MICROFILM/APERTURE CARDS Many prints and drawings are procured in the form of  16-  and  35-mm  microfilm.  Microfilm  prints  and drawings are available mounted on aperture (viewer) cards, as well as in roll form. A reader or some type of projector   is   required   to   enlarge   the   microfilm   for reading.   Activities   are   provided   with   a   microfilm reader-printer, which as its name implies, enlarges the microfilm  for  reading  and  also  has  the  capability  of printing a working copy in a matter of a few seconds. Microfilm  greatly  reduces  the  size  of  otherwise bulky files, which is very important aboard ship. SCHEMATIC DIAGRAMS Schematic diagrams show by means of single lines and symbols how the parts of a system are connected for the operation of the system. Piping Piping diagrams are normally used to trace piping systems and their functions without actually describing the shape, size, or location of the components or parts. Each component is represented by a symbol; and once these   symbols   are   learned,   the   piping   schematic diagram is easy to read. Figure 1-7 is a good example of a piping diagram. As  may  be  seen  from  this  example,  diagrams  do  not indicate the location of individual components within the station, but do locate the components with respect to each other within the system. Electrical Schematic    diagrams    are    also    used    to    depict electrical  systems.  They  are  basically  the  same  as  the 1-8 PHANTOM  LINE CENTER   LINE DIMENSION   LINE OUTLINE HIDDEN   LINE CUTTING  PLANE  LINE BREAK   LINE EXTENSION   LINE LEADER   LINE SECTIONING   LINE SECTION  - AA ABEf0175 A A Figure 1-6.—Use of standard lines. COOLING  PANEL ABEf0176 8 9 7 10 P M.C. CATAPULT CONSOLE 11 12 6 5 P 3 4 2 13 1 FIREMAIN OVERBOARD Cutout  valve. Reducing  valve Throttling  valve. Relief  valve. Test  gauge. 1. 2. 3. 4. 5. Hytrol  valve. Pilot  valve. Inlet  lines. Discharge  lines. Pressure  gage. 6. 7. 8. 9. 10. Orifice. Scupper valve. Hose valves. 11. 12. 13. Figure 1-7.—Typical piping schematic for saltwater cooling.