Controls on sending side of Mufax Courier fax machine by Muirhead &amp; Co. (1975). Upper light provides a 1-bit instant feedback from the far end if an unsatisfactory image was received over the analogue phone network.
<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@N03/46531588941/">IMG_5595</a>