Notices they're not using the old fax machines (7)

I believe the answer is:

posters

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'notices' is the definition.
('poster' can be a synonym of 'notice')

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for posters that I've seen before include "Bills or placards on walls" , "Public placards" , "Contributors to forum" , "Placards, notices" .)

I've seen this clue in the Evening Standard.

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