[nickcw]

That brings back fond memories of my first employer in the early 90s.

They used to rent a single scan line (VBI) of the TV broadcast to use as a data transmission method encoded the same way Teletext was. IIRC you could fit 45 bytes in a single scan line, with 50 per second that gives you a nationwide data broadcast capability of something like 18 kbit/s. We had a 19,200 bits/second leased line to send the data.

That scan line was really really expensive I seem to remember! If your TV wasn't quite adjusted properly you could see the data scan lines at the top of the screen as flickering white dots and lines which was fun.

The data got sent to financial institutions for real time stock feeds and nationwide networks of shops.

I never worked on the code for that part of the business though - I worked on the replacement system which ran via satellite with much more bandwidth at much lower cost.

Eventually the internet killed that too :-)

[BoxOfRain]

I love learning about pre-internet ways of transferring data on the back of other things. Another cool example is that the UK is only shutting down its longwave AM radio service this month (as opposed to decades ago) because the carrier is phase-modulated with data telling older electric meters to switch over. For years this was the only reason such an antiquated radio system stayed alive.

[mschuster91]

In Munich (Germany), a lot of the displays at bus and tram stations get their data via a side leg on the FM radio broadcast of local station B5 aktuell [1]. More details are here [2], apparently it's called "Axentia iBus FM/DARC".

[1] https://www.mikrocontroller.net/topic/232846

[2] https://apollo.open-resource.org/mission:log:2014:08:08:darc...

[reaperducer]

I love learning about pre-internet ways of transferring data on the back of other things.

I once worked for a radio station that made 90% of its revenue from carrying data feeds on subcarriers, and not from main music programs.

Because of the geographic location and size of the signal, it was a vital link between two major cities before planting fiber optic lines became cheap.

[Scoundreller]

I’m looking forward to cell phones un-shackling themselves from telecom oligopolies through a mix of repurposed satellite uplink and where available: some FM spectrum downlink utilization.

Just stream me the weather, traffic, text msgs & some news stories that a TTS can read out to me.

Won’t work well for streaming a video but for most of us generally on wifi except out-of-doors, I can live with it.

[reaperducer]

Just stream me the weather, traffic, text msgs & some news stories that a TTS can read out to me.

SiriusXM is half way there. It supplies weather and traffic as a data service.

I knew about traffic from way back when the service was new, and found out Sirius Marine Weather a few years ago, but recently rented a car that also had Sirius-delivered weather and traffic alerts.

It was very useful as I was deeply off the grid (no radio stations at all during the day and AM skywave only at night), and the car alerted me to nearby lightning and thunderstorms that I couldn't see because of the terrain.

[ErroneousBosh]

Up here in the north of Scotland the various council water and drainage departments often had to send data from remote data loggers (high tech stuff in the early 80s). Some of them would transmit a little ping of data every few seconds and if it heard a reply it would send several bursts of data quickly, using meteor scatter[1] to get it back to the receiving station hundreds of miles away.

All gone now, it's all 4G.

A few hours drive north of me is Mormond Hill, formerly the site of one part of the North Atlantic Radio System[2]. This used tropospheric scattering and huge dish aerials to communicate radar data down to RAF Fylingdales. There's not much up there now. There were various BT microwave links for offshore oil installations and assorted UHF and VHF links up, but the masts are pretty bare now.

[1] https://en.wikipedia.org/wiki/Meteor_burst_communications

[2] https://en.wikipedia.org/wiki/North_Atlantic_Radio_System

[IrishJourno]

You should check out the Media Archeology Lab, they are very interested in alternate networks of all types! https://www.mediaarchaeologylab.com/

[cf100clunk]

> I love learning about pre-internet ways of transferring data on the back of other things

See Minitel from France and Telidon from Canada as other examples of data systems riding on analogue TV and/or POTS telephone systems.

[ErroneousBosh]

> If your TV wasn't quite adjusted properly you could see the data scan lines at the top of the screen as flickering white dots and lines which was fun.

There was a stock fault on BRC 1400 series valve TVs where a resistor in the brightness network would drift high in value and cause uncontrollable bright flyback lines in the upper half of the screen, and you could see those wriggly dotty crawlies ;-) I can't remember the component number - I think I last replaced one when I was 15 or 16, they were the teenage bedroom hand-me-down set of choice in the 80s, absolutely scads of them about in all sizes - but I can still picture in my mind's eye exactly where on the board it is, 220kΩ, red red yellow.

All long gone now, I expect.

If you find one do not re-cap it - the capacitors will be fine. They always are, there aren't any tantalums in it. Instead pay attention to everything above about 200kΩ and find out which ones are now closer to 1 meg!

[reaperducer]

They used to rent a single scan line (VBI) of the TV broadcast to use as a data transmission method

In the days before cable TV was widespread, there were over-the-air devices to give you a "TV Guide" page, like your cable/satellite service does now.

It was a tiny gray box about the size of a VHS tape, with a cute antenna sticking out of the top.

It constantly received program listing data through scan line data services, and filtered the listing by your ZIP Code. It displayed its TV Guide page on channel 3 or 4, and passed through the rest of the spectrum from your antenna. Because of this, it could even switch channels for you.

It cost something like $40, and after that was a totally free service, with no advertisements.

I'm pretty sure I got mine at Radio Shack, so it's probably listed in the catalogs around 1994 or so.