An electrocautery (electrosurgery) in which an electric current is applied through a hand-held active electrode and travels back to the generator through an inactive electrode attached to the patient (the grounding pad), so that the patient is part of the electrical circuit.

1. An electrocardiogram taken with the exploring electrode placed on the chest over the heart or upon a single limb, the indifferent ("zero" potential) electrode being the central terminal.
2. An electrocardiogram that shows the potential detected by a single electrode.

In practice, this is obtained by using an exploring electrode and a second electrode; such as, a central terminal that is assumed to have zero potential.