Vintage Computing: Saving data to an audio device

Back when the early days of per­son­al com­put­ing, you did your work on your com­puter and either prin­ted out the fin­ished work, or stored it to work on later. Early on, cas­sette tapes were the stor­age medi­um of choice as they cas­sette tape record­ers were com­monly avail­able, and reas­on­ably afford­able. Some com­puter sys­tem did have disk drives, but they were more expensive.

Though cas­sette tape was the default meth­od of sav­ing your work, the pro­cess was fussy, was very hands-on, and worked like this on the NEC PC-8201a:

• plug the tape deck into the com­puter using the appro­pri­ate cables
• on the com­puter, move the curs­or to the file you wanted to save
• press the Save key [f‑2]
• type the file name you wanted the file to be saved as when writ­ten to the cas­sette. Make sure you make note of the file name you enter, exactly, as you’ll need that if you want to load that file back from the cassette
• ensure you have a tape in the cas­sette record­er and the Record and Play but­tons are pressed.
• answer [y] to the ‘Ready?’ question.

The com­puter will then con­trol the cas­sette deck using the Remote con­trol port through the cas­sette cable. It will start the deck, write the file name to the tape, then write the file data to the tape and stop when the file has been written.

Mission accomplished! Good work!

Whew! A lot of things to do to save a file. Now, to get the file back off the tape and back into the com­puter. Read­ing (or Load­ing) a file from tape is pretty much the reverse — you provide the appro­pri­ate file name, and when the com­puter sees it as it plays through all the files on the tape, it will load the reques­ted file, ignor­ing all the oth­ers. Read on to see how it worked with mod­ern equipment.

How it works?

Files were stored sequen­tially on the cas­sette — the com­puter could­n’t auto­mat­ic­ally fast-for­ward to the next file. If you were crafty and had a good ear, or used the tape index counter on the record­er and wrote down the ‘loc­a­tion’ of each file as you saved it to tape, you could skip ahead to the appro­pri­ate counter index number.

Fairly straight­for­ward.

Now let’s do it with modern equipment.

If, like me, you don’t have a work­ing vin­tage cas­sette record­er, you’ll have to use a com­puter or digit­al audio recorder.

I happened to have a digit­al micro­phone with a line in jack.

Depend­ing on the device you use, you will have to turn off or dis­able any sound fil­ters (low-pass, auto rec. level, etc) as we want to record the pure sound from the computer.

Mod­ern digit­al record­ers gen­er­ally record in ste­reo through the line-in port, so you’ll need a ste­reo split­ter cable between the cas­sette deck and the record­ing device. That will sep­ar­ate the left and right chan­nels, and give them their own jack. Then plug one of those sep­ar­ated jacks into the com­puter data cas­sette cable.  One plug on the data cable will be for Data In, anoth­er for Data Out. Depend­ing on how the cable was wired, the jack that may mean Data In to the the record­ing device, OR data in to the com­puter. Give it a test, one will work, the oth­er won’t 🙂

In my case, the file will be recor­ded as a digit­al sound file (WAV format) on a mini SD card, which can then be read by any com­puter as an audio file. You won’t be able to read the spe­cif­ic data until you load that audio file back into the appro­pri­ate computer.

Since the digit­al micro­phone does­n’t have a Remote func­tion, I had to manu­ally time the start­ing and stop­ping of the recording.

A bonus fea­ture of the micro­phone, it had a head­phone jack so I could mon­it­or the sound com­ing from the com­puter as it was start­ing, send­ing, and end­ing the process.

Here’s how it worked:

• same pro­cess for record­ing as above, up to the point of press­ing ‘y’ to start the cas­sette record­er by the remote
• at this point, your com­puter is wait­ing for the ‘y’, start record­ing on the digit­al device. You’ll hear the com­puter send­ing a sol­id tone.
• once the record­er is record­ing, then type ‘y’ on the key­board, and listen to the save pro­cess if you’re mon­it­or­ing through the micro­phone head­phone jack.
• the com­puter can­’t turn off the record­ing device when the file has fin­ished unless it too has a remote con­nec­tion (my micro­phone did­n’t) so you’ll have to watch the screen on the NEC to determ­ine when the sav­ing is done, or listen for the quiet ‘click’ of the relay inside the NEC — this relay is what is con­trolling the remote con­trol cable.

Now that you’ve safely got a copy of your mas­ter­piece (in my case, an uned­ited ver­sion of this blog post) on the SD card, you can move it to your com­puter, save it to your hard drive, email it to friends, or even link to it in a blog post!

To load your saved mas­ter­piece back into the com­puter, as men­tioned pre­vi­ously, the pro­cess is simple:

• select the file on the digit­al play­back device
• press the ‘Load’ but­ton and enter the file name used when you saved the file to the device ori­gin­ally (it’s good to keep notes)
• then when promp­ted, enter the file name to save the incom­ing file as. Remem­ber to append the appro­pri­ate suf­fix (.DO, .BA, etc) to the file name or you’ll get an error.
• When promp­ted on the com­puter with ‘Ready?’, press play on your digit­al play­back device
• then type ‘y’ to start the com­puter read­ing the incom­ing data file

The com­puter will tell you when it finds a file by dis­play­ing ‘Found file­name’. If ‘file­name’ matches what you’d entered when you told the com­puter to Load ‘file­name’, the the file will be saved to your com­puter. Oth­er­wise, the com­puter will ignore that file and listen for the next one.

Back in the day

So yeah, a very clunky manu­al pro­ced­ure with a few obvi­ous fail points.

But it’s neat to play around with and dis­cov­er that you can still read and write text and BASIC files to audio, just like they did in the lat­ter part of the last cen­tury — if you can con­vince your mod­ern equip­ment to work like the old-timey stuff does.