VCC ---/\/\/\/---|TO MCU|--- SWITCH ----|GND
VCC --- SWITCH ---|TO MCU|---/\/\/\/----|GND
not to say it couldnt be something different, but those two above would be 95% of the designs out there.
So depending on how much resistance between a contact and ground and a contact and power, you can tell if it is directly connected (<< 1ohm) or going through a current limit resistor (probably > 100ohms, closer to 1kohm, or 10kohm).
The Fusion Brain is like the first option. There is always power to the + pin. The - pin is connected and disconnected as told by the computer. So when you say "turn on" it is grounding a pin, which would ground the output, set the signal low, and trigger an event.