It is a single contact (push to make contact) switch grounding the control line to the servo's (with an additional 5k resistor over the switch to the Dynon system can detect a broken wire failure). Look in the installation manual and the users manual for the term disconnect or disconnect button, there is a lot of description. The disconnect button directly interfaces with the servo's of the autopilot and it immediately disengages them (it doesn't just remove the power that is a very crude way of controlling the servo's). It provides a direct deactivation of the autopilot function and if installed in the stick it is much quicker to use, when the autopilot does something that the pilot doesn't like. The button actually does more as it also activates the autopilot function, for a description of the complete functionality and the interaction with the autopilot function read the users manual. (sorry).