The hfsignals WireUp instructions for power into the rig at the top of   http://www.hfsignals.com/index.php/ubitx-wire-up/
have a symbol that looks like headphones.
Some have mistaken it for a fuse, that's definitely the wrong position for a fuse.
The label on that symbol says "On/Off", so we can assume it's a power switch.

Here's an old post showing how I wired mine up:
    https://groups.io/g/BITX20/message/53016