OK I am weird, as a 3 year old (1954) I'd swipe my father's WWII MX-991/U flashlight. This is the standard right angle headed unit. I'd hide in closets, under the sink, under beds, in the small room the water heater sat in (under the stairs) and enjoy the light in the dark.
Dad was frustrated, "D" cells weren't horribly expensive, but he grew tired of having to keep a supply. Mom took the view point "At least he's not using candles."
A friend of Dad's worked for GE and gifted our family with early NiCad cells and a charger. Dad bought me my very own MX-991/U and I'd sit in the closet and listen to my "Boys Rocket Crystal Radio."
My maternal grandfather gave me a very old Prango 2 "D" cell flashlight with a patent date of Sept 28, 1915.
This unit uses a small silver plated "parabolic" reflector with a large glass lens.
Thus began my collection of flashlights.....a collection continues to grow, I've never met a flashlight I didn't like.
All of this is of historic interest and perhaps offers a view into my somewhat odd psyche, but what on earth does it have to do with Electronics 101.
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I could go into the vibrator powered electroluminescent light my dad built for me, or how my uncle replaced the vibrator with a pair of germanium power transistors, or how I made my first LED flashlight, it used red and green LEDs and either or both could be enabled, but I won't.
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[And for you with dirty minds....
https://en.wikipedia.org/wiki/Vibrator_(electronic)]
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Your portable electronic gear operates from batteries, unless you have a hand held generator or can operate off PV cells in direct sunlight.
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A friend gave me an interesting book. This book is almost mandatory for those of us who operate equipment from batteries
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Batteries in a Portable World: A Handbook on Rechargeable Batteries for Non-Engineers, Fourth Edition?
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It is available at Amazon (and at the ARRL), it is a bit expensive at about $30.
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I still distrust secondary (rechargeable) lithium batteries, but they are a factor of modern life and, unless I wish to give up my cellphone, laptop PC, portable equipment, I have no choice but to learn to live with the !@#% things.
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The book starts out with the basics of batteries and might appear too basic for a serious hobbyist, but it gets down to brass tacks with reasonably detailed information on many different types of batteries, their strengths and weaknesses. And all batteries have both.
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