Retrotechtacular: How Television Worked In The 1950s

May 6, 2022 by Jenny List 29 Comments

Watching television today is a very different experience from that which our parents would have had at our age, where we have high-definition digital on-demand streaming services they had a small number of analogue channels serving linear scheduled broadcasting. A particular film coming on TV could be a major event that it was not uncommon for most of the population to have shared, and such simple things as a coffee advert could become part of our common cultural experience. Behind it all was a minor miracle of synchronised analogue technology taking the signal from studio to living room, and this is the subject of a 1952 Coronet film, Television: How It Works! Sit back and enjoy a trip into a much simpler world in the video below the break.

Filming a TV advert: 1950s housewife sells cooker — Production values for adverts had yet to reach their zenith in the 1950s.

After an introduction showing the cultural impact of TV in early-50s America there’s a basic intro to a cathode-ray tube, followed by something that may be less familiar to many readers, the Image Orthicon camera tube that formed the basis of most TV signals of that era.

It’s written for the general public, so the scanning raster of a TV image is introduced through the back-and-forth of reading a book, and then translated into how the raster is painted on the screen with the deflection coils and the electron gun. It’s not overly simplified though, for it talks about how the picture is interlaced and shows how a synchronisation pulse is introduced to keep all parts of the system working together.

A particularly fascinating glimpse comes in a brief mention of the solid copper co-axial cable and overland microwave links used to transmit TV signals across country, these concrete towers can still be seen today but they no longer have the colossal horn antennas we can see in the film.

A rather obvious omission in this film is the lack of any mention of colour TV, as while it would be late 1953 before the NTSC standard was formally adopted and early 1954 before the first few colour sets would go on sale. Colour TV would have been very much the Next Big Thing in 1952, but with no transmissions to watch and a bitter standards war still raging between the field-sequential CBS system and RCA’s compatible dot-sequential system that would eventually evolve into the NTSC standard it’s not surprising that colour TV was beyond the consumer audience of the time.

Thus we’re being introduced to the 525-line standard which many think of as NTSC video, but without the NTSC compatible colour system that most of us will be familiar with. The 525-line analogue standard might have disappeared from our living rooms some time ago, but as the last few stations only came off-air last year we’d say it had a pretty good run.

We like analogue TV a lot here at Hackaday, and this certainly isn’t the first time we’ve gone all 525-line. Meanwhile for a really deep dive into the inner workings of TV signal timing, get ready to know your video waveform.

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End Of An Era: NTSC Finally Goes Dark In America

July 14, 2021 by Jenny List 78 Comments

A significant event in the history of technology happened yesterday, and it passed so quietly that we almost missed it. The last few remaining NTSC transmitters in the USA finally came off air, marking the end of over seven decades of continuous 525-line American analogue TV broadcasts. We’ve previously reported on the output of these channels, largely the so-called “FrankenFM” stations left over after the 2009 digital switchover whose sound carrier lay at the bottom of the FM dial as radio stations, and noted their impending demise. We’ve even reported on some of the intricacies of the NTSC system, but we’ve never taken a look at what will replace these last few FrankenFM stations.

If you are an American you may have heard of ATSC 3.0, perhaps by its marketing name of NextGen TV. Just like the DVB-T2 standard found in other parts of the world, it’s an upgrade to digital TV standards to allow for more recent video compression technologies and higher definition broadcasts. It has an interesting backwards compatibility feature absent in previous ATSC versions; there is the option of narrowing the digital bandwidth from 6 MHz to 5.5 MHz, and transmitting an analogue FM subcarrier where the old NTSC sound carrier on the same channel would have sat. Thus the FrankenFM stations have the option of upgrading to ATSC 3.0 and transmitting a digital channel package alongside their existing FM radio station. It’s reported that this switchover is happening, with one example given in the Twitter thread linked above.

The inexorable march of technology has thus given better quality TV alongside the retention of the FrankenFMs. We have to admit to being sorry to see the passing of analogue TV, it was an intricate and fascinating system that provided a testbed for plenty of experimentation back in the day. Perhaps as we see it slip over the horizon it’s worth pondering whether its digital replacement will also become an anachronism in an age of on-demand streaming TV, after all it shouldn’t have escaped most people’s attention that in 2021 the good TV content no longer comes to your screen via an antenna socket. Meanwhile we’ll keep our CRTs running, just in case we ever want to relive a 1980s night in with a VHS tape of Back To The Future.

Header image: Mysid, Public domain.

History Of Closed Captions: The Analog Era

April 14, 2021 by Chris Lott 46 Comments

Closed captioning on television and subtitles on DVD, Blu-ray, and streaming media are taken for granted today. But it wasn’t always so. In fact, it was quite a struggle for captioning to become commonplace. Back in the early 2000s, I unexpectedly found myself involved in a variety of closed captioning projects, both designing hardware and consulting with engineering teams at various consumer electronics manufacturers. I may have been the last engineer working with analog captioning as everyone else moved on to digital.

But before digging in, there is a lot of confusing and imprecise language floating around on this topic. Let’s establish some definitions. I often use the word captioning which encompasses both closed captions and subtitles:

Closed Captions: Transmitted in a non-visible manner as textual data. Usually they can be enabled or disabled by the user. In the NTSC system, it’s often referred to as Line 21, since it was transmitted on video line number 21 in the Vertical Blanking Interval (VBI).

Subtitles: Rendered in a graphical format and overlaid onto the video / film. Usually they cannot be turned off. Also called open or hard captions.

