They do "exist", in the literal sense of the word. You can see a picture of one on the wikipedia page about it. http://en.wikipedia.org/wiki/Television_licensin

They do "exist", in the literal sense of the word. You can see a picture of one on the wikipedia page about it. http://en.wikipedia.org/wiki/Television_licensing_in_the_United_Kingdom#Detection_technology http://en.wikipedia.org/wiki/Television_licensing_in_the_Uni... However, they have never been used for enforcing TV licensing. They are entirely a publicity stunt / a myth put about by the BBC to scare people into buying a license.