cartridge holder and slide the cartridge into posi- tion.  You  can  project  the  filmstrip  without  the cartridge by placing the filmstrip roll in the car- tridge  holder  with  the  leading  edge  of  the  film feeding  from  the  top.  Replace  the  cartridge  lock and  close  the  front  access  door.  You  are  now ready  for  focusing,  framing,  and  advancing  the film. OPERATION.—The   projector   power   switch is on the top of the projector directly behind the carrying   handle. It   is   a   three-way   switch operating   the   fan   in   the   COOL   position   and both  the  fan  and  the  lamp  in  the  LAMP  posi- tion.  Turn  the  film  advance  knob  counter- clockwise until an image appears on the screen. Adjust the focus until the image is sharp. Frame the image by moving the framing level to either side until the full image is on the screen. You  must  center  and  level  the  image.  This projector has a tilt knob which adjusts the eleva- tion  of  the  image.  Raise  or  lower  the  projector by   turning   the   knob   counterclockwise.   This releases  the  spring-tensioned  foot.  Lock  this foot  by  turning  the  knob  clockwise.  Level  the projector  by  applying  downward  pressure  to either  of  its  sides.  The  projector  is  now  set  up. After  completion  of  the  presentation,  rewind the   filmstrip   by   the   rewind   crank.   Open   the rewind  crank  from  the  film  advance  knob. CLEANING    AND    MAINTENANCE.— Preventive maintenance is the best way to keep any piece of AV equipment in top operating con- dition.   To   clean   the   optics   of   the   projectors, open  the  lamp  house  cover,  after  first  discon- necting the power cord. Remove the lamp house by loosening the release screw on the lamp house cover.  The  various  condensers  and  heat  filters are held in place by a spring clip which, in turn, is  held  in  place  by  a  screw.  After  loosening  the screws,  lift  out  the  spring  clip.  Remove  the optics   and   clean   them   with   a   lint-free   cloth, moistened   with   lens   cleaner.   Reverse   the removal process to replace the optics in the pro- jector.  Clean  the  lens  in  the  same  manner  that you  clean  the  other  optics.  The  film  track  and pressure plate should be wiped with a clean, lint- free   cloth   moistened   with   acetone   or   alcohol, These  solvents  are  very  good  for  removing  dirt and  emulsion  from  the  film  path. MOTION PICTURE PROJECTORS As  a  Religious  Program  Specialist,  you  will normally  be  required  to  operate  motion  picture projectors.  A  projectionist  is  a  key  member  of  a presentation team responsible for the operation, cleanliness,  and  routine  maintenance  of  the audiovisual equipment, and the general appear- ance   of   the   presentation   room.   Whether   an audience profits from a presentation depends, to a large extent, on you. In order to assure a pro- fessional  presentation,  you  must  maintain  high standards  at  all  times  because  you  control  the projection   and   sound   reproduction   equipment. You   should   also   refer   to   ART   1410440, MILPERSMAN,  which  states  how  you  may become designated as a motion picture operator. Programmed courses of instruction are available which  can  provide  the  information  necessary  to become   a   qualified   16-mm   projector   operator, which  will  satisfy,  in  part,  the  requirements  of ART   1410440,   MILPERSMAN.   These   courses may   be   obtained   through   your   Educational Services  Office. Principles of the Motion Picture The  motion  picture  is,  in  reality,  a  series  of still  pictures,  projected  successively  at  such  a rate of speed that it gives the illusion of motion. When the, eye is permitted to see an object for an instant  after  which  the  object  is  removed  and obscured,  the  eye  will  continue  to  see  an  image of  the  object  for  approximately  one-fortieth  of  a second  thereafter.  This  is  called  the  persistence of vision. If a series of still pictures is projected, in which the same object is seen in a slightly dif- ferent  position  in  each  picture,  the  eye  will merge the sequence into one continuous motion. The  purpose  of  a  motion  picture  projector  is  to project   a   sequence   of   images   upon   a   screen. However,   the   projector   not   only   projects   the pictures on the screen, but it synchronizes sound with the picture. 16-mm  Motion  Picture  Projector The  most  common  size  of  film  produced  and employed by the Navy for motion pictures is the 7-25