An electrosurgical system comprises at least a first unit (1) and a second unit (3), the second unit (3) being detachably connectible to the first unit (1) and including an electrode assembly (15). The first unit comprises a power supply (10), an RF oscillator circuit (11) for generating a radio frequency output, and an output stage (13) adapted to supply an RF output to the electrode assembly (15). The second unit (3) comprises an identification circuit (16) presenting, in an alternating manner, a parameter with a first finite non-zero value for a first time period, and a parameter with a second finite value for a second time period. The first unit (1) includes a sensing circuit (18) and a controller (12) adapted to detect a characteristic of the identification circuit and provide an output signal, the controller (12) connected to the sensing circuit and receiving the output signal, adjusts the RF output so as to suit the particular electrode assembly (15).