The pulse-dial telephone and its associated mechanical exchange represents the pinnacle of late-19th and early-20th century electromechanical technology, but its vestiges have disappeared from view with astonishing rapidity. [Matthew Harrold] is a telecoms enthusiast who’s been kind enough to share with us the teardown and refurbishment of that most signature of pulse-dial components, a telephone dial. In this case it’s on a rather unusual instrument, a British GPO outdoor phone that would have been seen in all kinds of industrial and safety installations back in the day and can probably still be found in the wild today if you know where to look.
The teardown soon identifies a dial that runs very slowly and is sorely in need of a clean. There follows a detailed part-by-part dismantling of the dial mechanism, followed by a careful clean, polish, and reassembly. He notes that a previous owner had used grease to lubricate it, probably the reason for its slow operation.
The result is a smoothly running dial and a refurbished phone that would probably last another half-century or more before needing more maintenance. It’s enough to make others who’ve experimented with pulse dial phones very envious.
It may seem like an odd concept to younger readers, but there was once a time when people rented their phones rather than buying them outright. Accordingly, these phones were built like tanks, and seeing one of these sturdy classics of midcentury modern design can be a trip down memory lane for some of us. So retrofitting a retro phone with a Raspberry Pi and Google’s AIY seems like a natural project to tackle for nostalgia’s sake.
The phone that [Alasdair Allan] decided to hack was the iconic British desk telephone, the GPO-746, or at least a modern interpretation of the default rental phone from the late 60s through the 70s. But the phone’s looks were more important than its guts, which were stripped away to make room for the Raspberry Pi and Google AIY hat. [Alasdair] originally thought he’d interface the Pi to the rotary dial through DIOs, until he discovered the odd optical interface of the dialer — a mask rotates over a ring of photoresistors, one for each digit, exposing only one to light from an LED illuminated by a microswitch on the finger stop. The digital interface brings up the Google voice assistant, along with some realistic retro phone line sounds. It’s a work in progress, but you can see where [Alasdair] is in the video below.
If stuffing a Google Pi into a retro appliance sounds familiar, it might be this vintage intercom rebuild you have in mind, which [Alasdair] cites as inspiration for his build.
One of the most famous lectures in the history of technology was delivered by [Douglas Engelbart] in December 1968, at a San Francisco conference. In it he described for the first time most of what we take for granted in our desktop computers and networking today, several years before even the first microprocessor made it to market. It is revered not only because it was the first airing of these ideas, but because it was the event that inspired and influenced many of those who developed them and brought them to market. You may have heard of it by its poplar name: the Mother of All Demos.
This was an exciting time to be a technologist, as it must have been obvious that we lay on the brink of an age of ubiquitous computing. [Engelbart] was by no means alone in looking to the future and trying to imagine the impact that the new developments would have in the decades to come. On the other side of the Atlantic, at the British Post Office Telephone research centre at Dollis Hill, London, his British counterparts were no less active with their crystal ball gazing. In 1969 they produced our film for today, entitled complete with misplaced apostrophe “Telecommunications Services For The 1990’s” , and for our 2017 viewpoint it provides a quaint but fascinating glimpse of what almost might have been.
You can have any phone you want, as long as it’s state-owned! A GPO 746 telephone from the early 1970s.
Until the 1980s, the vast majority of British telephone services were a tightly regulated state monopoly run as part of the Post Office. There were only a few models of telephone available in the GPO catalogue, all of which were fixed installations with none of the phone sockets we take for granted today. Accessories such as autodiallers or answering machines were eye-wateringly expensive luxuries you’d only have found in offices, and since the fax machine was unheard of the height of data transfer technology was the telex. Thus in what later generations would call consumer information technology there really was only one player, so when they made pronouncements on the future they were a good indication of what you were likely to see in your home.
The film starts with a couple having a conversation, she in her bedroom and he in a phone box. Forgotten little touches such as a queue for a phone box or the then-cutting-edge-design Trimphone she’s using evoke the era, and the conversation leaves us hanging with the promise that their conversation would be better with video. After the intro sequence we dive straight into how the GPO thought their future network would look, a co-axial backbone with local circuits as a ring.
The real future-gazing starts with an office phone call to an Australian, at which we’re introduced to their concept of video calling with a colour CRT in a plastic unit that could almost be lifted from the set of The Jetsons. The presenter then goes on to describe a mass information service which we might recognise as something like our WWW, before showing us the terminal in more detail. Alongside the screen is a mock-up of a desktop console with keypad, cassette-based answerphone recorder, and a subscriber identity card slot for billing purposes. Period touches are a brief burst of the old harsh dial tone of a Strowger exchange, and mention of a New Penny, the newly-Decimalised currency. We’re then shown the system transmitting a fax image, of which a hard copy is taken by exposing a photographic plate to the screen.
Perhaps the most interesting sequence shows their idea of how an online information system would look. Bank statements and mortgage information are retrieved, though all with the use of a numeric keypad rather than [Englebart]’s mouse. Finally we see the system being used in a home office, a situation shown as farcical because the worker is continually harassed by his children.
Scorecard
This was the cutting edge in 1980, at least for people who hadn’t seen France’s Minitel. Fair use, via Wikimedia Commons.
So nearly five decades later, what did they get right and how much did they miss? The area you might expect them to be most accurate is oddly the one in which they failed most. The BT telecommunications backbone is now fibre-optic, and for the vast majority of us the last mile or two is still the copper pair it would have been a hundred years ago. In terms of the services though we have all of the ones they show us even if not in the form they envisaged. Fax and answering machines were everyday items by the 1980s, and though it didn’t gain much traction at the time we had video calling as a feature of most offices by the 1990s. We might however have expected them to anticipate a fax machine with a printer, after all it was hardly new technology. Meanwhile the online service they show us is visibly an ancestor of Prestel, which they launched for the late 1970s and which failed to gain significant traction due to its expense.
Another area they miss is wireless. We briefly see a pager, but even though they had a VHF radio telephone service and the ancestors of our modern cellular services were on the drawing board on the other side of the Atlantic at the time, they completely miss a future involving mobile phones.
The full film is below the break. It’s a charming period production, and the wooden quality of the action shows us that while the GPO engineers might have been telephone experts, they certainly weren’t actors.
