A window detector circuit, also called window comparator circuit or dual edge limit detector circuits is used to determine whether an unknown input is between two precise reference threshold voltages. It employs two comparators to detect over-voltage or under-voltage.
Each single comparator detects the common input voltage against one of two reference voltages. Outputs behind a logic gate like AND detect the input as in range of the so-called "window" between upper and lower reference.
https://en.wikipedia.org/wiki/Window_detector
