as controlled by hand piece 80 buttons 84 86 or a foot switch not shown typically coagulation uses a lower frequency rf signal than does cutting in this case as illustrated the coagulation rf signal applied to lead 158 is at a frequency of 0 46 mhz the other characteristics of this signal are not indicated here since this is merely an indication of the nature of this signal as indicated by the arrow this signal is intended propagate to the coagulation electrodes 104 106 an rf signal of different 4 mhz frequency is applied to lead 160 which is not necessarily connected to lead 158 and this 4 mhz signal is intended to connect to the cutting blade electrode 102 the source of both these rf signals is the rf generator unit 24 shown in fig1 the present inventors have recognized the technical problem that the cutting electrode 102 here lies in close proximity to an arc source electrodes 104 106 useful for large scale coagulation which may lead to breakdown of the gap between the electrodes 102 and 104 or 106 especially when a wet cutting head is partially exposed to air breakdown of this gap e g shorting may cause damage to the delicate cutting electrode and may also result in damage to the power supply unit 24 even if the cutting electrode 102 is connected to ground to protect the rf generator 24.