H21B4 (Fairchild Semiconductor) PHOTODARLINGTON OPTICAL INTERRUPTER SWITCH PHOTODARLINGTON OPTICAL INTERRUPTER SWITCH H21B4 PACKAGE DIMENSIONS 0.972 (24.7) 0.957 (24.3) H21B5 H21B6 0.472 (12.0) 0.457 (11.6) C L Ø 0.133 (3 (31 views)