Search this site for AU5ES and you will find a few threads regarding this switch. You will find the opinions of people are much more knowledgable than I am and/or have this switch installed and are happy with its performance.
I bought one today at Ace hardware for $85 because my float switch has not been reliable over the last two weeks over which we received about 15" of rain. Also, it was the last one they had, so if I decided to install it, I didn't want to go back and find it was sold out. I, too, am on this site to get more information about the switch. You can also read reviews on Amazon.
One thing I do not like about this switch (and others here agree) is it uses a timer. You set the sensor to the level where you want the pump to come on. When the water drops below this level, the timer starts. You set the timer for the duration required for the level to drop to a point above the suction inlet of the pump. After the duration is complete, the pumps shuts off. The problem I see is this concept does not accommodate different flow rates into the sump. That could cause the pump to cycle more often than necessary during/after a heavy rain storm, or stay on too long, thereby allowing air to get in, when there has been just a light rain.
I did a search ad found these
http://www.washerwatcher.com/Hi_Lo_Controller.htm with dual sensors at comparable price but I have know idea of their quality. I also found other choices at Grainger.com but they were $120, or more.
