The HS-27 is a preamplifier headstage which provides 27 channels of unity gain amplification including 24 electrode channels, three reference, and two differential stimulus channels. It is designed to connect to the EIB-27 family of electrode interface boards.
The HS-27-LED is a modified version of the HS-27 includes mounts for colored LED's used with the Cheetah Video Tracker.
Tethers for these headstages are sold separately.