On the main alarm panel, there are two GROUND INDICATOR  LAMPS  (fig.  1-27)  to  indicate  the presence of a ground in the alarm system. All shipboard alarm panels and remote sensors are electrically isolated from the ship’s ground. The  only  exception  is  the ground fault detector, which is connected to ground for ground  monitoring.    If one of both lamps light, you should  have  the  alarm  SWBD  and  its  remote  sensors The AUDIBLE SILENCE CONTROL is a two-position switch  that  permits  silencing  (VISUAL  POSITION)  the audible alarm on the main panel. The ALARM lamp on the main panel is lighted when the AUDIBLE SILENCE CONTROL is placed in the VISUAL position, and the system is in an alarm condition. The lower half of the alarm panel (fig. 1-27) holds the alarm modules that are connected through the alarm panel to the remote sensors. On the panel depicted, there are only five alarm modules used while the rest is blanked  off  with  covers.  Should  additional  remote sensors be installed at a later date, a new alarm module is plugged into the lower panel for each sensor installed. Each  alarm  module  includes  a  center-divided  lighted display.  Either  half  can  independently  display  a  steady red light, a flashing red light, or no light, depending upon the circuit logic. The six possible combinations of alarm module  lights  and  the  appropriate  audible  alarm  are shown in figure 1-28. Located on the lower half of each alarm module is a four-way position switch that allows you  to  place  the  individual  alarm  module  in  the following   modes:       NORMAL. This is the normal operation mode. With the sensor contacts open, the upper indicator lamp in the module will be on steady while the lower lamp is off. If an alarm condition occurs, the sensor contacts will close; the upper lamp will then flash while the lower lamp remains off and an alarm command from the module actuates a tone generator, producing a wailing alarm. If the sensor loop is open-circuited, with the selector switch in the normal position, the alarm module signals a supervisory failure; in this case, the upper lamp will be off while the lower lamp will be steadily on, and the tone generator will come on, producing a pulsating alarm. STANDBY. This   is   the   position   for acknowledging  an  alarm.  If  the  selector  switch  is moved from the normal to the standby position during an  alarm  condition,  both  the  upper  and  lower  indicator lamps will be steadily on and the audible alarm will be silenced. When the alarm condition is cleared with the selector  switch  in  the  stand-by  position,  the  lower  lamp changes to a flashing mode and the upper lamp goes out. Also, a command is fed to the tone generator, producing a  pulsating  alarm.  This  pulsating  alarm  signal  informs the operator that the selector switch should be returned to the normal position. C U T O U T .  With  the  selector  switch  in  the CUTOUT position, the upper lamp is out while the lower lamp is steadily on. In this position, power is removed from the sensor loop to facilitate maintenance. TEST. This selector switch position simulates an alarm condition. The upper indicator lamp will flash while the lower lamp will remain off. A wailing alarm is  produced. Your proper response to the coolant alarm SWBD could  mean  the  difference  between  a  small  service problem or the markings of a much larger disaster. For example,  the  COOLANT  SUPPLY  EXPANSION TANK  LOW-LEVEL  alarm  module  senses  a  low coolant  level  in  the  expansion  tank,  immediate  action must be taken. If the tank should empty, the pump will draw air into the lines and force it throughout the secondary   cooling   system. This   would   require additional  maintenance  to  correct  the  problem. WAVEGUIDE  FLOODING An improperly maintained liquid cooling system can cause a major disaster in your waveguide system, if it is liquid cooled. The damage caused by waveguide flooding can easily run into thousands of dollars and include the expenditure of hundreds of manhours by ship’s  force. Various components of high-powered radars, such as dummy loads, load isolators, and circulators are cooled  by  the  use  of  liquid  coolant.  These  components use a ceramic plug (or disk) in a water-cooled load. Transmitted rf energy passes through the plug and is absorbed as heat by liquid coolant flowing through the load. The plug acts as a window for rf energy, and at the same  time,  forms  a  watertight  seal  between  the waveguide and the coolant jacket of the load. Particles of oxidation and dirt from a dirty coolant system can buildup on the coolant side of the ceramic plug. The buildup can create an impedance mismatch or hot spot. This condition can generate an arc, which carbonizes the ceramic plug so that coolant can leak through or around the carbonized plug. Since a nominal 80-psig pressure differential exists between the coolant in the load and air in the waveguide, coolant  can  flow  from  the  water  load  into  the waveguide,  resulting  in  waveguide  flooding.  Once  the 1-24