Brain-Trainer sells both 4 and 2 channel hardware. Channels can be assigned to any 10-20 site on the scalp. NeuroOptimal is a 2 channel system at C3, C4 locations.
However also note that the Q-Wiz 4 channel amp sold by Brain-Trainer, has a 25 pin connector (DB-25), that allows full cap assessments to be easily done. Four channels at a time, but switched electrically. Full cap QEEG is typically 19+ channels / sites. Pete uses a couple additional sites (Fz Oz ?) Doing a QEEG like this gives basic amplitudes, but not coherence beyond the 4 channels being recorded. Normal 19+ channel QEEG amps (such as Brainmaster, etc.) sample all 19 channels at once. Thus give whole head coherence. And can also compute 3D voxels with appropriate sLoreta software.
