<p>Controls on receiving side of Mufax Courier fax machine by Muirhead &amp; Co. (1975).
</p>
The button provided 1-bit instant feedback about an unsatisfactory image received.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/30661871@N03">Richard Ash</a>
CC BY-SA 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/30661871@N03/45807842994/">IMG_5596</a>