ELECTROSURGICAL DEVICES, now U.S. Pat. No. 8,986,302; (4) U.S. patent application Ser. No. 12/896,384, entitled SURGICAL GENERATOR FOR ULTRASONIC AND ELECTROSURGICAL DEVICES, now U.S. Pat. No. 8,951,248; (5) U.S. patent application Ser. No. 12/896,467, entitled SURGICAL GENERATOR FOR ULTRASONIC AND ELECTROSURGICAL DEVICES, now U.S. Pat. No. 9,050,093; (6) U.S. patent application Ser. No. 12/896,451, entitled SURGICAL GENERATOR FOR ULTRASONIC AND ELECTROSURGICAL DEVICES, now U.S. Pat. No. 9,039,695; (7) U.S. patent application Ser. No. 12/896,470, entitled SURGICAL GENERATOR FOR ULTRASONIC AND ELECTROSURGICAL DEVICES, now U.S. Pat. No. 9,060,776; and (8) U.S. patent application Ser. No. 12/503,775, entitled ULTRASONIC DEVICE FOR CUTTING AND COAGULATING WITH STEPPED OUTPUT, now U.S. Pat. No. 8,058,771. 
     In one embodiment, the main processor  902  also detects the limit switch end of stroke position (Lmt Sw Sense). The limit switch is activated when the knife reaches the end of stroke limit. The signal generated by the limit switch Lmt Sw Sense is provided to the main processor  902  to indicate the end-of-stroke condition of the knife. 
     In one embodiment, the main processor  902  also senses an actuation signal (Reed Sw Sense) associated with the magnetically operated element  606  located on the electronics system  400 . As previously described the magnetically operated element  606  is initially actuated when the initialization clip  600 ,  650  is removed. When the Reed Sw Sense is detected by the main processor  902 , an algorithm is executed to control the operation of the medical instrument  100 . One embodiment of such an algorithm is described in more detail hereinbelow. Further, on initial power up, when the magnetically operated element  606  connects the battery  300  supply to the electronics system  400 , a low resistance load is applied to the terminals of the battery  300  to check the internal resistance of the battery  300 . This enables the main processor  902  to determine the charge state of the battery  300  or in other words, determines the ability of the battery  300  to deliver power to the electronics system  400 . In one embodiment, the main processor  902  may simply determine the absolute value of the difference between the unloaded and loaded battery  300 . If the main processor  902  determines that the battery  300  does not have enough capacity to deliver a suitable amount of power, the main processor  902  disables the medical instrument  100  and outputs a Discharge Battery signal, as discussed in more detail hereinbelow, to controllably discharge the battery  300  such that it cannot be reused and is classified as an out-of-the box failure. 
     In one embodiment, as part of the algorithm, the main processor  902  enables one or more visual feedback elements  118 . As shown in  FIG. 39 , the visual feedback elements  118  comprise at least one red LED, at least one green LED, and at least one blue LED. Each of the LEDs are energized based on algorithms associated with the medical instrument  100 . The main processor  902  also actuates an audio feedback element  410  based on algorithm associated with the medical instrument  100 . In one embodiment, the audio feedback element  410  includes a piezoelectric buzzer operating at 65 dBa at 1 meter at a frequency between about 2.605 kHz to 2.800 kHz, for example. As previously discussed, the visual and audio feedback elements  118 ,  410  are not limited to the devices disclosed herein and are intended to encompass other visual and audio feedback elements. 
     In one embodiment, the main processor  902  executes battery shut-off and battery-drain/kill algorithms to shut-off the instrument  100  and/or drain the battery  300  under certain conditions described below. The algorithms monitor instrument usage and battery voltage and trigger shutdown of the instrument  100  and the drain the battery  300  in the event of unrecoverable faults or as a natural way to shutdown the instrument  100  and drain the battery  300 . 
     In one embodiment, an unrecoverable event triggers the medical instrument  100  to shutdown and drain the battery  330 . Events that can trigger the medical instrument  100  to shutdown and drain the battery  300  include, without limitation, (1) the detection of five consecutive firing short circuits; (2) activation of RF power when the activation button  114  is not pressed; (3) activation of RF power without activation of the audible feedback; (4) activation of the audible feedback without RF power; (5) the switch is stuck at power up for &gt;30 seconds; (6) the resting voltage of the battery  300  is less than 10.848V after any firing; and (7) three consecutive firings that are over or under the established load curve extremes of +/−20%. 
     In one embodiment, the medical instrument  100  may be shutdown and the battery  300  drained as a result natural usage of the instrument  100 , which includes, without limitation: (1) when the medical instrument  100  completes five firings after detecting a resting voltage of the battery  300  of 11.02V; (2) after the clip  600 ,  650  has been removed from the medical instrument  100 , if the instrument  100  has completed a real firing (more than three joules and the user gets the cycle complete tone 3) and if the user replaces the initialization clip  600 ,  650  on the instrument  100 , the instrument  100  will no longer be useable when they clip  600 ,  650  is once again removed from the instrument  100 ; (3) when the user depresses the disposal button  120  located on the bottom of the handle  104  of the instrument  100  for four seconds; (4) upon reaching a time limit: (a) after at least eight hours of use and if not used between hours six through eight, the instrument  100  it will shutdown; and (b) if used at least once between hours six and eight, the instrument  100  will extend the time limit to ten hours and then shutdown. 
     In one embodiment, the main processor  902  provides certain output signals. For example, one output signal is provided to the circuitry to discharge the battery  300  (Discharge Battery) signal. This is explained in more detail with reference to  FIG. 40 . There may be a need to discharge the battery  300  under several conditions according to algorithms associated with the medical instrument  100 . Such conditions and algorithm are discussed in more detail hereinbelow. In one embodiment, the battery  300  used to power the medical instrument  100  has an initial out of the box capacity ranging from about 6 to about 8 hours up to about 10 hours under certain circumstances. After a medical procedure, some capacity will remain in the battery  300 . Since the battery  300  is designed as a single use battery and is not rechargeable, the battery  300  is controllably discharged after use to prevent reuse of the medical instrument  100  when the battery  300  has a partial capacity. 
     In one embodiment, the main processor  902  can verify the output voltage (V) and current (I) sensing function by an artificial injection of voltage and current into the load. The main processor  902  then reads back the voltage and current from the load and determines whether the medical instrument  100  can operate or fail in safe mode. In one embodiment, the test voltage and current are applied to the dummy load via an electronically controlled switch. For example, the electronic switch may comprise a two-pole relay. The main processor  902  verifies the output sensing function once per hour when it is inactive and once prior to every firing. It will be appreciated that these periods may vary based on the particular implementation. To verify the output sensing function, the main processor  902  outputs inject test voltage (Inject Test V) and inject test current (Inject test I) signals to the output sensing test circuit described in connection with  FIG. 41  hereinbelow. As previously described, the main processor  902  reads the sensed voltage and current signals V Sense and I Sense to determine the operation of the voltage (V) and current (I) sensing function of the medical instrument  100 . 
     The main processor  902  is also coupled to a memory  908  and the nonvolatile memory  402 . The computer program instructions executed by the main processor  902  are stored in the nonvolatile memory  902  (e.g., EEPROM, FLASH memory, and the like). The memory  908 , which may be random access memory (RAM) may be used for storing instructions during execution, measured data, variables, among others. The memory  908  is volatile and its contents are erased when the battery  300  is discharged below a predetermine voltage level. The nonvolatile memory  402  is nonvolatile and its contents are not erased when the battery  300  is discharged below a predetermined level. In one embodiment, it may be desirable to erase the contents of the nonvolatile memory  402  to prevent its reuse, for example, when the medical instrument  100  has already been utilized in a procedure, the instrument  100  is determined to be an out-of-the box failure, or when the instrument  100  otherwise fails. In each of these circumstances, the main processor  902  initiates a battery  300  discharge operation. In such circumstances, program instructions in the nonvolatile memory  402  for erasing nonvolatile memory are transferred to the memory  908  where program execution resumes. The instructions executed from the memory  908  then erase the contents of the nonvolatile memory  402 . 
