Annunciator Dim Test Unit (ADU)
The Annunciator Dim/Test Unit (ADU) simplifies the engineering task of installing aircraft system annunciators. It provides a dedicated source of adjustable dimming, power, and testing for both pilot and copilot annunciators in one compact unit.
The Bright / Dim and Test mode functions are designed to ease installation and are triggered by either +28VDC or ground logic.
Instructions for Continued Airworthiness, Here.