Popping off the final guard, the greased gear is free to go. The Echo's spinning input wheel is similar to that of the Nest Thermostat, but is implemented completely differently.

The Echo uses a gearing system and encoder to track movement of the outer wheel, whereas the Nest uses an optical sensor to watch the outer ring spin by.

Around the edge of the wheel, we find the microphones responsible for hearing your commands (six on the perimeter, plus one in the center of the board), and LEDs used to indicate Alexa's acknowledgement.