     The safety processor  904  is coupled to the main processor  902  and monitors the operation of the main processor  902 . If the safety processor  904  determines a malfunction of the main processor  902 , the safety processor  904  can disable the operation of the main processor  902  and shuts down the medical instrument  100  in a safe mode. 
     The controller  906  is coupled to both the main processor  902  and the safety processor  904 . In one embodiment, the controller  906  also monitors the operation of the main processor  902  and if the main processor  902  loses control, the controller  906  enables the safety processor to shut down the RF amplifier section in a safe manner. In one embodiment the controller  906  may be implemented as complex programmable logic device (CPLD), without limitation. 
     To preserve or extend the life of the battery  300 , the main processor  902 , the safety processor  904 , and/or the controller  906  may be powered down (e.g., placed in sleep mode) when they are not in use. This enables the digital processing system  900  to conserve energy to preserve or extend the life of the battery  300 . 
     In various embodiments, the main processor  902 , the safety processor  904 , or the controller  906  may comprise several separate functional elements, such as modules and/or blocks. Although certain modules and/or blocks may be described by way of example, it can be appreciated that a greater or lesser number of modules and/or blocks may be used and still fall within the scope of the embodiments. Further, although various embodiments may be described in terms of modules and/or blocks to facilitate description, such modules and/or blocks may be implemented by one or more than one hardware component, e.g., processor, Complex Programmable Logic Device (CPLD), Digital Signal Processor (DSP), Programmable Logic Devices (PLD), Application Specific Integrated Circuit (ASIC), circuits, registers and/or software components, e.g., programs, subroutines, logic and/or combinations of hardware and software components. 
     In one embodiment, the digital processing system  900  may comprise one or more embedded applications implemented as firmware, software, hardware, or any combination thereof. The digital processing system  900  may comprise various executable modules such as software, programs, data, drivers, application program interfaces (APIs), and so forth. The firmware may be stored in the nonvolatile memory  402  (NVM), such as in bit-masked read-only memory (ROM) or flash memory. In various implementations, storing the firmware in ROM may preserve flash memory. The NVM may comprise other types of memory including, for example, programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or battery backed random-access memory  908  (RAM) such as dynamic RAM (DRAM), Double-Data-Rate DRAM (DDRAM), and/or synchronous DRAM (SDRAM). 
       FIG. 40  illustrates a battery discharge circuit  1000 , according to one embodiment. Under normal operation line  1004  is held at a low potential and a current control device, such as a silicon controlled rectifier  1002 , is in the OFF state and the battery voltage V batt  is applied to the electronics system  400  since no current flows from the anode “A” to the cathode “C” of the silicon controlled rectifier  1002 . When, a high potential control signal “Discharge Battery” is applied by the main processor  902  on line  1004 , the gate “G” of the silicon controlled rectifier  1002  is held high by capacitor C 1  and the silicon controlled rectifier  1002  conducts current from the anode “A” to the “C.” The discharge current is limited by resistor R 4 . In alternate embodiments, rather then using the silicon controlled rectifier  1002 , the current control device may be implemented using one or more diodes, transistors (e.g., FET, bipolar, unipolar), relays (solid state or electromechanical), optical isolators, optical couplers, among other electronic elements that can be configured to for an electronic switch to control the discharge of current from the battery  300 . 
       FIG. 41  illustrates a RF amplifier section with an output sensing test circuit and magnetic switch element, according to one embodiment. As previously discussed, in one embodiment, the main processor  902  can verify the output current (I) and output voltage (V) sensing function by injecting a corresponding first test current  1102  and second test current  1104  into a dummy load  1114 . The main processor  902  then reads back the corresponding output sense current (I Out Sense  1 ) through current sense terminal  1120  and output sense current (I Out Sense  2 ) through voltage sense terminal  1122  from the dummy load  1114  and determines whether the medical instrument  100  can operate or fail in safe mode. In one embodiment, the test current and voltage are applied to the dummy load via electronically controlled switches such as FET transistors, solid state relay, two-pole relay, and the like. The main processor  902  verifies the output sensing functions once per hour when it is inactive and once prior to every firing. It will be appreciated that these periods may vary based on the particular implementation. 
     To verify the output sensing function, the main processor  902  disables the operation of the RF amplifier section  1112  by disabling the driver circuit  1116 . Once the RF amplifier section  1112  is disabled, the main processor  902  outputs a first inject test current (Inject Test I) signal and a second inject test voltage (Inject Test V) signal to the output sensing test circuit  1100 . As a result a first test current  1102  is injected into resistors that turn ON transistor T 1   1106 , which turns ON transistor T 2   1108  to generate I Out Sense  1  current through the transistor T 2   1108 . The current I Out Sense  1  flows out of the current sense terminal  1120  and is detected by the main processor  902  as the I Sense signal. A second test current  1104  is applied through the input section of a solid state relay  1110  (SSR). This causes a current I Out Sense  2  to flow through the dummy load  1114 . The current I Out Sense  2  flows out of the current sense terminal  1122  and is detected by the main processor  902  as the V Sense signal. The dummy load  1114  load comprises a first voltage divider network comprised of resistors R 1 -R 4  and a second voltage divider network comprised of R 5 -R 8 . As previously described, the main processor  902  reads the sensed voltage and current signals V Sense and I Sense to determine the operation of the voltage (V) and current (I) sensing function of the medical instrument  100 . 
     In one embodiment, the magnetically actuated element  606 , which works in conjunction with the magnet  602  located in the clip  600 ,  650 . As shown in  FIG. 41 , in one embodiment, the magnetically operated element  606  may be implemented as a reed switch  1118 . The reed switch  1118  electrically disconnects the battery power from the electronics system  400  while it is held in a first state by the magnetic flux generated by the magnet  602 . When the magnet  602  is removed and the magnetic flux does not influence the reed switch  1118 , battery power is connected to the electronics system  400  and the system undergoes an initialization algorithm, as described hereinbelow. 
     Before the describing the initialization algorithm, several connection options for the battery  300  are now described with reference to  FIGS. 42-47 . As previously discussed, the electronics system  400  will not be powered when undergoing sterilization, and will draw no current. In one embodiment, the electronics system  400  is disabled by a magnetically operated element located in the clip  600 ,  650 , one example of which is the reed switch  1118  shown in  FIG. 41 , and the magnet  602  which is encased in the clip  600  and the tilted magnetic pocket  654  of the clip  650 . The clip  600 ,  650  is fitted to the medical instrument  100  as part of the manufacturing process, and must be removed to enable power from the battery  300 . When powered, in the idle condition the load circuit draws an average of about 10 mA, with peaks of up to about 65 mA. When the activation button  114  is pressed, the device draws an average of about 5 A, with peaks of about 15.5 A from the battery  300 . When packaged, the jaws are closed and there is no material between them. The voltage generated across the jaws is about 85V rms. This arrangement means there are two methods for preventing the generation of high voltages or currents—the magnetic clip  600 ,  650  is the primary disabling mechanism, and the activation button  114  is the second. 
