TM 1-1510-225-10 1-2 c.   Illustration  Changes.    A  miniature  pointing hand   symbol   is   used   to   denote   a   change   to    an illustration.      However,   a   vertical   line   in   the   outer margin,  rather  than  miniature-pointing  hands,  is  used when there have been extensive changes made to an illustration. 1-11.  AIRCRAFT DESIGNATION SYSTEM. a.   The designation system prescribed by AR 70-50 is used in aircraft designations as follows: b.  Example C-12R: C –  Basic mission and type symbol (Cargo) 12   –  Design number R –  Series symbol 1-12.  AIRCRAFT EFFECTIVITY DESIGNATORS AND SERIALIZATION. The   aircraft   effectivity   for   content   within   this manual  will  be  designated  by  the  following  symbols.   These symbols may be used individually or in groups. R All C-12R aircraft. T3 Aircraft     with     serial     numbers     84-0143 through 84-0182 or serial numbers 84-0484   through   84-0489  modified  with the  cockpit  and  digital  engine   instrument upgrade. F3 Aircraft     with     serial     numbers     84-0143 through 84-0182 or serial numbers 84-0484   through   84-0489   not   modified with the cockpit and digital engine instrument upgrade. OSA Operation Support Airlift aircraft with serial numbers 84-0143 through 84-0182 issued from the U.S. Air Force. ANG Aircraft     with     serial     numbers     84-0484 through    84-0489    issued    from    the    Air National Guard. The     effectivity     symbols     listed     are     used     in conjunction with paragraph titles, text content, performance  charts  and  graphs,  tables,  figure  titles, and   specific   items   on   illustrations   to   show   proper effectivity of the material as applicable.  If the material applies  to  all  models  within  the  manual,  no  effectivity designators    are    used.        Where    practical,    to    avoid duplication,  descriptive  information  is  written  to  apply to all models and split series effectivities. 1-13.  USE   OF   WORDS   SHALL,   SHOULD,    AND MAY. Within  this  technical  manual,  the  word  "shall"  is used  to  indicate  a  mandatory  requirement.    The  word "should"    is    used   to    indicate    a    nonmandatory    but preferred method of accomplishment.  The word "may" is     used     to     indicate     an     acceptable     method     of accomplishment. 1-14.  PLACARD ITEMS. Where   applicable,   placarded   items   (switches, controls,  etc.)  are  shown,  throughout  this  manual,  in boldface capital letters. 1-15.  AVIONICS CHAPTERS. This    manual    contains    five    Avionics    chapters entitled as follows: Chapter 3 Avionics   —   Avionics   common   to all     C-12R,     C-12T3, and C-12F3 Aircraft Chapter 3A Avionics —  C-12R Aircraft Chapter 3B Avionics   —  C-12T3 Aircraft Chapter 3C Avionics   —  C-12F3 Aircraft Chapter 3D Global Positioning System —  C-12R     and     C-12F3 Aircraft 1-16.  NORMAL PROCEDURES. This   manual   contains   two   Normal   Procedures chapters entitled as follows. Chapter 8 Normal Procedures –  C-12R Aircraft Chapter 8A Normal Procedures    –  C-12T3 and C-12F3 Aircraft