Instrument 01 / Binary-coded decimal
Binary clock
How to read it: each column is one decimal digit. Add the lit values -- 8, 4, 2, and 1 -- to recover that digit.
Why this clock exists
NIST added a binary-coded-decimal time code to radio station WWVB in 1965, encoding each decimal number with four bits. This face performs the same small translation in public: every familiar digit is opened into weighted choices of 8, 4, 2, and 1. The lit cells suggest that machine-readable time is still our ordinary time, carried through a different agreement about symbols.
NIST history of WWVB