At 11:53 PM 12/8/2015, wulfman wrote: >The "carts" were 4 track tapes.
They were not. They were either 2 track for mono or 3 track for stereo, and they were physically different from, and not interchangeable with, consumer tape cartridges. Radio carts were introduced in, IIRC, the early 1960s (I would have to check my broadcast equipment catalogs) and predate the Lear 8 track cartridges. Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA http://plymouthcolony.net/starcityeng/index.html
