No it's not an 8-track tape. Cart Machines played endless-loop tape cartridges also called carts or Fidelipacs. These were historically used to hold commercials, jingles, announcements and promos of all sorts. Audio was recorded in mono usually and 1 KHz cue tones were recorded on a separate track. This second track indicated to the playback deck where to stop rewinding or playing.
The tape format was introduced to the (NAB)National Association of Broadcasters by Collins Radio in 1959 with it's first model, the Spotmaster. later versions of the Cart machine had stereo capability, additional cueing tones and even timers.
For the past twenty years, broadcasters have used cart machines as a standard playback device for in-house audio. Only the infiltration and growth of digital audio in radio studios really put an end to it. The cart machine was reliable and functional. Before cart machines, commercials were played back via reel to reel machines. The DJ had to thread the tape, then manually cue, and rewind the tape.
The cart machine solved these problems but brought along it’s own issues. No two brands of cart are made exactly the same. The small differences caused by the manufacturing processes prevented exact alignment of the cart machine to more than one cart! The irregularities of each cart usually cause phase problems between the left and right channels in stereo models, and in severe cases a miss-cue.. As the lifetime of the Cart wore on, it also became clear that we all were recycling our carts for far too long. Old carts sounded worse than a beat up 78 rpm platter. But at least I never had to reboot a cart machine during my show. More here and here.