Abstract: A radio-frequency electrosurgical device which includes an active electrode, a passive electrode, and a radio-frequency generator. The radio-frequency generator induces a radio-frequency potential on a primary winding of an isolation transformer. The secondary winding of the isolation transformer powers the active electrode. One end of the second winding of the isolation transformer is coupled to a return lead connected to the passive electrode and also is coupled to ground through a primary winding of a second transformer. If the passive electrode is disconnected from the return line, there can be an alternate radio-frequency current return path to ground, and a potential is developed across the primary winding of the second transformer. This potential is used to energize a relay to actuate an alarm and to disable the radio-frequency generator if the passive electrode becomes disconnected.