Minecraft wiki entry for Redstone_Comparator, associated text: 1 Obtaining
1.1 Natural generation
1.2 Breaking
1.3 Crafting
2 Usage
2.1 Maintain signal strength
2.2 Compare signal strength
2.3 Subtract signal strength
2.4 Measure block state
2.4.1 Fullness of containers
2.4.2 Miscellaneous
3 Sounds
3.1 Generic
3.2 Unique
4 Data values
4.1 ID
4.2 Block states
4.3 Block data
5 Video
6 History
6.1 Redstone comparator "items"
6.1.1 Appearances
6.1.1.1 Unpowered Comparator
6.1.1.2 Powered Comparator
6.1.2 Names
6.1.2.1 Unpowered Comparator
6.1.2.2 Powered Comparator
7 Issues
8 Trivia
9 References