Welcome to the only page on the web where you can see the Famous Philco Mystery Control in action.
The Philco Mystery Control was the world's first wireless remote control. Introduced by Philco in 1938 for the 1939 model year, it was able to change stations, raise and lower volume, and turn the radio off (but not on) from anywhere in the room up to 25 feet away, all without any wires connecting it to the radio. It was the latest techno-whiz-bang of its day. But it only lasted until 1942. It would be 1956 before anyone would try remote control again (Zenith's famous Space Command).
There's not many of these devices left today but they are truly marvelous little gems of mechanical and electronic ingenuity. Actually seeing one work gives you some appreciation of what folks were able to do over 70 years ago without computers, back in the days before IC's, wi-fi, and Bluetooth.
Here are some short movies that illustrate the Mystery Control in action, controlling a 1939 Philco Model 39-116 console radio. Each movie is an mpeg file less than a minute long. The Mystery Control is operated by turning a dial similar to a rotary telephone dial. It has 10 positions, one for each of eight different stations, one to raise the volume, and one to lower the volume.
Volume is controlled by pressing down on the finger-stop before the dial finishes its return to the home position. This drops a pin down in the way of the wiper arm preventing it from returning all the way and holding the transmitter on as long as you press down. That in turn drives the volume control motor in the desired direction.
In each movie, you first see station 1 being dialed, then stations 5, 7, and 8, as well as the volume being changed. The radio automatically mutes the volume while the station changing is in progress.
Note that clicking the links below just asks your browser to open the file. Your browser must have the appropriate helper app installed to know how to play the mpeg. Microsoft Windows Media Player seems to work well enough. Quicktime is also able to play these. I'm sure there are others too.
This site should now work with Internet Explorer 8 as well as Firefox. I have heard it does not work with IE7. I don't know why.
Watch the Mystery Control transmitter being dialed (and hear the results). (2.52 MB)
This is what the rotary station switch under the chassis is doing when you spin the dial. The right-most section section selects the station coil, the middle section activates the appropriate pilot lamp and the left-most section selects the antenna padder for that station..(3.55MB)
Here's the volume up/down function (dialed with the LOUD and SOFT keys). (1.09 MB)
See the Mystery Control pulser in action. The last two spins at the end command volume down and volume up, respectively. Note how the wiper arm is prevented from returning to the home position when you press down on the finger stop. That makes it come to rest on a contact which keeps the transmitter "keyed down". The volume control motor continues to run as long as it receives this signal. There is a clutch to prevent damage if you hold LOUD down too long. If you continue to hold SOFT down, eventually the set simply turns itself off.(3.58 MB)
Here's what the relays (under the cover in the receiver) do. The relay on the right is the holding relay; the one one the left is the stepping relay. The holding relay must pull in or nothing will happen even if the stepping relay activates.(3.01 MB)
This is the ratchet mechanism under the relays in action. There are several adjustments here that in all probability do not need to be touched. If your ratchet won't go, it's much more likely that the old lubrication on the station selecting switch has dried out and gummed up the works.(3.30 MB)
This is the 2A4G Thyratron firing. It flashes once for each pulse received. This tube normally has a metal shield over it but that was temporarily removed to make this video. (3.66 MB)
Mystery Control Service Notes
Back in 1939, Philco said that there were "no user serviceable parts" inside the Mystery Control or the box containing the equally mysterious relay assembly inside the radio. We beg to differ! And here's how to service them...
If you're lucky enough to own a Mystery Control and want to get it running, I strongly suggest you check out this page at The Philco Repair Bench. This is the definitive collection of general information, specs, history, schematics, and principles of operation available anywhere for the Mystery Control. It is an invaluable reference for the MC owner. For truly excellent coverage of all things Philco, be sure to take a look at www.philcoradio.com.
The radio's remote receiver must get fairly precise pulses from the Mystery Control. If it doesn't, it either won't activate at all or will operate erratically. The most common problem is a pulser running too slowly because the mechanism needs cleaning and lubrication.
