Minecraft wiki entry for Observer, associated text: 1 Obtaining
1.1 Breaking
1.2 Crafting
2 Usage
2.1 Behavior
2.2 Limitations
2.3 Note Blocks
3 Sounds
4 Data values
4.1 ID
4.2 Block states
5 History
6 Issues
7 Trivia
8 Gallery
9 See also
10 References