Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Built Environment (hierarchy name)
4. Single Built Works (hierarchy name)
5. single built works (built environment)
6. [single built works by specific type]
7. [single built works by function]
8. communications structures

Anotations

Scope note:

Concrete structures of various forms, usually including a concrete dish linked to microphones, acting as early warning systems to detect and transmit the sound of incoming zeppelins; installed along the English coast facing Europe during the early 20th century.