Reference is placed on Cz on the demo montage and this is a common reference for all EEG channels. As the reference electrode design is similar to the others medelopt EEG electrodes, the reference electrode position on the scalp can be changed. Note that the reference can be changed online in ElOpt, in the “EEG check” tab. However, it will lead to 1 EEG channel loss as the electrode will be used as the reference. We advise to change the reference offline, during the post-processing of the EEG data.