The text contained in captions generally falls into one of three categories. Pure dialogue (nothing more) is often the style of captioning you see in subtitles on a DVD or Blu-ray. Ordinary captioning includes the dialogue, but with the addition of occasional cues for music or a non-visible event (a doorbell ringing, for example). Finally, “Subtitles for the Deaf or Hard-of-hearing” (SDH) is a more verbose style that adds even more descriptive information about the program, including the speaker’s name, off-camera events, etc.

Roughly speaking, closed captions are targeting the deaf and hard of hearing audience. Subtitles are targeting an audience who can hear the program but want to view the dialogue for some reason, like understanding a foreign movie or learning a new language.

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Time’s Almost Up For The FrankenFMs: The Impending Switchoff Of Analog TV

March 13, 2021 by Jenny List 30 Comments

In a time when multi-channel digital TV is the norm it’s a surprise to find that a few low-power analog stations are still clinging on in some American cities. These are sometimes fill-in stations for weak signal areas, or more usually the so-called “FrankenFM” stations who transmit static images or digital patterns and derive income from their sound channel lying at the bottom end of the FM band to form unintended radio stations. Their days are numbered though, because the FCC is requiring that they be turned off by July 13th. There’s a way forward for the broadcasters to upgrade to low-power digital, but as you might expect they’re more interested in retaining the FrankenFM frequency from which they derive income.

The industry is represented by the LPTV coalition, who have requested permission to retain their FM frequency alongside their digital service. This has faced stiff opposition from other broadcasters, who see the very existence of the FrankenFM stations as a flagrant flouting of the rules that shouldn’t be rewarded. The FCC have yet to make a ruling, so there remains a slim chance that they may win a reprieve.

The sad tale of the few lingering analog TV stations in the USA is a last flickering ember of a once-huge industry that has been eclipsed without anyone but a few vintage technology geeks noticing, such has been the success of digital broadcasting. But analog TV is a fascinating and surprisingly intricate system whose passing however faint is worth marking.

Header: Tiia Monto, CC BY-SA 3.0.

The Last Few Analogue TV Stations In North America

January 29, 2021 by Jenny List 40 Comments

Analogue TV is something that most of us consider to have been consigned to the history books about a decade ago depending on where in the world we are, as stations made the transition to much more power and frequency efficient digital multiplexes. However some of them still cling on for North American viewers, and [Antenna Man] took a trip to Upstate New York in search of some of them before their final switch-off date later this year.

What he reveals can be seen in the video below the break, an odd world of a few relatively low-power analogue TV stations still serving tiny audiences, as well as stations that only exist because their sound carrier can be picked up at the bottom of the FM dial. These stations transmit patterns or static photographs, with their income derived from the sound channel’s position as an FM radio station. While his journey is an entertaining glimpse into snowy-picture nostalgia it does also touch on some other aspects of the aftermath of analogue TV boradcasting. The so-called “FrankenFM” stations sound much quieter, we’re guessing because of the lower sound carrier deviation of the CCIR System M TV spec compared to regular FM radio. And we’re told that there are more stations remaining in Canada, so get out there if you still want to see an analogue picture before they’re gone forever. Where this is being written the switch to DVB was completed in 2013, and it’s still a source of regret that we didn’t stay up to see the final closedown.

Does your country still have an analogue TV service? Tell us in the comments.

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Grey Gear: French TV Encryption, 1980s Style

June 25, 2020 by Kristina Panos 38 Comments

Who among us didn’t spend some portion of their youth trying in vain to watch a scrambled premium cable TV channel or two? It’s a wonder we didn’t blow out our cones and rods watching those weird colors and wavy lines dance across the screen like a fever dream.

In the early days of national premium television in America, anyone who’d forked over the cash and erected a six-foot satellite dish in the backyard could tune in channels like HBO, Showtime, and the first 24-hour news network, CNN. Fed up with freeloaders, these channels banded together to encrypt their transmissions and force people to buy expensive de-scrambling boxes. On top of that, subscribers had to pay a monthly pittance to keep the de-scrambler working. Continue reading “Grey Gear: French TV Encryption, 1980s Style” →

Run Your Favorite 8-bit Games On An ESP32

June 9, 2020 by Kerry Scharfglass 20 Comments

Here at Hackaday HQ we’re no strangers to vintage game emulation. New versions of old consoles and arcade cabinets frequently make excellent fodder for clever hacks to cram as much functionality as possible into tiny modern microcontrollers. We’ve covered [rossumur]’s hacks before, but the ESP_8-bit is a milestone in comprehensive capability. This time, he’s topped himself.

There isn’t much the ESP 8-bit won’t do. It can emulate three popular consoles, complete with ROM selection menus (with menu bloops). Don’t worry about building a controller, just connect any old (HID compliant) Bluetooth Classic keyboard or WiiMote you have at hand. Or if that doesn’t do it, a selection of IR devices ranging from joysticks from the Atari Flashback 4 to Apple TV remotes are compatible. Connect analog audio and composite video and the device is ready to go.

The system provides this impressive capability with an absolute minimum of components. Often a schematic is too complex to fit into a short post, but we’ll reproduce this one here to give you a sense for what we’re talking about. Come back when you’ve refreshed your Art of Electronics and have a complete understanding of the hardware at work. We never cease to be amazed at the amount of capability available in modern “hobbyist” components. With such a short BOM this thing can be put together by anyone with an ESP-32-anything.

There’s one more hack worth noting; the clever way [rossumur] gets full color NTSC composite video from a very busy microcontroller. They note that NTSC can be finicky and requires an extremely stable high speed reference clock as a foundation. [rossumur] discovered that the ESP-32 includes a PLL designed for audio work (the “APLL”) which conveniently supports fractional components, allowing it to be trimmed to within an inch of the desired frequency. The full description is included in the GitHub page for the project and includes detailed background of various efforts to get color NTSC video (including the names of a couple hackers you might recognize from these pages).

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