One feature is a Next18 DCC socket. This is mounted on a plastic motherboard above the motor toward the rear of the unit, where the Next18 socket points downward. I used a Digitrax DN167n18 decoder.
The best way to get to this is to loosen the rear nut and screw that hold the two halves of the chassis together enough to lift the rear of the plastic motherboard up, remove the Next18 dummy plug, and insert the Next18 decoder. There is barely enough room for trhe decoder to fit between the socket and the chassis, but it does fit.
Once I appllied power to the loco, I noticed there is an extra set of LEDs at the front 9of the chassis. These will allow the number boards to be lit and controlled separately from the headlight. The headlight is controlled via the usual F0:
With a DCC-only Next18 decoder, the number boards can be lit with F1: I don't know what function controls this on a sound-equipped loco.I don;t believe these locos have flywheels, or if they do, there is very little momentum effect. However, setting CV 3 acceleration momentum to 2 and CV 4 deceleration momentum to 2 will mimic a flywheel effect. The loco has a 5-pole skew-wound armature and operates very slowly and smoothly.
Unfortunately, as seems to be the case with recent Atlas N locos, there's no documentation in the box. Users need to figure out shell removal and decoder install for themselves and intuit the headlight-number board functionss. (The shell comes off by spreading the sides outward with small screwdrivers or toothpicks.)
An exploded diagram of the loco showing the location of the Next18 socket would have been very helpful; it isn't immediately clear.