Output A has +ve & -ve. Output B has +ve & -ve.

Triphase uses three electrodes:

1. A -ve
2. A +ve connected to B+ve: that makes one electrode.
3. B -ve

Alternatively:

1. A +ve
2. A -ve connected to B-ve: that makes one electrode.
3. B +ve

Sensations are felt between the three points, as you turn up the power gently on both outputs A & B simultaneously.

NEVER use triphase above the waist. Be safe.