Patent ID: 8876816

Claim:
An electrosurgical system comprising: a first unit including a generator for generating radio frequency (RF) power, and a second unit including at least part of an electrosurgical instrument associated with the generator, the second unit being detachably electrically connectible to the first unit such that RF power can be conveyed to the second unit; wherein the second unit includes a passive electrical identification component having a parameter of a finite non-zero value identifying the second unit; and wherein the first unit comprises a sensing circuit including a second passive electrical component, a signal source arranged to provide a voltage step-change, and a signal detector, such that when the second unit is connected to the first unit, the signal source provides a voltage step-change to the passive electrical identification component, the passive electrical identification component and the second passive electrical component forming a resonant circuit such that the voltage step-change causes the resonant circuit to produce a resonant ringing signal at a resonant frequency which is dependent on the parameter value of the passive electrical identification component, the first unit further corn rising third passive electrical component connected to the second passive electrical component so as to cause the resonant ringing signal to decay over time, and a signal detector that detects a characteristic of the ringing signal to generate a detector output signal representative of the parameter value, the first unit further comprising a controller connected to the sensing circuit to receive the detector output signal, the controller being configured to identify the second unit in response to the detector output signal.