Average Reference Amplifier
The amplifier architecture that is used in the majority of TMSi systems is called the Reference Amplifier. When implemented correctly, it offers significant advantages over other amplifier designs.
TMSi uses average referencing as default because this makes it possible to re-reference in software to any montage you want.
In this amplifier design, the mean of all the connected electrodes is used as the reference signal. In most other amplifier systems, the common reference concept is used, which means that 1 specific electrode is used as the reference signal. The downside of this common reference concept is that when the common reference electrode has a bad contact, it influences all the other electrode signals. With the average reference concept you can just choose an electrode afterwards to be the common reference.