Imagine having to program your computer by rewiring it. For a brief period of time around the mid-1940s, the first general-purpose electronic computers worked that way. Computers like ENIAC initially had no internal storage for code. Programming it involved manipulating thousands of switches and cables. The positions of those switches and cables were the program.
Kathleen Booth began working on computers just as the idea of storing the program internally was starting to permeate through the small set of people building computers. As a result, she was one of the first programmers to work on software and is credited with inventing assembly language. But she also got her hands dirty with the hardware, having built a large portion of the computers which she programmed. She also did some early work with natural language processing and neural networks. And this was all before 1962, making her truly a pioneer. This then is her tale.
Continue reading “Kathleen Booth: Assembling Early Computers While Inventing Assembly”
There is one thing that unites almost every computer and logic circuit commonly used in the hardware hacking and experimentation arena. No matter what its age, speed, or internal configuration, electronics speak to the world through logic level I/O. A single conductor which is switched between voltage levels to denote a logic 1 or logic zero. This is an interface standard that has survived the decades from the earliest integrated circuit logic output of the 1960s to the latest microcontroller GPIO in 2018.
The effect of this tried and true arrangement is that we can take a 7400 series I/O port on an 8-bit microcomputer from the 1970s and know with absolute confidence that it will interface without too much drama to a modern single-board computer GPIO. When you think about it, this is rather amazing.
It’s tempting to think then that all logic level outputs are the same, right? And of course they are from a certain viewpoint. Sure, you may need to account for level shifting between for example 5V and 3.3V families but otherwise just plug, and go, right? Of course, the real answer isn’t quite that simple. There are subtle electrical differences between the properties of I/O lines of different logic and microcontroller families. In most cases these will never be a problem at all, but can rear their heads as edge cases which the would-be experimenter needs to know something about.
Continue reading “Behind The Pin: Logic Level Outputs”
Rockets with nuclear bombs for propulsion sounds like a Wile E. Coyote cartoon, but it has been seriously considered as an option for the space program. Chemical rockets combust a fuel with an oxidizer within themselves and exhaust the result out the back, causing the rocket to move in the opposite direction. What if instead, you used the higher energy density of nuclear fission by detonating nuclear bombs?
Detonating the bombs within a combustion chamber would destroy the vehicle so instead you’d do so from outside and behind. Each bomb would include a little propellant which would be thrown as plasma against the back of the vehicle, giving it a brief, but powerful push.
That’s just what a group of top physicists and engineers at General Atomic worked on between 1958 and 1965 under the name, Project Orion. They came close to doing nuclear testing a few times and did have success with smaller tests, exploding a series of chemical bombs which pushed a 270-pound craft up 185 feet as you’ll see below.
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Recently I spent an enjoyable weekend in Canterbury, staying in my friend’s flat with a superb view across the rooftops to the city’s mediaeval cathedral. Bleary-eyed and in search of a coffee on the Sunday morning, my attention was immediately drawn to one of her abode’s original built-in features. There on the wall in the corner of the room was a mysterious switch.
Housed on a standard-sized British electrical fascia was a 12-position rotary switch, marked with letters A through L. An unexpected thing to see in the 21st century and one probably unfamiliar to most people under about 40, I’d found something I’d not seen since my university days in the early 1990s: a Rediffusion selector switch.
If you have cable TV, there is probably a co-axial cable coming into your home. It is likely to carry a VHF signal, either a series of traditional analogue channels or a set of digital multiplexes. “Cable ready” analogue TVs had wideband VHF tuners to allow the channels to be viewed, and on encrypted systems there would have been a set-top box with its own analogue tuner and decoder circuitry.
Your digital cable TV set-top box will do a similar thing, giving you the channels you have subscribed to as it decodes the multiplex. At the dawn of television transmission though, none of this would have been possible. Co-axial cable was expensive and not particularly high quality, and transistorised wideband VHF tuners were still a very long way away. Engineers designing the earliest cable TV systems were left with the technology of the day derived from that of the telephone networks, and in Britain at least that manifested itself in the Rediffusion system whose relics I’d found.
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Given its appearance in one form or another in all but the cheapest audio gear produced in the last 70 years or so, you’d be forgiven for thinking that the ubiquitous VU meter is just one of those electronic add-ons that’s more a result of marketing than engineering. After all, the seemingly arbitrary scale and the vague “volume units” label makes it seem like something a manufacturer would slap on a device just to make it look good. And while that no doubt happens, it turns out that the concept of a VU meter and its execution has some serious engineering behind that belies the really simple question it seeks to answer: How loud is this audio signal?
Continue reading “The VU Meter and How It Got That Way”
If you look up Bing Crosby in Wikipedia, the first thing you’ll notice is his real name was Harry. The second thing you’ll read, though, is that he is considered the first “multimedia star.” In 1948, half of the recorded music played on the air was by Bing Crosby. He also was a major motion picture star and a top-selling recording artist. However, while you might remember Bing for his songs like White Christmas, or for his orange juice commercials, or for accusations of poor treatment from his children, you probably don’t associate him with the use of magnetic tape.
In a way, Bing might have been akin to the Steve Jobs of the day. He didn’t power the technology for tape recording. But he did see the value of it, invested in it, and brought it to the market. Turns out Bing was quite the businessman. Want to know why he did all those Minute Maid commercials? He was a large shareholder in the company and was the west coast distributor for their products. He also owned part of the Pittsburgh Pirate baseball team and other businesses.
So how did Bing become instrumental in introducing magnetic tape recording? Because he was tired of doing live shows. You see, in 1936, Crosby became the host of a radio variety show, The Kraft Music Hall. This very popular program was live. That means you have to show up on time. If you go off on a tangent, you’ll run out of time. And if you make a mistake, there is no editing. Oh and one other thing. You have to do a nationwide live show twice: once for the east coast and another for the west. This was cutting into Bing’s “family time” which, as far as we can ascertain was a code phrase for golf.
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It’s high summer here in North America, and for a lot of us, this one has been a scorcher. Media reports have been filled with coverage of heat wave after heat wave, with temperature records falling like dominoes.
But as they say, it’s not the heat, it’s the humidity, and that was painfully true in the first week of July as a slug of tropical air settled into the northeast United States. With dewpoints well into the 70s (25°C plus) and air temperatures pushing the century-mark (38°C), people suffered and systems from transportation to the electrical grid strained under the load. But as punishing as such soupy conditions are for people, there are other effects that are less well known but of critical importance to financial markets, where increased humidity can lead to billion-dollar losses for markets. Welcome to the weird world of high-frequency trading.