TM 55-1510-222-10 ECCM operational mode.  Available also are a number of  built-in  test  and  status  words  indicative  of  internal conditions within the RT. (6) Keyboard.  The 15-button keyboard is used  to  insert  or  display  data,  depending  on  the  key switch  actuated,  and  the  positions  of  the  MODE  and function  switches.    The  keyboard  is  comprised  of  10 numerical  buttons,  three  special  function  buttons,  and two   command   buttons.      The   three   special   function buttons  are  located  on  the  right  side  of  the  keyboard. The  two  command  buttons  (CLR  and  ENT)  are  located on either side of the numerical zero button.  The special function  buttons  will  always  initiate  a  display  according to  the  function  of  the  button  pressed.    Pressing  TIME, will display time, pressing FREQ, will display frequency, etc.    Pressing  CLR  will  clear  only  the  displayed  data. Pressing   ENT   will   enter   the   displayed   data   into   the system and is always signaled by a momentary blink of the   display.      When   the   CLR   button   is   pressed,   the displayed  digits  (two,  four  or  five  dependent  upon  the displayed information) will have the number replaced by a   horizontal   line   at   the   bottom   of   each   digit.      This underline  feature  aids  the  operator  in  knowing  where entered data will appear. (a) Switches  1  through  9.    Digital inputs    are    used    to    key    in    frequency,    load    time information, or offsets.  Entry of information is normally digit-by-digit displayed left to right on the readout.  It is to be noted that operation of the RT is not altered until complete,  valid  data  is  registered  on  the  readout,  and the  keyboard  ENT  button  depressed  within  the  seven second  time-out  period.    Incomplete  entries  will  not  be accepted  when  ENT  is  pressed.    Acceptance  of  valid data  is  signaled  by  a  momentary  blink  of  the  display when ENT is pressed.  Partial or mistaken data may be erased at any time by pressing CLR, at which time the last  readout  will  be  cleared.    Manual  frequencies  can only    be    selected    with    the    function    switch    in    an operational position and the MODE switch in SC.  With the  function  switch  in  LD  and  the  MODE  switch  in  SC, new  preset  frequencies  may  be  entered  in  conjunction with   the   numbered   positions   of   the   PRESET   switch. With the function switch in LD; TIME may be entered or altered by pressing TIME, then CLR. (b) 0 (H LD).  The 0 (zero) switch is used  to  enter  zeros  in  the  same  manner  as  defined  in switches I through 9.  However, it has a second function; (H LD) which initiates transfer of ECCM parameters. (c) CLR.    The  CLR  button  is  used to zeroize the display.  CLR must be pressed to remove the old data from the display prior to entering new data during   LD,   or   changing   frequencies   during   a   manual operation. (d) STO/ENT. The STO/ENT button  is  used  to  initiate  entry  of  all  data  by  keyboard entry.      In   all   cases,   only   valid,   complete   entries   will enable the STO/ENT button.  Successful initiation of the entry  action  will  always  be  signaled  by  a  blink  of  the display. STO/ENT   has   a   second   function   of   storing   a received hopset or lockout set held in holding memory. Selection of the preset (I through 6) is necessary. (e) FREQ.      The   FREQ   button   is used  to  display  the  current  operating  frequency  during single  channel  (manual  or  preset)  operation.    It  is  also used    in    loading    preset    frequencies,    however,    the function   switch   must   be   in   the   LD   (load)   position. Whenever the button is pressed, frequency is displayed, and  an  entry  sequence  is  initiated  involving  frequency. If   the   frequencies   stored   within   the   radio   had   been zeroized   (ZA   on   the   function   switch),   FILL   and   the preset number will be displayed when FREQ is pressed, until new valid frequencies are entered.  If the operating frequency   currently   in   use   has   been   offset,   the   true operating    frequency    (plus    or    minus    offset)    will    be displayed. (f) SEnd/OFST.    The  SEnd/OFST (offset)   button   is   used   to   modify   a   single   channel operating   frequency,   manually   selected   or   preset,   to include  offsets  of    5  or    10  kHz.    The  offset  to  be applied  to  the  basic  frequency  is  displayed  by  itself  in the  two  right  digits  of  the  display.    The  function  switch can be in any operational position, however, the MODE switch must be in SC to apply offsets.  Pressing OFST will immediately display any current valid offset applied to   the   selected   single   channel   frequency.      Negative offsets are indicated by a negative sign (-) appearing in the  center  digit  position.    Positive  offsets  are  indicated by no prefix.  No offset is indicated by 00 in the two right digits.      To   apply   an   offset,   the   OFST   button   is   first pressed.    The  CLR  button  must  then  be  pressed.    If  a negative offset is desired, OFST button is first pressed. A  negative  sign  will  appear  in  the  center  digit  position. Repeated pressing of OFST will alternate between plus and minus offsets.  The keyboard must now be used to insert   either   five   or   ten.      If   five   is   pressed,   05   will automatically appear.  If 10 is required, 1 then 0 must be pressed.  All other 3-15