ActiveTwo Auditory Brainstem Response (ABR) Option. Includes: 3 special flat-type active electrodes (Left, Right and Ref) on DIN 8-pole connector and special AUX input on A/D box front panel. These special flat electrodes use the same housing as standard flat-type electrodes, but use a different amplifier optimized for high frequencies. In addition, there is a factor of 1600 gain on the electrode (compared to unity gain on the standard ones). ABR module generates two differential signals (Left versus Ref, and Right versus Ref) — no software re-referencing required. Specifications: noise is 2 uVpp in a bandwidth 100 Hz to 3.3 kHz, AC input range 5 mVpp (AC amplification), DC input range 500 mVpp, CMRR is 160 dB @ 50 Hz.