Standy engine indicators Aural warning Upper DU Lower DU Warning & cautions Engine primary displays Engine secondary or status display or maintenance display Discrete caution & warning lights R computer L computer Display switching Maintenance panel Display select panel Other system discretes FCC MCDP TMC interface FEC interface FMC interface RAD Altitude interface ADC interface Engine sensors N$_{1}$  Oil press N$_{2}$  Oil quantity N$_{3}$  Oil temperature EPR Vibration EGT FF System sensors Hydraulic quantity & press ADC hydraulic system temperature Control surface positions Electical system: volts amps freq Generator drive temperature ECS temps APU EGT. RPM Brake temperature Data buses L orem ipsum Figure 10-124.  Schematic of an engine indicating and crew alerting system (EICAS).  preference and the systems installed.  [Figure 10-128]  EFIS  provide for annunciation of advisory and warning messages  as part of its flight control and monitoring capabilities, as  previously described. Usually, the primary display unit is  designated as the location to display annunciations. Most aircraft include annunciator lights that illuminate  when an event demanding attention occurs. These use the  aforementioned colors in a variety of presentations. Individual  lights near the associated cockpit instrument or a collective  display of lights for various systems in a central location are  common. Words label each light or are part of the light itself  to identify any problem quickly and plainly. On complex aircraft, the status of numerous systems and  components must be known and maintained. Centralized  warning systems have been developed to annunciate critical  messages concerning a multitude of systems and components  in a simplified, organized manner. Often, this will be done  by locating a single annunciator panel somewhere on the  instrument panel. These analog aircraft warning systems may  look different in various aircraft and depend on manufacturer  Master caution lights are used to draw the attention of the  crew to a critical situation in addition to an annunciator that  describes the problem. These master caution lights are centrally  wired and illuminate whenever any of the participating  systems or components require attention. Once notified, the  pilot may cancel the master caution, but a dedicated system  or component annunciator light stays illuminated until the  situation that caused the warning is rectified. Cancelling resets  the master caution lights to warn of a subsequent fault event  even before the initial fault is corrected.  [Figure 10-129] 10-76