A wind-up radio

Read the following text and fill in the gaps with a word from the boxes below:

A (1) __________ radio (or windup radio) is a radio that is (2) __________ by human muscle power rather than batteries or the electrical grid. In the most common arrangement, an internal (3) __________ generator is run by a mainspring, which is wound by a hand crank on the case. Turning the crank winds the (4) __________, and a full winding will allow several hours of (5) __________. Clockwork (6) __________ have now been replaced by batteries charged by hand-crank generators in commercial crank-powered radios.

Like other self-powered (7) __________, clockwork radios were intended for camping, emergencies and for use in areas of the world where there is no (8) __________ and replacement batteries are hard to obtain, such as in developing (9) __________ or remote settlements. They are also (10) __________ where a radio is not used on a regular basis and batteries would deteriorate, such as at a vacation house or cabin.

Newer crank-powered radios that do not use clockwork, but are designed for emergency, use often included flashlights, blinking emergency lights, and emergency sirens. They also may include multiple alternate power sources such as conventional or rechargeable (11)__________, auto cigarette lighter (12)__________, and solar cells.

Radios powered by handcranked generators are not new, but their market was previously seen as limited to emergency or military (13)__________. The modern clockwork radio was (14) __________ and patented in 1991 by British (15) __________ Trevor Baylis as a response to the AIDS crisis. He envisioned it as a radio for use by poor people in developing countries without access to batteries. In 1996 he co-founded Baygen Power Industries (now Freeplay Energy PLC), which produced the first commercial (16) __________. The key to its design was the use of a constant velocity spring to (17) __________ the potential energy.