An AstroVac SR-50 central vacuum power unit installed in a large house. This is one of two units installed there.
<ul><li><a href="//commons.wikimedia.org/wiki/File:Central_vacuum_system.png" title="File:Central vacuum system.png">Central_vacuum_system.png</a>: <a href="//commons.wikimedia.org/wiki/User:PleaseStand" title="User:PleaseStand">PleaseStand</a></li>
<li>derivative work: <a href="//commons.wikimedia.org/wiki/User:PleaseStand" title="User:PleaseStand"><i>Please</i><b>Stand</b></a> <sup><a href="//commons.wikimedia.org/wiki/User_talk:PleaseStand" title="User talk:PleaseStand">(talk)</a></sup></li></ul>
CC BY 3.0
<ul><li><a href="//commons.wikimedia.org/wiki/File:Central_vacuum_system.png" title="File:Central vacuum system.png">Central_vacuum_system.png</a></li></ul>