PSSu A CE “A” yellow (10 pcs.) 312903 PSSu, coding elements for FS I/O and basic module, yellow, coding A, PU 10 pieces, packed in resealable polybag with marking sticker. The automation system PSS 4000-R makes it extremely easy for you to implement safe rail automation! Find out more about the PSS 4000-R from Pilz.