     As previously discussed, certain sections of the hardware circuits may be shut down or placed in sleep mode to conserve energy and thus extend the life of the battery  300 . In particular, amplifier circuits associated with the injection of the test current and test voltage and sensing the output sense currents may be placed in sleep mode or periodically shut down to conserve energy. 
       FIG. 42  illustrates a fused battery connected to a substrate-mounted field effect transistor (FET), according to one embodiment. In the embodiment shown in  FIG. 42 , a battery connection circuit  1200  comprises the battery  300 , the magnet  602 , the reed switch  1118 , an FET  1202 , two resistors R 1 , R 2   1204 ,  1206 , and the electronics system  400 . In this implementation, when the protective clip  600  is removed, the reed switch  1118  closes, enabling current to flow through the control FET  1202 , thus coupling the electronics system  400  to the return (−) terminal of the battery  300 . Leakage current through the FET is approximately 1 uA. The battery is coupled to the (+) and (−) terminals via corresponding fuses  1208 ,  1210 . 
       FIG. 43  illustrates a fused battery connected to a substrate-mounted control relay, according to one embodiment. In the embodiment shown in  FIG. 43 , a battery connection circuit  1300  comprises the battery  300 , the magnet  602 , the reed switch  1118 , and a control relay  1302  comprising a primary winding  1304  that controls a switch  1306 . In this implementation, when the protective clip  600  is removed, the reed switch  1118  closes, energizing the relay  1302  and connecting the electronics system  400  to the return (−) terminal of the battery  300 . Leakage current is zero, because the switch  1306  is physically open when the primary winding  1304  in not energized. The operating current, however, to hold the relay  1304  open is approximately 5 mA, which could involve increasing battery size. 
       FIG. 44  illustrates a potted fused battery connected to a substrate-mounted FET, according to one embodiment. The connection circuit  1400  is similar to the connection circuit  1200  shown in  FIG. 42 , but with the top of the battery  300  potted in potting compound  1402 . Thus, EtO sterilization gas will have no access to the individual battery cells  300   a ,  300   b ,  300   c , and the first exposed contact is to the fused contacts. 
       FIG. 45  illustrates a potted fused battery connected to a substrate-mounted control relay, according to one embodiment. The connection circuit  1500  is similar to the connection circuit  1300  shown in  FIG. 23 , but with the top of the battery  300  potted in potting compound  1402 . Thus, EtO sterilization gas will have no access to the individual battery cells  300   a ,  300   b ,  300   c , and the first exposed contact is to the fused contacts. 
       FIG. 46  illustrates a potted fused battery including a reed relay and control FET, according to one embodiment. The connection circuit  1600  is similar to the connection circuit  1400  shown in  FIG. 24 , but with reed relay  1118  and the control FET  1202  included in the potting compound  1402  as well as the top of the battery  300 . Thus, EtO sterilization gas will have no access to the individual battery cells  300   a ,  300   b ,  300   c , the reed relay  1118 , and the control FET  1202 , and the first exposed contact is to the fused contacts. 
       FIG. 47  illustrates a potted fused battery including a reed relay and control relay, according to one embodiment. The connection circuit  1700  is similar to the connection circuit  1500  shown in  FIG. 45 , but with reed relay  1118  and the control relay  1302  included in the potting compound  1402  as well as the top of the battery  300 . Thus, EtO sterilization gas will have no access to the individual battery cells  300   a ,  300   b ,  300   c , the reed relay  1118 , and the control relay  1302 , and the first exposed contact is to the fused contacts. 
     Having described various systems associated with the medical instrument  100 , the description now turns to a user interface specification of the medical instrument  100 , according to one embodiment. Accordingly, in one embodiment, the medical instrument  100  comprises visual feedback elements  118   a ,  118   b . In one embodiment, the visual feedback elements  118   a ,  118   b  each comprises RED, GREEN, BLUE (RGB) LEDs as shown in  FIG. 39 . 
     The state of the medical instrument  100  can be determined by the state of the visual feedback elements  118   a ,  118   b  as follows: 
     Solid Green: indicates that the medical instrument  100  is ready to be used, everything is functioning normally. 
     Flashing Green: indicates that medical instrument  100  is ready to be used, but there is only enough energy for a limited, e.g., low, number of operations such as transections remaining (a minimum of 5 transections are left when flashing first begins). In one embodiment, the rate of flashing is 300 ms on, 300 ms off, 300 ms on, 300 ms off. 
     Solid Blue: indicates that energy is being delivered to the medical instrument  100 . 
     Solid Red: indicates a terminal failure and the medical instrument  100  can no longer be used. Energy is not being delivered to the medical instrument  100 . All Solid Red light conditions have a 4 second timeout; after which the LED goes OFF. Power cannot be activated when the LED is Solid Red—can only activate power when LED is Green or Flashing Green. 
     Flashing Red: indicates a fault that may be recoverable and to wait for the light to change to Green or Red before operation can be resumed. Energy is not being delivered to the medical instrument  100  when the LED is Flashing Red. The rate of flashing is 300 ms on, 300 ms off, 300 ms on, 300 ms off. Power cannot be activated when the LED is Flashing Red—can only activate power when the LED Is Green or Flashing Green. 
     OFF: If before the plastic clip  600  has been removed, indicates that device has not yet been powered ON by removing the clip  600 . If any time after the clip  600  has been removed, indicates that device is permanently powered OFF, and can be disposed of. 
     In one embodiment, the medical instrument  100  comprises an audio feedback element  410 . The state of the medical instrument  100  can be determined by the state of the audio feedback element  410  as follows: 
     Power ON Tone: indicates that the medical instrument  100  has been powered ON. This occurs when the plastic clip  600  is removed. The audio feedback element  410  emits an audible 2.55 kHz 800 ms beep. 
     Activation Tone: indicates that energy is being delivered. This occurs when the hand activation button  114  is pressed by the user. The audio feedback element  410  emits an audible 2.55 kHz 150 ms beep, 200 ms pause, 2.55 kHz 150 ms beep, 200 ms pause, an so on. The beeping pattern continues as long as power is being activated and upper impedance limit has not been reached. 
     Activation Tone2: indicates that the upper impedance threshold has been reached. This occurs when the hand activation button  114  is pressed by user, and the upper impedance limit has been reached. The audio feedback element  410  emits an audible 2.8 kHz 150 ms beep, 200 ms pause, 2.8 kHz 150 ms beep, 200 ms pause, and so on. The Tone2 beeping pattern latches. After it has been reached, it continues as long as power is being activated or until Cycle Complete. 
     Cycle Complete Tone: indicates that the activation cycle is complete. The audio feedback element  410  emits an audible 2.8 kHz 800 ms beep. 
     Alert Tone: indicates an alert. The LED visual feedback element  118   a ,  118   b  provides further information. The audio feedback element  410  emits an audible 2.9 kHz 250 ms beep, 50 ms pause, 2.55 kHz 350 ms beep, 200 ms pause, 2.9 kHz 250 ms beep, 50 ms pause 2.55 kHz 350 ms beep, 200 ms pause, 2.9 kHz 250 ms beep, 50 ms pause, 2.55 kHz 350 ms beep. The two-tone beep repeats three times, then does not repeat after that). Power to the medical instrument  100  cannot be activated until “alert” sound has completed. 
     Timeout: indicates that activation cycle has timed out. Reactivate to continue. The audio feedback element  410  emits an audible 2.8 kHz 50 ms beep, 50 ms pause, 2.8 kHz 50 ms beep. 
     Solid Tone: indicates that the user disable button is being pressed. The audio feedback element  410  emits an audible continuous 2.55 kHz tone while being held, up to 4 seconds. 
     TABLE 3 below summarizes one embodiment of a user interface indicating the status (e.g., event/scenario) of the medical instrument  100  and the corresponding visual and audible feedback provided by the user interface. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Device Status 
                 LED Feedback 
                 Audible Feedback 
                 Notes 
               
