This is the sound of a slide projector showing reversal film, or "diafilm" as it is also called.
A rectangular plastic box with slides is inserted into a rail on the side of the projector and as it slides down operated by a remote it pushes in the slide so it is projected on a canvas and then out again. So it works until you either run out of slides or it gets stuck. The projectors themselves look very different depending on manufacturer, the year it was made and what purpose it was built for. This particular example is from the 1960's or 70's and is made for home use.
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Erik Pålsson</div>
CC BY 3.0
<a rel="nofollow" class="external free" href="http://www.soundsofchanges.eu/sound/reversal-film-slide-projector">http://www.soundsofchanges.eu/sound/reversal-film-slide-projector</a><br><bdo lang="en" dir="ltr"><a href="//commons.wikimedia.org/wiki/Commons:YouTube_files" title="Commons:YouTube files">YouTube</a>: <a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=XwK-benrmQc"><bdi lang="">Reversal film projector.</bdi></a> – View/save archived versions on <a rel="nofollow" class="external text" href="https://web.archive.org/web/*/https://www.youtube.com/watch?v=XwK-benrmQc">archive.org</a> and <a rel="nofollow" class="external text" href="https://archive.today/https://www.youtube.com/watch?v=XwK-benrmQc">archive.today</a></bdo>