Detection Display
Filtered Mob Detectors will display what type of mob they are looking for while the player is near the block.
Detection Settings
Detectors can be set to detect within a variable range; Mob Detectors can be set to only detect one type of mob
Mob Detector Recipe
The default recipe for Mob Detectors requires red nether bricks, redstone, spider eyes, nether quartz, and a slimeball.