Heat tape
If you’re not watching Apple’s phenomenal show Silo, your missing out on some of the best TV from what we will later regard as the beforetimes.
Two recurring themes in the first season are heat tape and its various grades and applications and obsolete technology. WE DO THOSE SAME THEMES RIGHT HERE and also we drop episodes more frequently.
Heat tape is usually something that protects from heat, generates heat, or holds it in. Thermal tape, on the other hand, is often a paper or plastic tape that changes appearance upon heating, or which releases dye onto some other substrate. It’s very common in receipt printers at point of sale terminals. Old fax machines that used curly paper worked the same way.
I like to believe the stuff works by magic, mostly so I don’t have to think about the crazy chemistry of how it actually does work and what that means for the millions of people who touch that stuff.
This kind of thermal tape is the inspiration for the Denbridge paper and hydroterms in Merrimac, though darkened by reaction with platinum typehead instead of by heat. As implausible as the hydroterm is, thermal terminals actually were a thing for a while. TI practically invented the genre in the 1970s with the Silent 700 — a portable teletype device with a built-in thermal printer. Some models in the series also had rechargeable batteries and a built-in 300 baud modem with acoustic couplers. It’s easy to say that these machines fill a gap between the portable typewriter and the Tandy TRS-80 Model 100 portable computer but it diminishes all three to have the 700 as just an in-between. Each represented an exciting technology in their own right — and each continues to be used. Something that kept the TI in the pink years after it was discontinued was that it was useful as a portable printer before that product category really even existed.
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Anyhow, there was no linear family tree from typewriter to keyboard. Electric typewriters were adapted into some of the first interactive consoles for computers but computer technology fed back into improving typewriters in their own right. IBM’s model B typewriter was a popular early candidate for consolification. IBM developed several computer-enhanced versions of their Selectric line. Although some of these Selectrics could be used as a mainframe console, most of these enhancements centered on making core task of typewriting and typesetting easier. By 1984, the typing was on the wall for the Selectric mechanism — obsoleted by the fast modern Daisy Wheel and fierce competition from Xerox and others. IBM’s next and final generation of typewriters, the WheelWriter, would be based on that mechanism. By 1984, typewriter adaptation in support of computers meant that IBM introduced a WheelPrinter alongside the Writer — video computer consoles were themselves completely adequate and affordable for interactive use except for the preparation of ‘letter quality’ documents. IBM made a parallel adapter for the WheelWriter to allow an existing WheelWriter to operate as a PC printer.
Where the computer-enhanced Selectrics and WheelWriters were premium products, the fierce competition sparked by the daisy wheel mechanism meant that computers could now be used to do what they do best — make things cheaper. Electronic keyboards and lightweight type carriages eliminated hundreds of grams and hundreds of moving pieces from a traditional typewriter. In technology, competition is often fiercest just before a product disappears entirely. The tide driving down price is the same tide that is making orders of magnitude more capability affordable in some new product category that doesn’t even have a name yet. CD players didn’t leave much room in the market for laser turntables.
What was even cheaper than a daisy wheel? The bitmap dot-matrix head. Although dot matrix quality was low, that could be easily solved without further computing power if the individual pins could be mechanically compressed to increase resolution. That’s exactly what thermal printers are. The wires are finer because they don’t need to move. They heat the paper directly, or heat a transfer ribbon from which dye sublimes onto the paper or they boil some ink through a micro-fluidic jet onto the page. Thermal inkjet became just inkjet.
These mechanisms were light, cheap, and they took less power than every other printing technology. Suddenly, the cheapest typewriter was computerized by default and almost intrinsically portable.
Japan’s Canon started as a camera and lens company that grew naturally into optical xerographic reproduction and facsimile fields and they grew from there into the cutthroat document preparation and office automation markets. Already a leader in portable photocopiers, Canon introduced both the TypeStar portable thermal typewriter line and the BJ-80 thermal BubbleJet inkjet printer in 1985 (trailing HP’s ThinkJet by a year) — two years after the introduction of the TRS-80 model 100 portable computer.
My TypeStar 7, pictured above, uses Hitachi 6801-alike with a few hundred bytes of on-board ram, a kilobyte of external RAM, and a few tens of kilobytes of ROM to run the show. A key advantage of the daisy wheel was that alternate typefaces were just a new type wheel away. For the thermal TypeStar, the equivalent of a new typewheel was a ROM cartridge with a new typeface. Several cartridges were available for my model. Mine has one other feature that was not common among compact electronic typewriters — a serial port. Canon supplied very little documentation about this port (Alex Dueppen furnished the official schematic, one of the best sources of information). Does it work as a printer? As a terminal? I don’t know yet.
For some help, we can reach back to one of our 24k machines — the SciSys Kasparov chess computer. The notes for a related SciSys machine, the Leonardo, had an available connection cable whose documentation references connection directly to a TypeStar 7. The Leonardo, BTW, is also built on a Hitachi 6801-type processor.
The SciSys documentation suggests that the typewriter connects as a write-only printer device at TTL levels. It should be easy enough to connect this to an Arduino. For that matter, the TypeStar could probably be used with the TRS-80 model 100 as the letter-sized portable printer Tandy never released.
By the way, the TI model 707 terminal, released at around the same time as the TypeStar, is based on the obscure TMS 7041 microcontroller. Is the TMS-7000 series microcontroller perhaps a spiritual ancestor of the MSP 430 we profiled in 24k #22? I don’t know! TI was long a consumer of their own parts and many parts were made exclusively for other TI products, so their full family tree is sometimes hard to understand.