               
                   
               
             
            
               
                 Power is OFF 
                 No light 
                 None 
                   
               
               
                 Turn power ON by 
                 Solid Green 
                 One long beep 
               
               
                 removing the 
                 Illuminates immediately when 
                 immediately when 
               
               
                 initialization Clip. 
                 initialization Clip is removed. 
                 initialization Clip is 
               
               
                   
                 Indicates device is ready to be used, 
                 removed indicates 
               
               
                   
                 everything functioning normally. 
                 power in ON. 
               
               
                 Power is ON but not 
                 Solid Green 
                 None 
               
               
                 being activated, 
                 Device ready to be used, everything 
               
               
                 device ready, above 
                 functioning normally. 
               
               
                 the “low transections 
               
               
                 remaining” 
               
               
                 threshold. 
               
               
                 Power ON, device 
                 Flashing Green 
                 Two tone beeps: 
               
               
                 ready, power not 
                 Indicates that device is ready to be 
                 Indicates an alert: 
               
               
                 being activated, 
                 used, but a low number of 
                 look at LED 
               
               
                 below the “low 
                 transections remain; a minimum of 
                 indicators for 
               
               
                 transections 
                 five transections are left when 
                 further information. 
               
               
                 remaining” 
                 flashing first begins. 
               
               
                 threshold. 
               
               
                 Power ON, device 
                 Solid Red 
                 Two tone beeps: 
               
               
                 ready, power not 
                 Indicates a terminal failure, device 
                 Indicates an alert: 
               
               
                 being activated, “No 
                 can no longer be used. Energy is 
                 look at LED 
               
               
                 transections 
                 not being delivered. 
                 indicators for 
               
               
                 remaining” 
                   
                 further information. 
               
               
                 Activating power 
                 Solid Blue 
                 Continuous 
                 Feedback for 
               
               
                   
                 Energy is being delivered. 
                 beeping during 
                 activation power is 
               
               
                   
                   
                 power activation. 
                 not affected by the 
               
               
                   
                   
                 Indicates energy is 
                 ‘low transections 
               
               
                   
                   
                 being delivered. 
                 remaining’ 
               
               
                   
                   
                   
                 threshold- 
               
               
                   
                   
                   
                 behaves the same 
               
               
                   
                   
                   
                 whether above or 
               
               
                   
                   
                   
                 below threshold 
               
               
                 Activation cycle 
                 Solid Blue until two short beep 
                 Two short beeps. 
                 Upon detection of 
               
               
                 timeout occurs after 
                 sound completes, then changes to 
                 Indicates that the 
                 timeout, activation 
               
               
                 25 sec of power 
                 Solid Green. Indicates device is 
                 activation cycle 
                 beeping will be 
               
               
                 activation without 
                 ready to be used, everything 
                 has timed out. 
                 immediately 
               
               
                 reaching Cycle 
                 functioning normally. 
                 Reactivate to 
                 interrupted. After 
               
               
                 Complete. 
                   
                 continue. 
                 the interruption of 
               
               
                   
                   
                   
                 activation beeping 
               
               
                   
                   
                   
                 there will be a 
               
               
                   
                   
                   
                 100 ms pause. 
               
