What core mechanical component did Baird's early system rely upon for both scanning and display?

Answer

The Nipkow disk

Baird's mechanical system was based on the Nipkow disk, a spinning disk featuring a spiral pattern of holes, which Paul Nipkow had patented decades earlier. Baird used this disk for scanning the image at the transmitter and recreating it at the receiver.

What core mechanical component did Baird's early system rely upon for both scanning and display?
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