Memory

Katie, who is 11, was helping me in the workshop today. She told me how some of her class been in trouble for filming the teachers covertly. Of course I told her how, in 1965, I'd made a sound recording of our maths teacher, with the class deliberately winding him up just to make it more fun. I then found myself trying to explain about reel-to-reel tape recorders. I could see that Katie just couldn't grasp the concept. Finally she asked, "But how much memory did it have?"

Bill

Reply to
Bill Wright
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I don't know whether to laugh or cry...

It's slightly scary that there's people wandering around who regard the CD as pre-historic. I feel old.

Reply to
Adrian

I regard not only CD as pre-historic but DVD and Blu-Ray[1] too. It's not that that makes me feel old, just the effects of old age creeping up on me.

[1] or BD if you prefer.
Reply to
Johny B Good

In message , Bill Wright writes

You sound like an older father, although perhaps Katie is your Granddaughter. My son has just turned 13, and I'll be 62 shortly. I do try to complete his education, explaining what life was like pre mobiles, computers, game machines, tablets etc. All sorts of stuff - our first black and white TV, with two channels and very little TV for children, our first phone tied to the wall with a cable, our 'wireless', first fridge all of which arrived in my lifetime. His Grandma (and mine) operating the mangle every Monday, deliveries of milk, bread, paraffin, no central heating, clockwork toys, my first wind up gramophone, 45s, 78s, LPs, reel to reel, my first CD, cassette tapes, Walkman, Commodore 64, Atari etc. Things that arrived during my lifetime, yet were gone by his. Pirate radio. Trying to explain that there was no Radio 1, no local stations, no TOTP, no YouTube. Just David Jacobs :-) Highlights of the week including Ready Steady Go, Thank Your Lucky Stars (Oi'll give it foive!), Juke Box Jury.

The impact of Elvis and The Beatles. Luckily, he hears me playing golden oldies, is used to us having an open fire, drives my Minor in the garden, eats with us at the table in the dining room and plays with my tinplate trains. He even enjoys traditional board games at Christmas. He doesn't like Meccano, though.

The other side of the coin, of course, is that he keeps me up to date with what his generation loves. Funny thing is, although he and his friends will spend hours in front of a screen, they also do so much that I did, 50 years ago. Out on their bikes, messing about by the river, building dens and dams. What really delighted me, when he first started school, and understood humour, was the jokes. He and his friends were laughing at *exactly* the same jokes as amused me at that age. He also adored the same cartoons, like Huck Hound and Yogi Bear. The difference was we saw them once a week on B&W TV - he watched them constantly, in colour, via DVD. Oh well ...

Reply to
News

Adrian wrote in news:ljjtbl$6au$2 @speranza.aioe.org:

With the old devices we all had some inkling of how they worked and if we were to survive some sort of massive global disaster we would have known enough about the principles to get these devices back in use. Nowadays the ability to make or even understand common devices is in the hands of very few people. Who remembers using a pin and some rolled up card to listen to a 78rpm record?

Reply to
DerbyBorn

Well, terms for storage have changed over the years I suppose. I once worked out that on a ZX Spectrum, about 5 minutes of cassette tape equalled

32Kbits at 1200 baud, but of course the special loaders games used pushed the baude rate up so the loading was much faster, and of course less reliable.

Then of course reel to reel could have several speeds, and the difference was in frequency responce and noise performance as it was analogue. If you can explain the difference between analogue storage and digital storage it might make the penny drop.

Did you know that the Gallileo probe to Jupiter had a tape storage system on board for use to send the stored data to earth. It started to stick with age so they had to spool it back and forwards a bit each time theywanted to use it. More modern space vehicles use Flash ram of course, but these have issues that tweak their bits when they get hit by a cosmic ray.

More useless information from the web. Brian

Reply to
Brian Gaff

Yes indeed, and I still play them and Vinyl as well. I'm in the market for a good quality reel to reel deck as well. Brian

Reply to
Brian Gaff

I loved meccano. I used some the other month to make a door closer for my porch. Incidentally, Meccano made me a phonograph together with some bits of tin and a cardboard horn. The cylinder was made from baco foil and of course had a clunk every rotation, but did actually work surprisingly well to demonstrate the principals, though speed variability was a bit of an issue, as was recording time.. grin. Brian

Reply to
Brian Gaff

Presumably old age is having its normal affect on hearing and sight so you don't notice how crap downloads and/or streaming are compared to CD or Blu-Ray (or even DVD come to that). B-)

Reply to
Dave Liquorice

Its memory is the tape. Struggling to remember, but ISTR a tape lasts 30 mins at 7.5"/sec. The frequency response at 7.5"/sec looks to have been up to 15kHz. In thinking of this digitally, that's a sampling rate of 30kHz as per Nyquist. I've no idea what the dynamic range is, but let's guess it's at least 8 bits worth (it's probably more). That works out at

30kbytes/sec, or 60kbytes/sec for two-channel (stereo). So for a 30 min tape, that's just over 100Mbytes.

