Forces open the Valves for Anti-ice for wings/tail, basically telling the plane I don't care if you aren't detecting ICE, I want it on anyway

On the ERJ it has little things on the sides of the Nose that vibrate, and when it picks up ice it stops vibrating, which tells the a/c it is icing up. The EMB-145XR has additional Clear Ice detection which is kind of nice.

If I remember on the SAAB it was certain Temps and visible Moisture we would just manually turn the ice on. In the ERJ you always know when the ICE Protections just turned on because you feel the pressure in your ears