TM 10-3610-202-14 Section VII.  RADIO INTERFERENCE SUPPRESSION 4-14. General Methods Used to Attain Proper Suppression. a. Essentially, suppression is attained by provide a low  resistance  path  to  ground  for  stray  currents.    The methods  used  include  shielding  the  ignition  and  high- frequency   wires,   grounding   the   frame   with   bonding straps, and using capacitors and resistors. b. The term interference as used herein applies to electrical   disturbances   in   the   radio   frequency   range which are generated by the special warfare printing plant and  which  may  interfere  with  the  proper  operation  of radio  receivers  or  other  electronic  equipment,  or  may enable the enemy to locate the equipment. c. The    term    interference    suppression    as    used herein  applies  to  the  methods  as  used  to  eliminate  or effectively  reduce  radio  interference  generated  by  the special warfare printing plant. d. The   items   of   equipment   which   make   up   the editorial and photomechanical unit of the special warfare printing    plant    have    been    chosen    to    meet    military requirements   for   radio   interference   suppression.      All electric motors are either of the brushless type or, as in the Varityper composing machine, have built-in suppression  features.    The  shelter  construction  is  such that  radio  interference  from  the  fluorescent  lighting  or other equipment is greatly reduced. 4-15.  Interference Suppression Components. The equipment installed within the shelter system which  could  cause  radio  interference  includes  motors installed in the platemaker, composing machine, and air conditioner and the fluorescent lighting used for shelter and light table illumination. a. Motor    Suppression.        Motor    suppression    is achieved through the use of capacitors and appropriate shielding.  Reference should be made to the applicable technical    publication    for    the    type    and    location    of equipment radio suppression components. b. Fluorescent  Lighting  Suppression.    Fluorescent lamps   contain   mercury   vapor   at   low   pressure.      This vapor is ionized by a flow of electrons in the tube.  The deionization   that   follows   causes   ultraviolet   radiation which excites the internal phosphor coating causing it to radiate and give off light.  The electron stream, or arc, in the    tube    is    a    source    of    radio    interference.        The interference may be radiated from the lamp or the power leads,  or  transmitted  by  conduction  through  a  common power    system.        For    systems    that    use    starters,    a capacitor  may  be  placed  across  the  starter  terminals. Systems without starters usually have built-in capacitors mounted in the ballast, or current limiting device.  It is impossible to suppress direct radiation from fluorescent lamps since shielding defeats the purpose for which the lamps are used. 4-16.  Replacement of Suppression Components. Refer  to  the  applicable  technical  publication  for removal   and   installation   of   suppression   components used    in    the    platemaker,    composing    machine,    air conditioning system and light table. 4-17. Testing of Radio Interference Suppression Components. Test capacitors for leaks and shorts on a capacitor tester; replace defective capacitors.  If test equipment is not available and interference is indicated, isolate the cause of interference by the trial and error method of replacing each capacitor in turn until the cause is located and eliminated. Section VIII.  MAINTENANCE OF CABINETS AND STORAGE COMPARTMENTS 4-18.  File Cabinet Assembly. The   file   cabinet   assembly   is   a   ten-drawer   unit installed   at   the   left-hand   shelter   wall   adjacent   to   the door. The upper drawers are provided with compartments   for   storage   of   smaller   items.      Label holders   are   attached   to   each   to   provide   for   content identi fication labels.  An upper and lower locking clip permits insertion of a vertical locking bar to prevent movement of the drawer during shipment and storage (See fig.  4- 7.) The cabinet, which is of welded metal construction is used for storage of artist historic files and supplies. 4-23