Back-up display of N1, EGT, and N2 is provided by the Standby Engine Indicator (SEI) on the P1-3 panel.
Engine operating limits are indicated on overlimit placards mounted on the SEI face. Respective sensor signals are input directly to the SEI to assure display in the event the Engine Indication and Crew Alerting System (EICAS) display units or EICAS computers fail.
NOTE: The Standby Engine Indication operation makes it necessary to have either 28VDC aircraft power or the engine operate.
When the SEI switch is "ON", you will see the digital display whenever the SEI is powered. When the switch is in the "AUTO" position, you will see the digital display only when the EICAS has failed. The SEI can be tested using a screwdriver operated switch on the left side of the SEI.