TM 55-1510-220-10 2. RMT/LOCAL/SIG CLR switch RMT. 3. PWR/FILL   switch   Set   to   desired   fill register. 4. Microphone switch Press.  Wait for the preamble   to   stop,   then   talk   into   the microphone. 5. Microphone  switch  Release.    Wait  for the postamble to stop. NOTE The    SIG/CIPHER    RCV    indicator light    (fig.        3-8)    will    flash    during receipt of secure voice communications.      After   receiving   a secure communications, wait until the postamble  stops  before  initiating  any transmission. (5) TSEC/KY-75 clear voice operating procedure: 1. PLAIN/CIPHER switch PLAIN. Check that PLAIN indicator light illuminates. 2. RMT/LOCAL/SIG  CLR switch RMT. 3. Microphone     switch     Press     to     talk, release when finished. (6) Zeroizing TSEC/KY-75. 1. PWR/FILL   switch   (fig.      3-8)   OFF/ ZEROIZE. NOTE All three fill registers of the TSEC/KY75 will be zeroized simultaneously. 2. The steady alarm tone should be heard if  the  PWR/FILL  switch  is  set  to  any fill position. NOTE When aircraft power is not applied to the  TSEC/KY-75  and  the  standby  fill batteries  have  been  removed  or  are too   weak   to   maintain   the   memory circuits,   all   storage   registers   of   the TSEC/KY-75  will  be  zeroized  within approximately 45 seconds. 3-16.   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  right  side  of  the  aft  fuselage  (fig. 3-9).    The  transmitter  unit  is  accessible  through  a  service- panel located on the bottom of the aft fuselage. b. Controls and Functions. (1) RESET switch. When pressed, resets transmitter. (2) Function  switch.    Selects  operating  mode  of set. (a) ARM.      Arms   set   to   be   actuated   by impact switch (normal mode). (b) OFF.  Turns set off. (c) ON. Manually activates transmitter for test or emergency purposes. 3-19