routine  maintenance  of  the  audiovisual ment most frequently used by the Navy. PROJECTION  EQUIPMENT equip- Audiovisual equipment plays a major role in the   Command   Religious   Program.   Religious Program  Specialists  are  required  to  have  the knowledge  and  expertise  to  operate  this  equip- ment   in   support   of   previews   of   audiovisual material;   projectionist   training,   and   volunteer teacher  training;  and  assisting  with  presenta- tions.   This   section   introduces   the   RP   to representative   types   of   still   projection   equip- ment  and  motion  picture  projection  equipment. Although   the   specific   models   of   equipment discussed in this chapter may not necessarily be available,   the   principles   of   operation   are   the same  for  all  models. STILL PICTURE PROJECTORS Many   types   of   still   picture   projectors   are available  for  use  with  presentations.  The  more common   of   these   types   include   overhead, opaque,    lantern-slide,  filmstrip,  and  35-mm projectors.  In  many  instances,  the  RP  will  be required to set up and operate these projectors, as  well  as  prepare  materials  for  use  in  them. Therefore,   it   is   necessary   to   have   a   working knowledge of the operation of the various types of  still  picture  projectors. Overhead Projector The  overhead  projector  shown  in  figure  7-5 is used to project images from projectuals which are  transparent  and  have  a  colored  or  opaque image.  A  desirable  feature  of  the  overhead  pro- jector  is  that  it  may  be  used  in  a  room  without turning  off  the  lights.  Additionally,  the  size  of the  projectual  is  large  enough  to  allow  the instructor  to  work  directly  on  it  while  talking. By writing on clear acetate with a grease pencil, the  instructor  can  create  a  projectual  while teaching a class. The projector can be set up on either side of the  screen.  For  classroom  use,  it  is  normally located  in  front  of  the  screen,  allowing  the instructor   to   operate   it   while   instructing   the class.  For  command  briefings,  the  projector  is usually placed behind the screen so that it offers no  distraction  to  the  audience. Proper  placement  of  the  projector  requires the  operator  to  consider  the  best  possible arrangement  for  each  situation.  Several  points to keep in mind are: 1. The projector should be placed on a table or  stand  at  such  an  angle  that  the  projected image will be nearly a perfect rectangle. Projec- tors  not  properly  placed  will  result  in  an  image that is keystoned (wedge-shaped). In some cases it  may  be  possible  to  adjust  the  angle  of  the screen. 2. Effort should be taken to ensure that each member  of  the  audience  will  be  able  to  see.  It should be kept in mind that the farther the pro- jector is moved from the screen, the less intense the  projected  image  will  be. 3.  Projected  images  should  be  viewed  with- out  having  to  shift  the  eyes  over  too  wide  a range.  Seating  the  audience  at  a  distance  no closer than twice the width of the image will take care of this requirement. The  location  of  the  projector  in  relation  to the  screen  will  also  affect  the  manner  in  which the  projectuals  are  placed  on  the  device.  The bottoms  of  the  projectuals  are  always  placed  so that they are facing the screen. Front projection, where  the  projector  is  located  on  the  audience side of the screen, requires the projectuals to be placed so that they are readable to the operator. Rear  projection,  where  the  projector  is  located behind the screen, requires the projectuals to be placed face down, so that they are unreadable to the  operator. Operation   of   this   projector   is   relatively simple. It involves nothing more than turning on the  projection  lamp,  focusing  the  image,  and positioning the image on the screen. The  projection  lamp  and  blower  motor  may be  controlled  by  a  three-position  switch.  The first  ON  position  provides  power  to  the  blower motor   only;   the   second   ON   position   provides power  to  both  the  projection  lamp  and  the 7-16