For all light-signalling devices, the reference axis of the lamp when fitted to the tractor must be parallel with the bearing plane of the tractor on the road and with the longitudinal plane of the tractor.
Kõigi valgussignaalseadmete puhul peab laterna nulltelg pärast laterna traktorile paigaldamist olema paralleelne teel liikuva traktori kandetasapinnaga ja traktori pikitasapinnaga.