The basic principle relies on an analog circuit that detects the AC ringing signal from the phone network, and then switches in an impedance to make the phone company think the phone has been picked up. The circuit is able to operate solely on the voltage from the phone line itself, thanks to the use of the LM2936 – a regulator with an ultra-low quiescent current. It’s important if you’re going to place a load on the phone line that it be as miniscule as possible, otherwise you’ll have phone company technicians snooping around your house in short order wondering what’s going on.
The aforementioned circuitry is just to block the phone line. To enable the system to only work at night, more sophistication was needed. An Arduino Mega was used to program an advanced RTC with two alarm outputs, and then disconnected. The RTC is then connected to a flip-flop which connects the blocking circuit only during the requisite “quiet” hours programmed by the Arduino. The RTC / flip-flop combination is an elegant way of allowing the circuit to remain solely powered by the phone line in use, as they use far less power when properly configured than a full-blown microcontroller.
It’s a cool project, with perhaps the only pitfall being that telecommunications companies aren’t always cool with hackers attaching their latest homebrewed creations to the network. Your mileage may vary. For more old-school telephony goodness, check out this home PBX rig.
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.
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.
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.
It is hard to remember, but there was a time when you couldn’t hook much to a telephone line except a telephone. Although landlines are slowly falling out of favor, you can still get corded and wireless phones, answering machines, and even dial up modems. Alarm systems sometimes connect to the phone system along with medical monitoring devices and a host of other accessories.
All of that’s possible because of a Texan named Tom Carter. Tom Carter was the David that stood up to one of the biggest Goliath’s of his day: the phone company. The phone company had a legal monopoly on providing phone service. The reasoning was that it didn’t make sense to have multiple competing companies trying to run wires to every house and business in the country. Makes sense, right?
We take recorded telephone messages for granted in these days of smartphones and VOIP. Our voicemail lives on an anonymous server in a data centre in the cloud somewhere, in a flash memory chip on our DECT base station, or if we’re of a retro persuasion, on a micro-cassette. Wherever we go, we now know our calls will not go unanswered.
Today’s subject takes us back to a time when automatically recording a phone call was the last word in high technology, with a British Pathé newsreel piece from 1959 entitled “Modern Telephone”. Its subject is the Ansafone J10, one of the first telephone answering machines available on the British market. After featuring a fantastic home-made Meccano answering machine with turntable recording created by a doctor, it takes us to the Ansafone factory where the twin tape mechanisms of the commercial model are assembled and tested. Finally we get to see it in use on the desk of a bona fide Captain of Industry, probably about the only sort of person who could afford an Ansafone in 1959.
The game of Chinese Whispers or Telephone involves telling one person a sentence, having that person tell another person the same sentence, and continuing on until purple monkey dishwasher. For this year’s Arduino Day, [Mastro] was hanging out at Crunchlab with a bunch of Arduinos. What do you do with a bunch of Arduinos? Telephone with software serial.
The setup for this game is extremely simple – have one Arduino act as the master, listening for bits on the (hardware) serial port. This Arduino then sends those bits down a chain of Arduinos over the software serial port until it finally loops around to the master. The result is displayed in a terminal.
With only about a dozen Arduinos in this game of Telephone, [Mastro] did get a few transmission errors. That’s slightly surprising, as the code is only running at 1200 bps, but the point of this game isn’t to be completely accurate.
Imagine this. A phone on a nearby desk starts ringing. No one is around to pick it up, so you decide that you will be a good Samaritan and answer the phone. You are greeted by a slightly creepy robotic female voice asking you to complete a simple survey. Having nothing else to do, you go ahead and run through the telephone survey. As you start answering the questions, things start to get a bit… weird. The robot voice doesn’t like your answers. She actually disagrees with you, and she does NOT like being interrupted. Now she’s getting sassy with you! What is going on here?
Most likely you are the latest victim of Insert Customer Feedback Here, [Charles’] art installation. You see, that is no ordinary telephone. [Charles] actually removed the guts of an old telephone and replaced them with an Arduino. The Arduino periodically rings the phone, waiting for someone to answer. Once the phone is off the hook, the Arduino uses a Wave shield to start playing back the scripted audio files. All of the text-to-speech files and the various hold music files are played back with the wave shield. The Arduino is also hooked up to the 1, 2, 3, and # keys of the telephone keypad in order to read back the user’s responses.
From here on out the program acts as a sort of “choose your own adventure” game. The program takes different paths and responds in different ways depending on how the user answers the questions. Generally speaking, it will get more “irritated” towards the user if it doesn’t “like” your answers, otherwise it will get less irritated. The hold music will even change to become more or less aggressive.
It looks like a consumer good, but this PBX server blade was built by [Benoit Frigon] over the last couple of years. It brings multiple telephone extensions to his home service.
The device runs Asterisk open source PBX software. Because it will be on all the time he wanted something that doesn’t draw a lot of power. The 500 Mhz system seen on the left has just a half a gig of ram. It’s enough to do the job and at 10 Watts it’s not going to break the bank when it comes to paying the electric bills. The board in the middle is used to interface the analog handsets with the land line. From the look of it he’s got it rigged for two extensions.
That’s all somewhat par for the course with PBX rigs, but the enclosure is where he really shines. [Benoit] used 22 gauge aluminum sheet to fabricate the enclosure which is designed to blend in with the rest of his home’s rack mount hardware. To provide control at the rack he added his own LCD and touch-sensitive button interface to the front of the case based on a PIC 18F2520. The system can also be accessed via the web thanks to a custom interface he coded.