               
                   
                   
                   
                 After the 100 ms 
               
               
                   
                   
                   
                 pause, there will 
               
               
                   
                   
                   
                 be the “Timeout” 
               
               
                   
                   
                   
                 audio feedback. 
               
               
                 Cycle Complete 
                 Solid Blue until Cycle Complete 
                 One long beep. 
                 Cycle complete 
               
               
                   
                 sound finishes, then changes to 
                 Indicates that 
                 sound should 
               
               
                   
                 Solid Green. 
                 activation cycle 
                 occur after the first 
               
               
                   
                   
                 is complete. 
                 (200 ms) activation 
               
               
                   
                   
                   
                 beeping pause 
               
               
                   
                   
                   
                 following system 
               
               
                   
                   
                   
                 detection of cycle 
               
               
                   
                   
                   
                 complete. 
               
               
                 Short Detected 
                 Flashing Red, while in short circuit 
                 Two tone beeps. 
                 There will be a 
               
               
                   
                 mode. LED returns to Solid Green 
                 Indicates an alert: 
                 “five strikes and 
               
               
                   
                 when short circuit mode is cleared, 
                 look at LED 
                 out’ approach to 
               
               
                   
                 or goes to Solid Red if terminal 
                 indicators for 
                 this condition: if a 
               
               
                   
                 failure. 
                 further information. 
                 short is detected 
               
               
                   
                 Flashing Red indicates a fault that 
                   
                 on five 
               
               
                   
                 may be recoverable: wait for LED to 
                   
                 consecutive 
               
               
                   
                 change to Green or Red. 
                   
                 activations, the 
               
               
                   
                 Energy is not being detected when 
                   
                 fifth detection will 
               
               
                   
                 LED is Flashing Red. 
                   
                 result in a terminal 
               
               
                   
                   
                   
                 system failure. 
               
               
                   
                   
                   
                 Upon detection of 
               
               
                   
                   
                   
                 short, the 
               
               
                   
                   
                   
                 activation beeping 
               
               
                   
                   
                   
                 will be immediately 
               
               
                   
                   
                   
                 interrupted. After 
               
               
                   
                   
                   
                 the interruption of 
               
               
                   
                   
                   
                 activation beeping 
               
               
                   
                   
                   
                 there will be a 
               
               
                   
                   
                   
                 100 ms pause. 
               
               
                   
                   
                   
                 After the 100 ms 
               
               
                   
                   
                   
                 pause, there will 
               
               
                   
                   
                   
                 be the “Alert” 
               
               
                   
                   
                   
                 audio feedback. 
               
               
                 Over-temperature 
                 Flashing Red, while in over- 
                 Two tone beeps. 
                 Upon detection of 
               
               
                 condition 
                 temperature condition. 
                 Indicates an alert: 
                 a temporary over- 
               
               
                   
                 LED returns to Solid Green when 
                 look at LED 
                 temperature 
               
               
                   
                 temperature drops below threshold. 
                 indicator for 
                 condition during 
               
               
                   
                 Flashing Red indicates a fault that 
                 further information. 
                 activation, 
               
               
                   
                 may be recoverable: wait for LED to 
                   
                 activation/ 
               
               
                   
                 change to Green or Red. 
                   
                 beeping will not be 
               
               
                   
                 Energy is not being delivered when 
                   
                 interrupted. After 
               
               
                   
                 LED is Flashing Red. 
                   
                 the activation/ 
               
               
                   
                   
                   
                 beeping has been 
               
               
                   
                   
                   
                 completed, there 
               
               
                   
                   
                   
                 will be a 100 ms 
               
               
                   
                   
                   
                 pause. After the 
               
               
                   
                   
                   
                 100 ms pause, 
               
               
                   
                   
                   
                 there will be the 
               
               
                   
                   
                   
                 ‘Alert’ audio 
               
               
                   
                   
                   
                 feedback. 
               
               
                 Terminal System 
                 Solid Red 
                 Two tone beeps. 
                 Upon detection of 
               
               
                 failure 
                 LED red light stays on for four 
                 Indicates an alert: 
                 terminal system 
               
               
                   
                 seconds and then goes off. 
                 look at LED 
                 failure, any 
               
               
                   
                 Indicates a terminal failure, device 
                 indicator for 
                 activation beeping 
               
               
                   
                 can no longer be used. 
                 further information. 
                 (if applicable) will 
               
               
                   
                 Energy is not being delivered when 
                   
                 be immediately 
               
               
                   
                 LED is Solid Red. 
                   
                 interrupted. After 
               
               
                   
                   
                   
                 the interruption of 
               
               
                   
                   
                   
                 any activation 
               
               
                   
                   
                   
                 beeping there will 
               
               
                   
                   
                   
                 be a 100 ms 
               
               
                   
                   
                   
                 pause. After the 
               
               
                   
                   
                   
                 100 ms pause, 
               
               
                   
                   
                   
                 there will be the 
               
               
                   
                   
                   
                 ‘Alert’ audio 
               
               
                   
                   
                   
                 feedback. 
               
               
                   
                   
                   
                 All Solid Red light 
               
               
                   
                   
                   
                 conditions have a 
               
               
                   
                   
                   
                 4 second timeout, 
               
               
                   
                   
                   
                 after which the 
               
               
                   
                   
                   
                 LED goes OFF 
               
               
                 User initiates device 
                 While User Disable Button is 
                 Solid continuous 
               
               
                 disabling before 
                 pressed and held continuously up to 
                 tone while 
               
               
                 disposal. Note: 
                 four seconds, LED is Flashing Red. 
                 pressing and 
               
               
                 User can disable the 
                 After four continuous seconds of 
                 holding User 
               
               
                 device by pressing 
                 User Disable Button being held, 
                 Disable Button 
               
               
                 and holding User 
                 LED goes to Solid Red. 
                 continuously up to 
               
               
                 Disable Button on 
                 NOTE: LED red light stays on four 
                 four seconds. 
               
