I remember a photo from WW II time, no idea where to find one now, of the Europe underground (French maybe) where the guy was pedaling a bike-chain powered generator or magneto and the gal was sending shortwave code. The light on her face indicated they were hiding to do it. Not sure what the red cape means unless we’ll have to hide from the man to message again soon?
Note that the generator is driven off the small sprocket end to give it plenty of speed. They might have been using an automobile generator which would have most likely been 6 volt.