An assembly of devices designed to locate a facial nerve by applying an electrical stimulus with a probe and comparing muscle responses as the probe is moved. It typically includes an electrical pulse generator, appropriate electrodes, sensors to detect muscle response (e.g., a strain gauge, electrical sensors), and audible and/or visual indicators. The system generates rectangular- and possibly triangular-waveform currents to stimulate nerve fibres and produce muscular contraction. It is used during diagnosis and assessment of nerve function, to locate nerves during surgery reducing the chance of accidental injury, and to monitor the progress of nerve regeneration after surgery.