Source google image: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Va_et_vient4.png/400px-Va_et_vient4.png
Schema 6 electrique
Source google image: https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Va_et_vient4.png/400px-Va_et_vient4.png