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Did you mean "Clacks"? Or was it an attempt to point to https://fr.wikipedia.org/wiki/Sudac_air_service which has no English version AFAIK?

https://parisianfields.com/2018/03/25/a-question-of-time/

Fascinating but mislabeled. This is about the Paris Pneumatic Post, or underground tube message system.

Actually, the Pneumatic Post actually served to keep time in Paris in the late 19th century.

The Paris Observatory utilized the pneumatic system to distribute the official time across the city by sending pneumatic pulses at predetermined times, which would then be used to adjust the clocks as needed.

Video reference here: https://www.youtube.com/watch?v=gol_p2aWrJg

Video reference: https://www.youtube.com/watch?v=gol_p2aWrJg

The Underground Clocks of Paris