               
                 bottom of handle for 
                 seconds and then goes off. 
                 After four 
               
               
                 four continuous 
                 Indicates a terminal failure, and 
                 continuous 
               
               
                 seconds. 
                 device can no longer be used. 
                 seconds of 
               
               
                   
                 Energy is not being delivered. 
                 pressing User 
               
               
                   
                 If User Disable Button is released at 
                 Disable Button, 
               
               
                   
                 any time before four continuous 
                 sound changes to 
               
               
                   
                 seconds have passed, LED will 
                 two tone beeps. 
               
               
                   
                 return to Solid Green or Flashing 
                 Indicates an alert: 
               
               
                   
                 Green as appropriate. 
                 look at LED 
               
               
                   
                   
                 indicators for 
               
               
                   
                   
                 further information. 
               
               
                   
               
            
           
         
       
     
     TABLE 4 below summarizes an additional or alternative embodiment of the status (e.g., event/scenario) of the medical instrument  100  and the corresponding visual and audible feedback provided by the user interface. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                 Device Status 
                 LED Feedback 
                 Audible Feedback 
                 Notes 
               
               
                   
               
             
            
               
                 Power is OFF 
                 No light 
                 None 
                   
               
               
                 Incomplete Cycle: 
                 Solid Blue, until activation button is 
                 None 
               
               
                 user releases 
                 released, then Solid Green 
               
               
                 activation button 
               
               
                 prior to cycle 
               
               
                 complete and before 
               
               
                 the 15 second 
               
               
                 activation timeout. 
               
               
                 Power ON, ready, 
                 Flashing Green 
                 Alert Tone 
                 After the 
               
               
                 power not being 
                   
                   
                 appearance of the 
               
               
                 activated, below the 
                   
                   
                 Green Flashing 
               
               
                 Low Transections 
                   
                   
                 LED, there will be 
               
               
                 Remaining 
                   
                   
                 5 transections 
               
               
                 threshold. 
                   
                   
                 remaining. Ad 
               
               
                   
                   
                   
                 If an activation 
               
               
                   
                   
                   
                 ends with a 
               
               
                   
                   
                   
                 detection of an 
               
               
                   
                   
                   
                 activation timeout, 
               
               
                   
                   
                   
                 short detection, or 
               
               
                   
                   
                   
                 over-temperature 
               
               
                   
                   
                   
                 detection-and- 
               
               
                   
                   
                   
                 the system has 
               
               
                   
                   
                   
                 also crossed the 
               
               
                   
                   
                   
                 low-uses 
               
               
                   
                   
                   
                 remaining 
               
               
                   
                   
                   
                 threshold after the 
               
               
                   
                   
                   
                 same activation- 
               
               
                   
                   
                   
                 then-the ‘Alert’ 
               
               
                   
                   
                   
                 would sound once 
               
               
                   
                   
                   
                 (as opposed to 
               
               
                   
                   
                   
                 twice, or multiple 
               
               
                   
                   
                   
                 times). 
               
               
                   
                   
                   
                 In terms of alert 
               
               
                   
                   
                   
                 hierarchy in this 
               
               
                   
                   
                   
                 scenario in regard 
               
               
                   
                   
                   
                 to the LED 
               
               
                   
                   
                   
                 behavior, a short 
               
               
                   
                   
                   
                 detection or over 
               
               
                   
                   
                   
                 temperature takes 
               
               
                   
                   
                   
                 precedence over 
               
               
                   
                   
                   
                 the low-uses 
               
               
                   
                   
                   
                 remaining indicator 
               
               
                   
                   
                   
                 Once either the 
               
               
                   
                   
                   
                 short or over- 
               
               
                   
                   
                   
                 temperature 
               
               
                   
                   
                   
                 condition is 
               
               
                   
                   
                   
                 cleared by the 
               
               
                   
                   
                   
                 system, the LED 
               
               
                   
                   
                   
                 would then go to 
               
               
                   
                   
                   
                 Flashing Green to 
               
               
                   
                   
                   
                 indicate the device 
               
               
                   
                   
                   
                 is ready to be 
               
               
                   
                   
                   
                 used, but there are 
               
               
                   
                   
                   
                 a low number of 
               
               
                   
                   
                   
                 transections 
               
               
                   
                   
                   
                 remaining. 
               
               
                 power ON, ready, 
                 Solid Red 
                 Alert Tone 
                 All Solid Red light 
               
               
                 power not being 
                   
                   
                 conditions have a 
               
               
                 activated, No 
                   
                   
                 4 second timeout, 
               
               
                 Transections 
                   
                   
                 after which the 
               
               
                 Remaining. 
                   
                   
                 LED goes OFF. 
               
               
                 User Disables 
                 Flashing Red while pressing &amp; 
                 Solid Tone 
                 User can disable 
               
               
                 Device before 
                 holding user disable button 120 
                 Alert Tone 
                 the device by 
               
               
                 disposal 
                 continuously up to 4 seconds. After 
                   
                 pressing &amp; holding 
               
               
                   
                 four continuous seconds of pressing 
                   
                 the user disable 
               
               
                   
                 user disable button, the LED goes to 
                   
                 button on the 
               
               
                   
                 Solid Red, then the LED goes OFF 
                   
                 bottom of the 
               
               
                   
                 after 4 seconds timeout. If user 
                   
                 handle for 4 
               
               
                   
                 releases user disable button at any 
                   
                 continuous 
               
               
                   
                 time before 4 continuous seconds, 
                   
                 seconds. 
               
