An external pacemaker with at least one electrode temporarily connectable to the heart, and at the distal end of which is an active region, which makes contact with heart tissue, and at the proximal end is a contact plug. The electrode is for transmission of stimulation, defibrillation, and/or cardioversion pulses and is plugged into a pacemaker plug socket. The contact plug has first and second contact regions at its plug part. The plug socket matches the contact plug with two mating contacts, the first for transmitting stimulation pulses and the second for transmitting defibrillation and/or cardioversion pulses. In the plugged-in position, only the contact region on the plug part makes contact with the mating contact provided for transmitting the defibrillation and/or cardioversion pulses, such that no defibrillation and/or cardioversion pulse can be transmitted to electrodes which are unsuitable for defibrillation and/or cardioversion and have only a single-stage contact plug.
