The history of clear electronic devices in prisons

Seeing a video on Techmoan about "prison tech," I thought it was going to be about toilet hooch, shivs, tattoo guns, and the like. But this was something I never knew about: That prison electronics used to (still do?) have to be all-clear and the some of the features are disabled or hobbled.

I was also unaware of the fact that prisons were the main places keeping the cassette business alive long after it largely died out elsewhere. The US prison system didn't allow CDs because they were afraid the discs would get weaponized.

Image: YouTube