Hello all. I am trying to find a sensor (probably switch is a better word) that will output a HIGH or LOW depending if the water (say, in a tank) has reached a certain level. I first googled: pressure sensor, then pressure switch. I also stumbled upon water level sensors, and now I am kind of confused. I searched for some on amazon, this is what I found: https://www.amazon.com/Amico-Aquarium-Liquid-Sensor-Stainless/dp/B006Z9691O/ref=sr_1_5?ie=UTF8&qid=1390023344&sr=8-5&keywords=water+level+switch https://www.amazon.com/Amico-Liquid-Sensor-Horizontal-Switch/dp/B007Q85J7S/ref=pd_cp_hi_2 These contraptions don't make sense to me, I can only see two wires, GND and VIN, where is the output wire? Any help will be appreciated. Thanks.