               
                   
                 the LED will return to Solid Green 
                   
                 The “Solid Tone” 
               
               
                   
                   
                   
                 audio feedback is 
               
               
                   
                   
                   
                 a solid continuous 
               
               
                   
                   
                   
                 tone that occurs as 
               
               
                   
                   
                   
                 long as user 
               
               
                   
                   
                   
                 presses &amp; holds 
               
               
                   
                   
                   
                 user disable 
               
               
                   
                   
                   
                 button, up to 4 
               
               
                   
                   
                   
                 seconds. If user 
               
               
                   
                   
                   
                 releases user 
               
               
                   
                   
                   
                 disable button at 
               
               
                   
                   
                   
                 any time before 4 
               
               
                   
                   
                   
                 continuous 
               
               
                   
                   
                   
                 seconds, sound 
               
               
                   
                   
                   
                 goes off. At the 
               
               
                   
                   
                   
                 end of 4 seconds 
               
               
                   
                   
                   
                 of continuous 
               
               
                   
                   
                   
                 pressing, the 
               
               
                   
                   
                   
                 “Solid Tone” 
               
               
                   
                   
                   
                 stops, followed by 
               
               
                   
                   
                   
                 a 100 ms pause, 
               
               
                   
                   
                   
                 followed by the 
               
               
                   
                   
                   
                 “Alert” audio 
               
               
                   
                   
                   
                 feedback. The 
               
               
                   
                   
                   
                 “Alert” audio 
               
               
                   
                   
                   
                 feedback is 
               
               
                   
                   
                   
                 accompanied by 
               
               
                   
                   
                   
                 the LED changing 
               
               
                   
                   
                   
                 to Solid Red, then 
               
               
                   
                   
                   
                 LED goes OFF 
               
               
                   
                   
                   
                 after 4 second 
               
               
                   
                   
                   
                 timeout. 
               
               
                 Activating Power - 
                 Solid Blue 
                 Activation Tone2 
                 Tone2 indicates 
               
               
                 Tone 2 
                   
                   
                 that the upper 
               
               
                   
                   
                   
                 impedance limit 
               
               
                   
                   
                   
                 has been reached 
               
               
                   
                   
                   
                 during activation, 
               
               
                   
                   
                   
                 and that the knife 
               
               
                   
                   
                   
                 is ready to be fully 
               
               
                   
                   
                   
                 advanced. 
               
               
                   
               
            
           
         
       
     
