EST wired up and ready to go, designed for applications where the main locomotive is supported by an APU, avoid waste of main engine's power.
EST Main Panel and Display Panel

The Engine Shutdown Timer (EST) is a timing device, designed to shut down a locomotive’s engine after it has spent a certain amount of time in idle.  

This timeframe can be set to 15, 30, 45, or 60 minutes, according to your preferences.  After main engine is shut down, the EST will wait an additional 2 minutes before turning engine lights off. 

Typically used in the absence of an AESS system.

EST/APU Partnership

Designed for applications where the main locomotive is supported by an Auxiliary Power Unit, the EST works with the APU to avoid waste of the main engine’s power.  This is accomplished by shutting down the main engine and allowing the APU to monitor functions (such as keeping the engine lubricated and the battery on a trickle charge).

Product Details

The EST consists of a Main Panel and a Display Panel. 
The display panel has two buttons, APU START and HDLT (Headlight) RESET.
APU START is for conveniently starting the APU from the cab of the main engine.
HDLT RESET is a timer that will count down while the main engine is in idle, during the last 30 seconds of which, the beeper will sound.
The beeper will also sound 5 short times if the APU START button is pressed and there is a problem starting the APU.