Today, that would be mpeg compressed on a personal player, so perhaps just 50Mbytes (won't get as good compression as modern digital recordings, because original data is already at a reduced resolution).

So best answer is that the tape player has no memory, but each tape corresponds to perhaps a 50Mbyte SD card today (way smaller than anything you can buy today).

Reply to
Andrew Gabriel

A work colleague was recently telling how her grandson (4) tries to "swipe" books like an iPad when they read ...

10 Years ago my son had to do a little project (IIRC it was on castles). Quite naturally, he laid his work out like a web page, with "back" and "home" buttons drawn around the edge.
Reply to
Jethro_uk

Not bad for a 25 year old. :-)

Reply to
Martin

When my daughter was fairly young (4 ish perhaps) she had mastered the video and DVD player and could watch various films / programs / compilation tapes over and over[1] - quite often the same one several times a day for weeks at a time. She was sat with mum watching a broadcast of one of the Albert Campion series of shows... at the end said "again mummy, again!" It was then mum had to explain the whole concept of broadcast TV to her!

[1] Clangers, Bagpus, Ivor the Engine, The Trap Door etc, plus loads of classic Cartoons.
Reply to
John Rumm

Its one of the ways teachers can spot the less than skilful plagiariseation of web based stuff for homework - they still leave the hyper-links in ;-)

Reply to
John Rumm

ROFL too true!

Reply to
Martin

Wow! It's amazing that it could record time at all. Once you sort the issues out, you couldn't record a bit for me, could you? I'm sure it will come in useful in a few years time when I wish I had a bit more.

Reply to
Norman Wells

My estimate would be 30 minutes at 3 3/4 inches per second, mono, 10 kHz frequency response, signal to noise ratio 40dB.

That converts to 1800 seconds at 20 k samples per second. 40 dB would be about 8 bits, but 8 bit audio sounds rougher than tape, so I'd guess 10 or

10 bits x 20k x 1800 = 360 Mbits = 45 MBytes.

Has she ever seen a VHS cassette? They come out at 1000 times more.

3 hours, 2.5 MHz frequency response, 30 dB s/n, converts to

6 bits x 5000k x 10800 = 324 Gbits = 40 GBytes.

Reply to
Stephen

My very young niece was caught having out several coins into the floppy disk slot (or maybe zip drive slot) of a Mac G3 to 'make it work'

Reply to
The Natural Philosopher

What worries *me* is that many teenagers are of the opinion that downloads are better quality than CDs.

Even at my age, I can tell the difference, even on earbuds and small screens.

Reply to
John Williamson

Erm. That would depend on the length of the tape. Which in turn depends on the size of the spools and the tape thickness.

Chances are that a decent R2R will record above 15kHz at 7.5ips. Depends on the tape, heads, etc. Unlike LPCM there's not sharp cutoff.

Even a decent home machine like the old Tandberg 3000 would do 40 - 20k at

+/-2dB running at that speed. And could record higher frequencies provided they were're high level and you accepted a drop in output. The unweighted noise approached -60dBref and you could also record above ref for mid-frequency signals. And I'm sure there were better decks around.

Its likely to be more than 8bits worth, but again depends on the tape, deck, etc. And it isn't easy to estimate because the response and noise floors aren't flat in-band. Nor is the max signal level limited by an abrupt ceiling. Instead by a rise in distortion that depends on the details of the signal being recorded.

Plus, of course, a tendency later on the use Dolby level compansion which further complicates the issue. And ignoring the detail of if you are thinking of a full/half/quarter track for mono or stereo. I'm assuming the usual home machine width and format. :-)

So > 20kHz bandwidth and about 60dB range would be a closer guide, but probably still not give a really representitive value for some 'Mbytes' result.

Jim

Reply to
Jim Lesurf

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