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This audio tape cartridge format was developed and introduced by Collins Radio in 1959, and at the same year it was introduced as a radio industry standard at the National Association of Broadcaster's (NAB) 1959 annual show. The cartridge originated in a design created by inventor George Eash from Toledo, and he had already in 1954 named his creation to Fidelipac. But he was not the first who had gotten the idea of an endless tape loop wound on a single wheel. Before him, Bernard Cousino, two years previously accomplished the same thing. Perhaps their idea had been influenced by a film cassette system where there also was an endless loop on a single spool of 8 mm moving film.
At the beginning the NAB Carts were limited to mono single-track audio, later, however, it was updated for stereo sound capability. The tape inside the cassette was a quarter-inch-wide (6.3 mm) analog recording tape The standard tape speed used on this cart standard was 7.5 ips (19,05 cm/sec), however, some machines could be set to use other speeds, such as 3.75 or 15 ips. Along with the audio track(s) the mono and stereo versions also had a separate inaudible cue track for the 1 kHz cue tone which automatically triggered the playback to stop mode, then setting the cassette cued and prepared for next instant start of the same recorded clip. The automatic cue function could also be used for relay start of another player and it was possible to arrange for a chain of players to start, one after the other. Some cart machines also offered an option for use of a secondary tone which was used to automatically switch to fast forward through the leftover length of tape when the recorded material was ended.
There were three sizes of Fidelipac carts available. The
commonly used for broadcasting purposes was the small 4-inch-wide with
a maximum playing time of 10 minutes at 7.5 ips. The next was the 6-inch-wide
model for holding longer programs of up to 20 minutes. The largest size
was the 8-inch-wide for playing times of up to 30 minutes. However, these
two larger models were hardly never used for any other purposes than for
background music applications where the tape speed usually was 3 3/4"
for longer playing times.
Before the cart machines were introduced, the practice for
playing recorded spots involved use of either reel to reel tapes or pre-recorded
vinyl discs. A recording of KLIF, Dallas Texas, give us a recall of how
the noisy crackly discs could sound in a broadcast at the beginning of
the sixties :
Two months after the above broadcast, the Swedish offshore station Radio Nord, with their initial broadcast on March 8, 1961 from the Baltic Sea outside Stockholm, Sweden, became the first broadcast company in the world to use the Spotmaster 500 as their standard machine for jingles and commercials. Radio Nord could start from square one producing their own jingles and commercials in their own studios, unlike the American radio stations which were so related to other partners within the broadcast industry where all involved had to undergo a total change from one industry standard to a completely new.
Unlike the later consumer-marketed 8-track cartridge developed later in 1964 by Bill Lear which had the pinch roller integrated in the cartridge
The nab cart cassette was very similar to the consumer-marketed Stereo-8 cassettes, often named as the eight-track cartridge, eight-track tape, or simply eight-track. This car stereo related standard was introduced in 1964 by Bill Lear as an American competitor to the European Compact Cassette (CC) introduced by Philips in 1963. The Stereo-8 standard was developed by a consortium where the largest companies were Ampex, Ford Motor Company, Motorola, and the RCA Victor Records Company.
Unlike most other tape recording standards the tape wasn't running from one reel to another. Instead they used only one single reel containing a continuous endless loop of 1/4-inch recording tape specifically prepared so that the tape were able to slip out from its inner round of the tape spool. On the back side of the magnetic tape, opposite to the magnetic layer, there were a surface of graphite as a dry lubricant making the tape able to easily slip out with very low friction. To make this possible it was also important that the tape was wound very lightly "airy" tensed on the spool . This, however didn't have to mean that the tape would slack inside the cassette because the tape around the hub had a lower linear velocity than the tape at the outside of the reel, so the tape layers would slip very lightly past each other.
When playback was started, the tape was lightly pulled out from the center of the spool and then it passed by the opening holes at one end of the cartridge where the magnetic head is "looking in through the window" in contact with the tape and the tape forwardly passes by the pinch roller / capstan and then the tape is wound back onto the outside of the spool. The spool was freewheeling - its rotation was driven only by the tape going out and then returning to the spool, and the only parts driving all of this was the pinch roller and the capstan. It was a very uncomplicated tape recorder construction depending on very few moving parts. The only disadvantage was the lack of fast winding abilities; it was technically impossible to rewind the tape, and the only way to make fast forward were by just speeding up the motor in playback mode while cutting off the audio.