Editing 8-track cartridge (section)

=== Development===
[[File:Quad 8 Track (white background).jpg|thumb|A blank compatible Stereo-Quadraphonic 8-track cartridge]]
[[File:Unitape-8-track-recordimg-cartridge.jpg|thumb|Blank cartridges could be used to make recordings at home.]]

Inventor George Eash invented a design in 1953, called the [[Fidelipac|Fidelipac cartridge, also called the NAB cartridge]],<ref>{{cite magazine|url= https://books.google.com/books?id=BikEAAAAMBAJ&q=George+Eash+CARtridge+inventor+tells+how+it+was+born&pg=RA1-PA19 |title=George Eash CARtridge inventor tells how it was born |magazine=Billboard |date=3 March 1966 |volume=78 |issue=10 |access-date=26 January 2013 }}</ref> which would later be used in not only the Muntz [[Stereo-Pak]] but also in various monaural background music systems from the late 1960s to the early 1990s.

His inspiration came from one of the first products that used the [[endless tape cartridge]] technology, which was the Audio Vendor from a year earlier, an invention of [[Bernard Cousino]]. The tape is passed through an inner ring of loose tape reel, where the recording is stored, and looped back through the outer ring of the reel. Initially, this mechanism was to be implemented in a reel-to-reel audio tape recorder.

Later, Cousino developed a plastic case that could be mounted on some existing tape recorders. This cartridge was marketed by John Herbert Orr as Orrtronic Tapette. In this generation, the tape was wound with the magnetic coating facing the inside of the reel. Later cartridge types had the magnetic layer facing the outside of the reel, so it had to be played by a specially designed recorder. Once traction of the tape by capstan was added, users had the convenience of just pushing the cartridge into the recorder without having to thread the tape. These cassettes needed no internal space for the tape head slider because they accessed the tape from outside the cartridge.

Based on these new cassettes, George Eash developed the Fidelipac cartridge in 1954. [[PlayTape]] and the endless-loop compact cassettes for the announcement text of answering machines were made with this technique as well along with other similar but incompatible answering machine tapes. The original separate take-up reel got a platter laid under the supply reel to combine the two and the perforation around the edge of the reel for traction was removed. There was no rear winding reel inside such a cassette so rewinding was impossible. Previously, a similar technique was used to store [[Tefifon]] grooved-vinyl sonic tape in the Tefi cartridge but without the benefit of a reel due to the width being 16mm, over twice that of an 8-track and due to the thickness of the film at 3 mils (75μm).

Another similar technology was the LaBelle Tutor 16 which combined several endless loop technologies at once. A 35mm filmstrip was reduced to 16mm and loaded into an endless loop film cartridge similar to a Fisher Price Movie Viewer which used silent truncated versions of 16mm cartoons. The bottom of this cartridge acted as the top for the sound cartridge below it which was basically identical to an 8-track. The only difference was the recording was the same 2-track format as mono NAB carts at the same 3-3/4 IPS speed (9.5&nbsp;cm/s) as an 8-track with the program material on one track and the subsonic picture-change automation tone on the other track.

Films, both silent as well as sound, in 8mm as well as 16mm configurations and in optical as well as magnetic sound formats were also endless loops, used in everything from store end-cap sales tools, to on-the-road engineering instructions to early portable airline movies. Instead of having any part of the mechanism located inside the cartridge, the only part located there was a 45-degree mirror to reflect the light through the film and onto either the internal frosted screen or an external screen by way of flipping another mirror in to redirect the picture.