Tandy Radio Shack Computer Cassette Recorder (TRS CCR) Introduction

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PART 1: Introduction

Between about 1977 to 1988, the (relatively) inexpensive minicomputers (home/office personal computers) needed a way to store digital information (computer programs and data) in an affordable way. As a practical solution, minicomputers borrowed the existing format of the audio cassette tape (which had been around for over a decade already, since about 1963). These were “shoe-box” sized devices that were essentially a more compact and portable version of reel-to-reel tapes if the 1950s.

Disk drives were available for the earliest minicomputers, but were still difficult to produce and thus much more expensive (both the disk drives and the disk themselves were roughly 5-10X times the cost of a tape recorder and cassettes — for example, $50 tape recorder and $1 tape versus $500 disk drive and $5 disks). In addition, early cassettes could also store more than the early 5.25″ disk drives (roughly 200KB capacity tape on a 60min reel tape compared to early 160KB formatted disks). By the mid-1980s disk drives were much more common and affordable, but use of cassette tape was still popular until the end of that 1980s decade (except in high end servers, where special high speed and high capacity tapes were used for system backup purposes — which remained popular until the early 2000s).

While a regular/typical audio cassette recorder could be used, one technical issue was in the volume used to record (save) information vs. volume used to recall (load) information. There were varying convention used (e.g. AUX vs MIC), and varying quality amongst cassette recorder manufacturers (e.g. on exactly what Volume Level 1 through 10 meant, in terms of precise intensity or gain). Plus as a recorder was used for other purposes, the volume knob might be adjusted for different situations (such as recording in a stadium vs. recording an interview at a table, as “regular” cassette recorders were often used for voice dictation and not directly intended for recording digital data). One might save a program, only to find the volume wasn’t sufficient to later load that program on Computer A or a different Computer B (that used different cassette recorder equipment).

One disadvantage of cassette recording for digital-data is there is no real “error checking” to ensure the recording was made correctly. The only way to verify a SAVE would be to reload the data, which meant clearing the original memory contents of the system. If the LOAD failed, the content was altogether lost. Thus a lot of printing was done to make hard-copy of source code listings, and a lot of time spent re-typing those listings.

Chuck Peddle, the designer of the Commodore PET (1977), was aware of this issue of inconsistency. So for the Commodore line, they developed a Datassette, with a specific cable design and no volume knob. This wasn’t done on the Apple computers, which just used the “regular audio” jacks — which was more versatile, but also more inconsistent (and thus frustrating to end-users, having to learn by trial and error on a workflow that suited whichever recorder device they had available).

BELOW: Example of the Commodore Datasette, where the tape-lid is more fully enclosed (no dust gaps), the tape sits in a nice-fit tray and is not ejected abruptly, and uses Commodores proprietary interface cable. The data encoding mechanism was also more favorable to digital data, making the Commodore tape solution generally more reliable than other contemporary solutions.

Tandy took a sort of hybrid approach between Commodore and Apple. Like Commodore, they used a “special” cable, with a 5-pin DIN on the PC side, then exposed regular audio jacks at the other end (whereas for Commodore, the cable was “hard-fixed” to the Datassette). Tandy offered a set of (rebranded) “computer”-oriented cassette recorders, that effectively standardized what type of recording device should be used for their systems. But the cable gave the flexibility to also use “non-standard” cassette recording devices, for end-users savvy enough to set them up.

So in the Tandy-domain, an end-user might use an existing tape cassette recorder solution, and it “might” work (like the Apple experience). But if they used a Tandy-branded cassette recorder, the thorough documentation helped ensure a more consistent working solution “out of the box.” However, unlike Commodore’s Datasette’s (unmodified), the Tandy cassette recorders could also be used for regular audio/dictation recording and playback.

NOTE: To clarify, this is not to say there was anything particularly special about the Tandy CCR series of cassette recorder (relative to a “normal” audio cassette recorder). But the Datassette and Tandy devices did ensure sufficient quality of circuits to be suitable for digital-data recording (of programs and data). This is in contrast to lesser quality devices (like used in some consumer toys), but also in contrast to modern devices that may have more “digital-interference” (like noise-reduction filters) that aren’t suitable or necessary for the cassette save/load routines embedded into ROMs. The Datassette likely was hard-wired to a specific volume, but the Tandy recorders had “ALC” circuits (Automatic Level Control) – while a feature not unique to the Tandy models, it is a feature that helped ensure consistency and reliability of using their devices for purposes of saving digital-data.

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