It might not look much, but the Sony SRF-39FP pocket AM/FM radio is regarded as the audio player of choice in prisons across the United States.
The New Yorker has an excellent feature about the use of the radio in prison. Unlike many consumer electronic devices you'll see these days, the SRF-39FP has a transparent plastic body, which houses a single AA battery, a simple antenna made of copper wire and ferrite, and some simple AM/FM circuitry. So why's it so common in prisons? Simple:
Its clear housing is meant to prevent inmates from using it to smuggle contraband, and, at under thirty dollars, it is the most affordable Sony radio on the prison market... The SRF-39FP is the gold standard among prison radios in part because it runs on a single AA battery, and offers forty hours of listening time—longer than an iPod Classic. Digital models can require twice as many batteries, like the Sony SRF-M35FP, which runs on two AAAs. Federal inmates are particularly attuned to battery life because they are allowed to spend just three hundred and twenty dollars each month on commissary goods; more cash spent on batteries means less for snacks, stationery, clothing, and toiletries.
Clearly, owning and running a radio is particularly useful in prison, allowing inmates to listen to music and keep abreast of news. In fact, studies even show that in situations where privacy is eroded—like prison—radio is one of the most popular modes of maintaining a private self. The SRF-39FP, then, is a vital resource for prisoners across the US. Go read the full feature over on the New Yorker, though, because it's incredibly interesting. [New Yorker]