The IBM Selectric and Its Mechanical Digital-to-Analog Converter (2010) [video] | Hacker News Reader

The IBM Selectric and Its Mechanical Digital-to-Analog Converter (2010) [video]

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Many, many years later I used a modified Selectric hooked up to a cassette-tape based storage system to typeset a yearbook for a student society. The system worked on a line-by-line basis, comparable to the 'ed' editor (later bowdlerised and bastardised by Microsoft into 'edlin'). You would type a line, make corrections using the backspace button on the storage system, then press carriage return to store the line on tape.

We managed to enter the entire book - which was quite long and wordy - onto a stack of cassette tapes. Once this was done, all that was left was to run those cassettes through the storage system, having it print the result on good quality paper which would be cut into page-sized bits to be glued on templates.

...and then the motor in the Selectric burned out. I managed to find a replacement motor and got the thing working just in time to run the text through. Adjusting the tilt and rotation cables was quite an effort, initially the text would dance up and down the line, characters half-printed and all.

The end result was quite good, actually. The Selectric offered proportional spacing and the film ribbon have excellent contrast.

Had I not used the Selectric I would have used runoff on a PDP-11. The latter was deemed to cumbersome to my co-authors (who were less computer-minded than I was, this being an agricultural university, and thus could not stand the half-second wait between pressing the 'backspace' key on the VT52 and the cursor responding...). They did not like the 'near letter quality' print from my Panasonic KXP-1081 either, for which I can not blame them anymore (but did back then).

The Selectric is an elegant mechanism. Typewheel typewriters go back to the late 19th century; if you want a typewheel machine, Blickensderfer machines are available on eBay for a few hundred dollars. IBM had electric typewriters, including ones that could communicate, decades before the Selectric.

The Selectric has a mechanism with a modest number of moving parts, and rotational joints rather than sliding elements. This keeps the noise down and reduces the need for lubrication. That's what made this device suitable for general office use. Teletype machines, which do roughly the same job, are much louder and need considerable lubrication. (I restore pre-WWII Teletypes as a hobby, so I know.)

There's a variant of the Selectric for computer interfacing, the IBM 2741.

Here's an appendix he made with some more details about the mechanical DAC:

https://www.youtube.com/watch?v=G_SC7oWL78A&list=UU2bkHVIDjX...

Bill Hammack is a national treasure. I can't highly enough recommend subscribing to his video series: https://www.youtube.com/user/engineerguyvideo/videos

I have this idea for an art project: Cross-connect two Selectrics with a long cable so typing on one keyboard outputs on the other and vise versa. They two people could chat with each other. (Analog point-to-point teletype?)

My dad thought this was so cool back in the 60s, he actually dismantled a Selectric to determine if he could use it as an input keyboard for a desktop electromechanical computing device he worked on at Xerox.

Selectrics were used as I/O devices on machines like the IBM 1130.

Yes, in 1973-74 I used to submit college FORTRAN programs to an IBM 360 sixty miles away via an IBM 2741 Selectric console http://en.wikipedia.org/wiki/IBM_2741 that was connected to an IBM modem device/leased line. We used a line-oriented editor of a remote job entry system to create virtual 80-column decks of cards ("jobs") that included the job control language as well as the programs themselves. In the second semester we exchanged the Selectric's regular type ball for one with APL symbols (the 2741's keys had both regular and APL symbols), and used IBM's time-shared 360 APL system via the 2741. This was considerably more fun than FORTRAN because of a) the immediate interactivity and b) APL's amazingly compact notation. APL one-liners were like nothing before or since in computer languages.

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