The young person shown here is about 80 years old, and was probably never kidnapped, thanks the the alarm shown in the December 1939 issue of Popular Mechanics.

The child’s safety was the result of the photocell operated burglar alarm, manufactured by the National Company (yes, the same company that made radio equipment) of Malden, Mass. The light source, photocell, and amplifier were located in a single unit, and made a beam reflected off a mirror. The beam could be up to 30 feet long, and any break operated a relay which could activate a chime, bell, or light.