An assembly of devices used to apply precisely timed and repeatable electrical stimuli to the peripheral nerves, typically for evoked potential and other research procedures (e.g., functional mapping in epilepsy). It is usually a multichannel external stimulation system, consisting of external surface electrodes or invasive (i.e., needle) electrodes, and a pulse generator. It may be used as a component of more complex devices such as somatosensory evoked-potential recording systems.