Mixed in with some other gear I’m servicing, I found this old Music Minder power box. It’s not all that obvious what it’s for at first glance!

Some digging around found an explanation in the June 1958 issue of Popular Mechanics:

Neat! Let’s see in more detail:

It’s a pretty unassuming box. Plug the turntable into one, the hifi into the other, and set the switch to “Automatic”. Manual appears to leave the Hi-Fi Equipment plug always-on, leaving the power to be controlled by the unit itself.

The bottom is crimped on, but easily removed by bending the tabs back up.

Pretty simple inside! A couple of sockets, and a relay whose actuator coil appears to be in series with the record player plug. While the record player is running on “automatic” mode, current would flow and close the relay, powering the Hi-Fi Equipment socket. When the record player switches off at the end of the record, the relay would un-latch and kill power to the amplifier. Simple, but effective! That looks like a burn spot, though, right by the coil.

Indeed, there’s a charred strip in the relay’s winding where the coil burnt up. Maybe someone plugged a high-power amplifier into the record player socket, and it couldn’t take the excess current? Either way, this interesting hi-fi accessory appears to be a display piece only, but it’s still fun to see!