Four window comparators and an oscillator
Quad Comparator consists of four window comparators and a triangle oscillator. The window comparators allow users to set two voltage levels, one high and one low, and whenever the incoming signal is between these two levels the output will go high (LED is on, ~10V output), outside of those levels it will be low (LED is off, 0V). The four inputs of this module are normalled sequentially, so the four comparators can be used together, separately, or in any combination.
Info from ModularGrid