center  or  work  group  supervisory  position.  Your  positive attitude and confidence will be an asset, and in time, you will  become  more  proficient  in  managing  the maintenance  for  the  additional  equipment  and  systems. It  is  almost  impossible  to  become  a  proficient technician in all electronic equipments and systems; however, as a supervisor, you should have adequate knowledge of all the electronic equipments and systems for which you are responsible. Additionally, you should have at least a functional knowledge (as a minimum) of all  peripheral,  ancillary,  and  supporting  equipment  and systems. As   a   supervisor,   you   should   know   where   all equipments are located, their designations, and their position  numbers.  Your  casualty  control  folder  should help you find equipment locations. With time, as you apply  yourself  as  a  conscientious  supervisor,  identifying and  explaining  locations,  functions,  and  system operation  will  become  second  nature  for  you. A good background knowledge of all equipments and   systems   combined   with   your   maintenance experience  and  positive  and  confident  attitude  will  be assets as you work in the following areas: Training  your  technicians  (and  yourself) Minimizing  equipment  and  system  downtime Providing  support  to  the  ship’s  overall  mission In addition, you will also earn the confidence and support of your subordinates and the confidence and support of your seniors. ELECTROMAGNETIC INTERFERENCE  (EMI) EMI  is  an  electromagnetic  or  electrostatic disturbance  that  causes  electronic  equipment  to malfunction  or  to  produce  undesirable  responses  or conditions  that  do  not  meet  the  requirements  of interference tests. The dramatic increase in the types of electronic and electrical equipment since the beginning of World War II has brought about a problem that was given  little  consideration  in  previous  years-EMI.  EMI has become a problem because naval ships and aircraft now  contain  a  large  number  of  complex,  sensitive devices that are not always compatible with one another. As  an  ETl  or  ETC,  you  must  be  aware  of  the problems  caused  by  EMI  and  of  the  solutions  to  these problems.  No  magic  is  involved  in  reducing  or eliminating  EMI;  instead,  problems  are  resolved  by using  everyday,  commonsense  approaches  to  main- taining  equipment. SOURCES OF EMI There   are   three   types   (or   sources)   of electromagnetic interference: natural, inherent, and man-made. Natural  EMI Natural interference is caused by natural events, such  as  snow  storms,  electrical  storms,  rain  particles, and   solar   radiation.   This   type   of   interference   is commonly  called  static  or  atmospheric  noise.  It  can cause problems with rf communications and older data links between shore, ship, and air; however, it does not cause  many  problems  with  modern  digital  data equipment. Inherent EMI Inherent  interference  is  noise  within  a  piece  of electronic equipment, caused by thermal agitation of electrons flowing through circuit resistance. (This noise is usually noticed as the background noise heard in a radio receiver when it is tuned to a frequency between stations.) Man-Made EMI Man-made  EMI  is  produced  by  a  number  of different classes of electrical and electronic equipment. They  include,  but  are  not  limited  to:  transmitters, welders,  power  lines,  motors  and  generators,  lighting, engines  and  igniters,  and  electrical  controllers.  These devices  can  cause  severe  EMI,  which  can  degrade  the operation  of  shipboard  or  shorebased  data  processing equipment. The  discussion  of  EMI  will  be  directed  to  the recognition and elimination of the man-made EMI that you are apt to encounter ashore or afloat. TYPES OF EMI EMI can be classified by its spectrum distribution. EMI  can  be  either  narrowband  or  broadband interference.   These   terms   refer   to   the   frequency spectrum the interference covers. 8-3