In order to purchase an ODFS Pace or O2CHS (two channel) stimulator you have to attend the relevant course i.e. Single channel course for the ODFS Pace and two channel course for the two channel.  Please note that in order to attend the two channel course you have to have completed the Single channel course beforehand.

You can buy the microstim or O4 CHS (4-channel stimulator) or the C-MIT without attending any courses.