signal is not hoisted to the dip; instead it is hoisted closed  up  after  the  signal  is  understood  by  the appropriate  personnel. Question To question signals from the INCSEA agreement, the signal YVpl TACK ZLp3 will be used. Cancel To cancel signals from the INCSEA agreement, the code pennant followed by either  YN  or ZP  must precede the group that cancels. SPECIAL WARNING SIGNALS To inform foreign naval vessels that they have violated  Soviet  spaces,  will  use  the  warning  signals listed below: SNG SNO SNP SNR You have violated the state border of the Soviet Union. I demand that you leave Soviet Union waters immediately. I demand that you leave the waters of the Soviet Union immediately. Unless you do so, a force of arms will be used against you. You are violating the regulations for navigating and  remaining  in  Soviet  Union  waters.  I demand that you cease violations. Despite warnings, you continue to violate the regulations for navigating and remaining in Soviet Union waters. You are to leave them immediately. During the day, these signals will be made by flags. During nighttime, these signals are made by Morse code using a signal lamp. Radiotelephone may also be used to transmit the signal, as well as voice using a megaphone or any other amplifying device. WARNING SIGNALS TO SUBMARINES The signal of two series of explosions with three explosions in each series (where the interval between the explosions in a series is 1 minute and the interval between the series is 3 minutes) means “You are in Soviet  Union  waters.  I  demand  you  surface immediately.  Unless  you  comply  with  this  order within 10 minutes, a force of arms will be used against you.” An  acoustic  signal  by  sonar  may  be  given simultaneously,  with  the  same  meaning  as  stated previously. The signal will consist of five dashes, each dash 3 seconds long, and the interval between dashes, 3 seconds. INDEX LEARNING  OBJECTIVES:  Explain   the procedures for the use of the index. The  index  is  divided  into  two  separate  indexes: Index 1 is the Signaling Instructions and General Signal Code and Index 2 is the Medical Signal Code. USE AND CONSTRUCTION OF GROUPS The types of signals used are the following: Single-letter   signals—Indicate   very   urgent, important, or very common use Two-letter  signals—The  general  code Three-letter signals—Begin with M and indicate the medical code The Code follows the basic principle that each signal should have a complete meaning. This principle is followed throughout the Code. In certain cases, complements are used when necessary to supplement the available group. To  find  a  certain  group  when  encoding,  always turn first to the signal index or medical index, as appropriate, and pick out the key word or phase. Examples: Do you require a boat? KEY WORD: Boat Explosion has occurred in tank. KEY WORD: Explosion COMPLEMENTS  EXPRESS The  use  of  complements  is  explained  in  the following paragraphs. You as a Signalman must know how  to  use  complements  to  effectively  communicate with  merchantmen. Variations  in  the  meaning  of  the  basic  signal: CP—I am (or vessel indicated is) proceeding to your  assistance. 6-19