       FIGS. 48A and 48B  is a flow diagram of a process  1800  for initializing the medical instrument  100  fitted with the initialization clip  600 ,  650 , according to one embodiment. As shown in the process  1800 , at  1802  the medical instrument  100  is programmed with an application code. The application code is a set of computer instructions stored in the nonvolatile memory  402  that may be executed by the main processor  902 , the safety processor  904 , the controller  906 , or any combination thereof. The Production Test Complete flag is set to FALSE and the Device Used flag also is set to FALSE. 
     The instrument  100  is then fitted with the clip  600 ,  650  and is turned OFF at  1804  and the instrument  100  enters what is referred to as the “assembly state.” The Production Test Complete flag remains set to FALSE and the Device Used flag also remains set to FALSE. 
     At  1806  the instrument  100  is placed in the production mode after the clip  600 ,  650  is removed. In the production mode, the BLUE and GREEN LEDs  118   a, b  are turned ON and activation is inhibited. The Production Test Complete flag remains set to FALSE and the Device Used flag also remains set to FALSE. A timeout counter is started. 
     After a 1 second timeout, at  1808  the instrument  100  is still in the production mode, but remains idle. The user interface operates as per normal mode. From the production mode  1808  the process can continue to  1804  or to  1810 . If the clip  600 ,  650  is fitted on the instrument  100  prior to a ten minute timeout, the process  1800  returns to  1804  were the instrument  100  is turned OFF and is placed in the assembly state. After a ten minute timeout period, the process  1800  continues at  1810 . The instrument  100  is still in the production mode, but in a low power consumption state. The BLUE and GREEN LEDs  118   a, b  are intermittently ON (0.1 s ON and 1.9 s OFF). The clip  600 ,  650  is fitted back on the instrument  100 , which turns the instrument  100  OFF, and the process  1800  returns to  1804 . If at  1808  the instrument  100  is activated before the clip  600  is restored or before the ten-minute timeout period, the process continues to test mode at  1812 . The Production Test Complete flag remains set to FALSE and the Device Used flag also remains set to FALSE. In test mode activations may be limited to four and timeout may be set to ten minutes. Furthermore, upon entry to test mode, the GREEN and BLUE LEDs  118   a, b  are illuminated for 1 s. Subsequently, the LEDs  118   a, b  and the audio feedback element  410  follow the user interface specification. 
     At  1812 , the instrument  100  is placed in test mode where the RF amplifier subsection  800  is turned ON. The user interface operates per normal mode. The Production Test Complete flag is set to TRUE and the Device Used flag remains set to FALSE. 
     From  1812 , the clip  600 ,  650  may be fitted to the instrument  100  turning the instrument  100  OFF and the process  1800  may continue at  1818  where the instrument  100  is placed in a shipping state. The Production Test Complete flag remains set to TRUE and the Device Used flag remains set to FALSE. 
     From  1812 , the process may continue at  1814  after the instrument  100  is de-activated for the first three times. At  1814  the instrument  100  is placed in idle mode. The UI operates as pre normal. The Production Test Complete flag remains set to TRUE and the Device Used flag remains set to FALSE. The instrument  100  is activated once more and the process  1800  continues to  1812 . The instrument  100  is de-activated a fourth time, the clip  600 ,  650  is fitted to the instrument  100 , and the process  1800  continues to  1816  where the instrument  100  is placed in low power mode and the BLUE and GREEN LEDs  118   a, b  are flashed intermittently ON (0.1 s ON and 1.9 s OFF). The Production Test Complete flag remains set to TRUE and the Device Used flag remains set to FALSE. The clip  600 ,  650  is fitted back on the instrument  100 , which is turned OFF and placed in the shipping state. The instrument  100  enters low power mode after the instrument  100  has been activated twice by pressing the activation button  114  or following expiration of the 10 minute timeout period. 
     From  1814 , rather than activating the instrument  100 , a 10 minute timeout period may be allowed to lapse or the clip  600 ,  650  may be fitted back on the instrument  100 . If the 10 minute timeout period is allowed to lapse, the process  1800  continues  1816 . If the clip  600 ,  650  is fitted back on the instrument, the process  1800  continues at  1818 . 
     From  1818 , the instrument  100  may be shipped to the user. Before using the instrument  100 , the user has to remove the clip  600 ,  650  from the instrument  100  and then must activate the instrument  100 . After the clip  600 ,  650  is removed from the instrument  100  but before the activation button  114  is pressed, the process continues at  1820  where the instrument is placed in normal mode but is in idle. The Production Test Complete flag remains set to TRUE and the Device Used flag remains set to FALSE. If the clip  600 ,  650  is fitted back on the instrument  100 , the process  1800  continues back to  1818 . If the activation button  114  is activated, however, the process  1800  continues  1822  where the instrument is placed in normal mode and the RF section is turned ON. Now Production Test Complete flag remains set to TRUE and the Device Used flag is set to TRUE. The instrument  100  only gets marked for disposal (Device Used Flag is TRUE) if the instrument  100  has been activated and the limit switch is pressed during normal mode. If the instrument  100  is now de-activated, the process  1800  continues to  1824  where the instrument is placed in normal mode idle. From  1824 , if the instrument is activated by pressing the activation button  114 , the process  1800  continues at  1822 . From either  1822  or  1824 , if the clip  600 ,  650  is fitted back on the instrument  100 , the process continues to  1826  where the instrument  100  is turned OFF and enters an end of use state. Both the Production Test Complete flag and the Device Used flag remain set to TRUE. The clip  600 ,  650  should be removed at the end of test as a final check to ensure the GREEN LED  118   a, b  comes on. If the RED LED  118   a, b  comes on instead, the instrument  100  has entered self destruct mode. 
     From  1826 , if the clip  600 ,  650  is removed, the instrument  100  initiates discharging the battery  300  and the process  1800  continues to  1828  where the battery  300  continues discharging until the battery  300  is fully discharged at  1830 . From  1828 , the clip  600 ,  650  may be fitted back on the instrument  100 , in which case, the process  1800  continues to  1826 . If any fatal hardware errors occur from any instrument state such as, five short circuits, battery end of life, 8/10 hour timeout, disposal switch  120  is pressed for more than 4 seconds, or the battery  300  initiates discharge, the process  1800  continues to  1828 . 
       FIG. 49-57  illustrates the ornamental design for a surgical instrument handle assembly as shown and described, according to one embodiment. 
       FIG. 49  is a left perspective view of a handle assembly for a surgical instrument. 
       FIG. 50  is a right perspective view thereof. 
       FIG. 51  is a left perspective view thereof. 
       FIG. 52  is a left view thereof. 
       FIG. 53  is a front view thereof. 
       FIG. 54  is a right view thereof. 
       FIG. 55  is a rear view thereof. 
       FIG. 56  is a top view thereof. 
       FIG. 57  is a bottom view thereof. 
     It is worthy to note that any reference to “one aspect” or “an aspect” means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, appearances of the phrases “in one aspect” or “in an aspect” in various places throughout the specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more aspects. 
     Some aspects may be described using the expression “coupled” and “connected” along with their derivatives. It should be understood that these terms are not intended as synonyms for each other. For example, some aspects may be described using the term “connected” to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some aspects may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, also may mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. 
     While certain features of the aspects have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true scope of the disclosed embodiments. 
     Various aspects of the subject matter described herein are set out in the following numbered clauses: 
     1. A medical instrument comprising: a handle for gripping by a user, an end effector coupled to the handle and having at least one electrical contact; a radio frequency (RF) generation circuit coupled to the handle and operable to generate an RF drive signal and to provide the RF drive signal to the at least one electrical contact; wherein the RF generation circuit comprises a parallel resonant circuit. 
     2. The medical instrument according to clause 1, wherein the RF generation circuit comprises switching circuitry that generates a cyclically varying signal, such as a square wave signal, from a direct current (DC) supply and wherein the resonant circuit is configured to receive the cyclically varying signal and wherein the cyclically varying signal is duty cycle modulated. 
     3. The medical instrument according to clause 1, comprising a battery compartment for holding one or more batteries for providing power to the RF generation circuit for generating said RF drive signal. 
     4. The medical instrument according to clause 3, wherein the battery compartment is configured to hold a module comprising the one or more batteries and the RF generation circuit. 
     5. A device according to clause 1, further comprising: battery terminals for connecting to one or more batteries; wherein the RF generation circuit is coupled to the battery terminals; wherein the frequency generation circuit comprises: switching circuitry for generating a cyclically varying signal from a potential difference across the battery terminals; and the resonant circuit, being a resonant drive circuit coupled to the switching circuitry and operable to filter the cyclically varying signal generated by the switching circuitry; and wherein the RF drive signal is controlled by an output from said resonant drive circuit. 
     6. The medical instrument according to clause 1, comprising a control circuit configured to vary the frequency of the RF drive signal. 
     7. The medical instrument according to clause 1, comprising a control circuit configured to vary the amplitude of the RF drive signal. 
     8. The medical instrument according to clause 1, comprising a control circuit configured to vary the duty cycle of the RF drive signal. 
     9. The medical instrument according to clause 8, wherein the control circuit is operable to receive a measurement of the RF drive signal and is operable to vary the frequency of the of the RF drive signal to control the power, voltage and/or current delivered to the at least one electrical contact of the end effector. 
     10. The medical instrument according to clause 9, wherein the measurement is obtained from a sampling circuit that samples a sensed voltage or current signal at a sampling frequency that varies in synchronism with the frequency and phase of the RF drive signal. 
     11. The medical instrument according to clause 10, wherein the frequency at which the sampling circuit is operable to sample the sensed signal is an integer fraction of the frequency of the RF drive signal. 
     12. The medical instrument according to clause 8, wherein the control circuit is configured to vary the frequency of the RF drive signal around the resonant frequency of the resonant circuit. 
     13. The medical instrument according to clause 12, wherein the resonant characteristic of the resonant circuit varies with a load connected to the at least one electrical contact and wherein the control circuit is configured to vary the RF drive frequency to track changes in the resonant characteristic of the resonant circuit. 
     14. The medical instrument according to clause 1, wherein the handle comprises: a control lever to operate the end effector; and an activation button to operate the RF generation circuit and deliver RF energy to the end effector. 
     15. The medical instrument according to clause 14, comprising a rotation knob coupled to end effector to rotate the end effector about an angle greater than 360°. 
     16. The medical instrument according to clause 14, comprising at least one visual feedback element to indicate a state of the medical instrument. 
     17. The medical instrument according to clause 14, comprising an audio feedback element to indicate a state of the medical instrument. 
     18. The medical instrument according to clause 17, comprising an aperture formed in the handle to provide a path for audio waves to escape an interior portion of the handle. 
     19. The medical device according to clause 14, comprising a knife lockout mechanism. 
     20. The medical device according to clause 14, comprising a clip coupled to the control lever. 
     21. The medical instrument according to clause 20, comprising a magnet located within the clip. 
     22. The medical instrument according to clause 21, comprising a magnetically operated element coupled to an electronics system of the medical instrument and a battery of the medical instrument, wherein when the magnet is located within the clip and the clip is coupled to the control lever, the magnetically operated element disconnects the battery from the system electronics.