TM 55-1510-222-10 buttons will be inactive and nothing will be registered if accidentally pressed.  Once the valid offset is registered on   the   display,   along   with   a   plus,   (no   indication)   or minus sign, the ENT button is pressed.  The display will momentarily  blink,  signaling  acceptance  and  initiating frequency  offset  immediately.    If  the  FREQ  button  is pressed at this point, it will display the original operating frequency with the offset subtracted or added to it.  To cancel  an  offset,  press  OFST  first  to  display  existing offsets.  Then press CLR followed by 0, which will cause 00 to be displayed.  When ENT is pressed, an offset of 00  is  entered  returning  the  operating  frequency  to  its nonoffset condition. SEnd/OFST has a second function of initiating an ERF  transmission  if  a  hopset  or  lockout  set  is  in  the holding  memory  and  the  mode  switch  is  in  the  FH-M position. (g) TIME.  The TIME button on the keyboard  is  used  to  display  or  change  the  time  setting maintained  within  each  RT.    Time  is  displayed  in  three separate  individual  fields  in  days  (O  through  99)  hours and  minutes  hours  (O  through  23),  minutes  (O  through 59) and seconds (O through 59).  Days are displayed in the  two  left  digits  immediately  when  TIME  is  pressed. Pressing  TIME  again  will  cause  the  field  to  change  to the hours/minutes field.  Hours are displayed in the two left  digits  of  the  second  field,  minutes  in  the  two  right digits.  Pressing TIME the third time results in the third (minutes/seconds)  field  being  displayed.    Minutes  are displayed    in    the    two    left    digits    and    seconds    are displayed  on  the  two  right  digits  of  the  display.    When TIME  is  displayed  and  CLR  has  not  been  pressed,  the seconds  will  be  running.    When  CLR  is  pressed,  the internal  clock  continues  to  run,  but  the  display  will  be static, displaying entry information only.  To set or reset time,   requires   that   the   function   switch   be   in   the   LD (load)    position.        The    positions    of    the    MODE    and PRESET  switches  are  of  no  consequence.    With  the function switch in LD, the TIME button is pressed once, displaying days in the two left digits.  Press CLR (clear) and   the   two   digits   will   be   removed.      The   new   days numbers may then be inserted by keyboard entry.  Once the  new  days  numbers  have  been  registered,  the  ENT button   is   pressed   and   the   display   caused   to   blink momentarily.    The  new  days  numbers  are  now  entered and stored.  Once the new days have been entered, the TIME  button  must  again  be  pressed  to  change  to  the second  field  (hours  and  minutes).    The  previous  hours and  minutes  are  displayed  in  the  two  extreme  left  and right   digits,   respectively.      CLR   is   then   pressed   to remove the old hours/minutes display and is replaced by underlines    at    the    bottom    of    each    digit    previously displaying   a   number.      The   new   hour   and   minute numbers   (four   digits)   are   then   entered   by   keyboard entry.  Once ENT is pressed, the display blinks and the new  data  is  registered.    When  the  new  hours/minutes numbers   are   registered,   the   registered   numbers   are static and displayed time is not changing.  When ENT is pressed,  time  keeping  is  started,  and  the  seconds  are zeroed  prior  to  the  new  time  keeping  procedure.    The third   display   field   (minutes/seconds)   is   available   for display,  but  cannot  be  set  by  keyboard  entry.    Only when  a  valid  four  digit  hours/minutes  entry  has  been completed by pressing ENT is the old seconds erased to zero  and  new  time  started.    This  is  to  accommodate presetting and display of time prior to a time mark.  If an error  occurs  during  any  entry  sequence,  pressing  CLR erases the display and starts the sequence over. (7) FILL.    This  connector  is  used  to  fill ECCM parameters from an external fill device.  Entry of ECCM parameters is initiated by the H LD button on the keyboard  with  the  function  switch  in  LD  or  LD-V.    The RT  will  recognize  the  attachment  of  a  fill  device  and respond accordingly. 3-13.  EMERGENCY LOCATOR TRANSMITTER (ELT). a. Description. An emergency locator transmitter  is  provided  to  assist  in  locating  an  aircraft and    crew    in    the    event    an    emergency    landing    is necessitated.  The output frequency is 121.  5 and 243 MHz  simultaneously.    Range  is  approximately  line-of- sight.  The transmitter unit has separate function control switches  located  on  one  end  of  the  case.    In  the  event the  impact  switch  has  been  inadvertently  actuated,  the beacon  can  be  reset  by  firmly  pressing  the  pushbutton RESET  switch  on  the  front  of  the  case.    The  RESET switch  and  a  3-position  toggle  switch,  placarded  ARM, OFF  and  ON,  also  on  the  transmitter  case,  may  be actuated by inserting one finger through a small, round, spring-loaded  door  on  the  left  side  of  the  aft  fuselage (fig.  3-6).  The transmitter unit is accessible through a service panel located on the bottom of the aft fuselage. 3-16