We take remote controls for granted. For most of us, they've existed from the day they were born. We knew how to use them before we could even begin to fathom how they work. But really, they're magnificent devices.
Push a button on a little box, and you're able to shoot an invisible beam across a room and directly control another device. Now thanks to wi-fi, nearly any device capable of logging on to a network can become a remote. But the first real product to do this was the Philco Mystery Control, first introduced in 1939. Using RF waves to issue its commands and resembling a rotary phone without the handset, the Mystery Control also functioned like one.
According to Philco Repair Bench, controlling a radio was more or less identical to making a phone call, with each function mapped to a different area along the dial.
Dialing "Loud" and pressing down the finger stop (or volume control lever) makes the Mystery Control send a continuous RF signal to keep the volume control motor in the radio turning to the desired loudness. Releasing the finger stop will halt the volume change. Dialing "Soft" and pressing down the finger stop keeps the volume control motor in the radio turning to your desided level. If you continue holding the finger stop down the motor will eventually click off the power switch, turning off the radio. The radio cannot be remotely turned on since the control frequency receiver in the set is also off.
Measuring in at 6-inches by 8-inches by 4-inches, the Mystery Control was not the epitome of portable. And setting one of these things up was not at all easy (you had to dial in the right radio frequency by hand and had to avoid placing your radio by anything with a radiator). But I'm sure people were willing to overlook that, considering nothing like it had ever existed before. [Philco Repair Bench]