Mackenzie Multi-Program Repeater, Model APR-20, with 10 decks.
No where were the "top 40" radio battles more exciting than in Dallas. Gordon McLendon owned KLIF, while his arch rival, John Box, ran KBOX. Having two capable and innovative competitors in one market made for some exciting radio. These Dallas radio battles produced some memorable and exceptional talent over the years.
From this news air check, you can hear that KBOX grabbed the "news with music" format pioneered by Bud Connell and made good use of their "MacKenzie". Try to find this kind of excitement on radio these days.
KBOX used a 10 channel Mackenzie, while most stations opted for the basic 5 channel. It was located behind the jock, out of his reach, as the endless loop cartridges were not changed. It's interesting to note that the first use of the Mackenzie Repeater was by CBS to add "technically augmented" audience reactions (laugh tracks) to their live television comedy shows. The Mackenzie pre-dated the ubiquitous "tape cartridge" by several years.
KBOX was housed in an attractive brick building on a large, well landscaped lot in those days, but the control rooms were small, a shambles of simplicity, junky and ill equipped, belying their bigger than life over the air image. It was the talent that made radio great in those days, not technology, save perhaps for the famous "Mackenzie".