TRANSDUCER SPECIAL INFORMATION The    550-and    530    are    supplied    with    a    high    speed transducer    with    20-toot    cable,    and    transom    mount brackets.   (Optional  12-ft.   cable  extension  is  available.) The  High  Speed  Transducer  can  also  be  used  inside  a solid fiberglass or aluminum hull, by placing it in a water well   or   cementing   it   to   the   inside   of   the   hull.      (See separate   instructions   provided   with   the   transducer.)   If another   type   of   200   KHz   Aqua   Probe   transducer   is preferred, it can be substituted with no retuning. OPERATION Your    Aqua    Probe    digital    depth    instrument    has    an advanced    version    of    Aqua    Meter's    exclusive    DRR (Delayed Receiver Recovery) circuit which was pioneered  in  the  Aqua  Meter  "Cheater"  line  of  shallow water   depth   fishfinders.      This   unique   circuit   virtually eliminates   erroneous   false   echoes   due   to   all   but   the most  severe  subsurface  interference  and  thus,  the  false readings that they cause. Proper     adjustment     of     the     sensitivity     control     (and mounting of the transducer, which is-detailed later in this manual)  unquestionably  is  the  most  important  factor  in obtaining  optimum  performance  from  any  depth  finder. Unlike  some  competitive  units  that  do  not  provide  any way  for  the  operator  to  adjust  the  sensitivity,  your  Aqua Probe   digital   unit   combines   overall   gain   adjustment, subsurface interference rejection adjustment, and vernier automatic gain limiting in one master SENSITIVITY knob. The following procedure should be completely understood  through  actual  operating  experience.    Once that experience has been achieved it will be obvious how logically    the    Aqua    Probe    digital    depth    instrument controls, switches, and operating functions are arranged. 1.  PRE-SET THE CONTROLS: It  is  best  to  preset  all  controls  before  you  attempt  to operate the unit. Turn the:   POWER SWITCH (Light-Oft-On) to center, off position;   All other switches should be in the down position;   SENSITIVITY and SHALLOW alarm knobs to minimum settings;   DEEP alarm knob (on model No. 550 only) to its maximum setting. 2.  TURN ON Switch the POWER toggle (LIGHT-OFF-ON) down to the ON position.  At this point, on all models, an Aqua Meter logo should  appear  on  the  left  side  of  the  Liquid Crystal  Display  (LCD).    It  serves  as  an  "on"  indicator  in much the same way that a pilot light does on older types of   electronic   equipment.      If   it   is   dusk   or   night   time, instead of moving the power switch down to "ON", move it  up  to  LIGHT.    In  this  case,  the  unit  will  come  on,  the logo will appear and the night light will illuminate the LCD  with  a  soft  red  glow.    The  Aqua  Meter  exclusive LCD   has   a   special   reflective   polarizer   which   not   only improves   contrast   during   daytime   operation,   but   also serves to distribute the night-light more uniformly across the display under low-light conditions. The   electrical   current   drain   with   the   power   switch   to "ON"  is  less  than  0.2  amp,  and  this  position  should  be used   whenever   battery   reserve   must   be   conserved. With    the    night-light    activated,    the    current    increases slightly, but is still less than 0.3 amp. If   your   unit   is   a   model   No.   540   digital   remote   it   is necessary to turn on the "main" depthfinder, to which the No. 540 is connected before the No. 540 will function. The  models  No.  530  and  540  will  display  only  the logo. The  model  No.    550  will  display  the logo  and  the words  "No  Echo"  in  the  lower  left  corner  of  the  LCD  at "zero" sensitivity.  (See "Quick 9