by subject to aid in identifying active naval instructions. The index is divided into four sections: 1. 2. 3. 4. Alphabetical  listing–lists  instructions  by  subject content Numerical  listing–lists  instructions  first  by sponsor, then in numerical sequence Recently canceled and/or superseded instruc- tions–lists  all  instructions  recently  canceled  by the  sponsor Navy implementation of Department of Defense (DOD)  issuances–provides  a  cross-reference listing  to  assist  activities  requesting  DOD issuances MAINTAINING TECHNICAL MANUALS Maintaining your technical manuals so they are up-to-date is as important as maintaining any other valuable tool. Your technical manuals must reflect the actual equipment configurations that you have at your command.  An  out-of-date  manual  or  a  manual  that  does not reflect any changes that may have been made to your equipment may prove to be useless when you try to isolate  problems. Changes  or  update  information  you  receive  to NAVSEA  technical  manuals  will  be  in  one  of  three forms: 1) Advance Change Notice (ACN), 2) Permanent Change, or 3) Revision. After receiving any change or update to a tech manual, you should first ensure that the Field  Change,  ORDALT,  SHIPALT  and  so  forth,  is installed in your equipment. If you indicate a change in a manual that is not made in the equipment, the manual will  be  incorrect.  Making  an  incorrect  change  to  a technical manual is as bad as not making a change when one is required. Advance Change Notice (ACN) An ACN is issued when there is an urgent need to add,  correct,  or  expand  information  in  a  technical manual  to  prevent  injury  or  death  to  personnel  or damage  to  equipment.  The  ACN  is  issued  by  the responsible NAVSEA technical activity in response to a known  need  for  immediate  corrective  action. An ACN may be issued as a naval message, a letter, a  NAVGRAM,  or  in  an  Engineering  Information Bulletin  (EIB). When  you  receive  an  ACN,  you  should  do  the following: 1. Determine whether or not the ACN applies to your  technical  manual. 2.  If  it  does  apply,  enter  the  changes  into  your technical manual. 3. Record the entry on the Record of Changes page. Permanent  Change Permanent changes are issued to add system or equipment  configuration  variations  and  new  procedures and  to  change  existing  procedures.  They  are  also  used to highlight outstanding ACNs and to correct other reported   deficiencies. Most permanent changes to technical manuals are identified by a vertical line, known as a change bar, extending along the margin of the changed material. When changes to an entire part, chapter, or section are made, a change bar will not be present. When you receive a Permanent Change, you should take the following steps: 1. 2. 3. 4. 5. 6. Determine whether or not the change applies to the  technical  manual  for  your  system/equipment configuration. Check the Permanent Change Package against the Change Instruction Sheet and the List of Effective Pages to be sure you have a complete set of change pages. Add  replacement  pages  and  new  pages,  and remove   replaced   pages   according   to   the instructions  that  come  with  the  change  package. Record the entry on the Record of Changes page. Destroy the removed pages according to your local  disposal  instructions. Insert  the  Change  Instruction  Sheet  immediately following the title page. Revision A revision is a second or later edition of a technical manual. A revision is issued whenever it is necessary to change the majority of pages in an existing manual. A revision  may  be  required  because  of  hardware modification,  because  of  a  deficiency  that  affects  a  large part  of  the  manual,  or  because  a  change  of  system configuration  results  in  one  volume  or  part  of  a multivolume  or  multipart  set  being  revised. When you receive a technical manual revision, you should: 1.  Verify  that  the  revised  manual  applies  to  your ship, system, or equipment configuration. 2-10