A training adapter (28) for an automated external defibrillator (AED) (10) which provides for safe training use of any AED. The training adapter includes a circuit which ensures that any defibrillation voltage/current is shunted away from the trainee, training electrodes (26), and patient simulation equipment. The training adapter simultaneously provides to the AED a simulated patient ECG signal which causes the AED to operate as if an actual cardiac rescue were occurring, thus heightening the realism of the training experience.