In an electrosurgical system having a generator for generating radio frequency(RF) power and an electrosurgical instrument, the instrument includes a passiveelectrical identification component (14) having a parameter of finite non-zerovalue identifying the instrument. The generator has a sensing circuit (24) witha second electrical component (38), a signal source (36) providing a voltagestep-change, and a signal detector (46, 48) for detecting a transient responseof the combination of the identification component and the second electricalcomponent, the detector output signal being representative of the parametervalue thereby allowing automatic identification of the instrument when it isconnected to the generator. Also disclosed is an electrode assembly in whichthe identification component is associated with a digital device includinga memory, the instrument having a pair of contacts interconnected by the identificationcomponent and serving to supply power from the generator to the digital deviceand/or convey data from a data output of the digital device.
