Perhaps the earliest example of this was Felix the Cat, used by early mechanical television stations in the late 1920s to claim their part of the broadcast band

Perhaps the earliest example of this was Felix the Cat, used by early mechanical television stations in the late 1920s to claim their part of the broadcast band [1]. They placed a wooden model of Felix on a turntable, trained a 120 line "flying spot" camera on it, and left it on. I read a contemporary account of watching an early televised prize fight which mentioned this as well, but I can't for the life of me find it anymore. [1]: http://framemaster.tripod.com/Electronictv.html http://framemaster.tripod.com/Electronictv.html