My father in law grew up in the Denver area. His father made his living as a handyman, and one of his regular customers was Molly Brown (the Titanic survivor known as "The Unsinkable Molly Brown"). Every week he would go to her house to exchange her radio battery, then bring the old battery back to his workshop for charging.
replyFrom what I understand, the crank was used to ring the exchange's bell, not to reload the phone battery.
replyYes, in the old systems, you'd get about 90 volts AC down the line to ring the mechanical bell ringer. Once saw a guy nearly fall off a ladder, splicing phone lines with bare hands. He thought the relatively low voltage was safe enough, but then someone rang him in the middle of the job.
replyI know 30+ years ago as I kid I learned this in my parents basement as I was rigging something up.
replyIt is more the surprise, as if one is ignorant to this fact it is not expected at all.