[Chas]

The Mystery controls work below broadcast band the remote sends a series of pulses keyed by the telephone dial. There is a type 30 tube and a fil/plate battery inside the filament lights very quickly at the time of dialing. The receiver for the low frequency uses the loop antenna in the bottom of the radio, a thyratron tube to key a step transfer relay and a two phase motor to turn the appropriate mechanism.

The receiver and the transmitter have to be on the same frequency and are identified by a number, FWIR there are just a few frequencies. I also believe the Mystery box frequency or the radio can be tuned to match if they don't already.

Most problems are dried out bipolar AC cap at the motor as well as the usually paper caps in the low frequency receiver. I think the range is about 30ft and one wall in between...

There are ample documents online for this feature so it is no "Mystery" at all...

Be aware the dial and its escutcheon are made of Tenite and may be irreparable warped.

Get it working, impress your friends and neighbors, old cool stuff!

GL

Chas