This gem from the AT&T Archive does a good job of explaining the first-generation cellular technology that AT&T called Advanced Mobile Phone Service (AMPS). The hexagon-cellular network design was first conceived at Bell Labs in 1947. After a couple of decades spent pestering the FCC, AT&T was awarded the 850MHz band in the late 1970s. It was this decision coupled with the decades worth of Bell System technical improvements that gave cellular technology the bandwidth and power to really come into its own.
AT&T’s primary goals for the AMPS network were threefold: to provide more service to more people, to improve service quality, and to lower the cost to subscribers. Early mobile network design gave us the Mobile Service Area, or MSA. Each high-elevation transmitter could serve a 20-mile radius of subscribers, a range which constituted one MSA. In the mid-1940s, only 21 channels could be used in the 35MHz and 150MHz band allocations. The 450MHz band was introduced in 1952, provided another 12 channels.
The FCC’s allocation opened a whopping 666 channels in the neighborhood of 850MHz. Bell Labs’ hexagonal innovation sub-divided the MSAs into cells, each with a radius of up to ten miles.
The film explains quite well that in this arrangement, each cell set of seven can utilize all 666 channels. Cells adjacent to each other in the set must use different channels, but any cell at least 100 miles away can use the same channels. Furthermore, cells can be subdivided or split. Duplicate frequencies are dealt with through the FM capture effect in which the weaker signal is suppressed.
Those Bell System technical improvements facilitated the electronic switching that takes place between the Mobile Telephone Switching Office (MTSO) and the POTS landline network. They also realized the automatic control features required of the AMPS project, such as vehicle location and automatic channel assignment. The film concludes its lecture with step-by-step explanations of inbound and outbound call setup where a mobile device is concerned.
Continue reading “Retrotechtacular: Ma Bell’s Advanced Mobile Phone Service (AMPS)”
This is the under-the-hood view of the keyboard for the Voder (Voice Operating Demonstrator), the first electronic device capable of generating continuous human speech. It accomplishes this feat through a series of keys that generate the syllables, plosives, and affricatives normally produced by the human larynx and shaped by the throat and tongue. This week’s film is a picture montage paired with the audio from the demonstration of the Voder at the 1939 World’s Fair.
The Voder was created by one [Homer Dudley] at Bell Laboratories. He did so in conjunction with the Vocoder, which analyzes human-generated speech for encrypted transfer and re-synthesizes it on the other end. [Dudley] spent over 40 years researching speech at Bell Laboratories. His development of both the Voder and the Vocoder were instrumental in the SIGSALY project which aimed to deliver encrypted voice communication to the theatres of WWII.
Continue reading “Retrotechtacular: The Voder from Bell Labs”
At the Vintage Computer Festival last weekend, there was a wonderful representation of small 8 and 16-bit home computers from the 80s, an awful lot of PDP and VAX-based minicomputers, and even some very big iron in the form of a UNIVAC and a Cray. You might think this is a good representation of computing history, but there was actually a huge gap in the historical reality. Namely, workstations and minicomputers that weren’t made by DEC.
[Ian Primus] was one of the very few people to recognize this shortcoming and brought his PRIME minicomputer. This was a huge, “two half racks, side by side” computer running PRIMOS, an operating system written in FORTRAN. Of course this made it extremely popular with engineering teams, but that doesn’t mean [Ian] can’t have fun with it. He had two terminals set up, one running Dungeon (i.e. Zork pre-Infocom) and a text-based lunar lander game.
Because the VCF East is held in New Jersey, it’s probably no surprise a few vintage AT&T Unix boxes showed up. [Anthony Stramaglia] brought in a few very cool vintage Unix workstations, dating from the early to mid 80s. In the video, he shows off two AT&T boxes. The first is a UNIX PC, containing a 68010 clocked at a blistering 10 MHz. Next up is the UNIX PC’s bigger brother, the 3B2 400. This is the workstation found on just about every desk at Bell Labs in the 80s, meaning this is the same computer [Ken Thompson] and [Dennis Ritchie] used for their work on UNIX.
Continue reading “VCF East: PR1ME And AT&T Unix Boxes”
Few births are easy. Even fewer result in a Nobel Prize, and hardly any at all are the work of three men. This 1965 film from the AT&T archives is a retrospection on the birth of the transistor nine years after its creators, [Walter Brattain], [John Bardeen], and [William Shockley] received a Nobel Prize in Physics for their discovery and implementation of the transistor effect.
The transistor is the result of the study of semiconductors such as germanium. Prior to the research that led directly to the transistor, it was known that the conductivity of semiconductors increases when their temperature is raised. The converse is true for metals such as tungsten. Semiconductor conductivity also increases when they are exposed to light. Another key to their discovery is that when a metal such as copper is in contact with a semiconductor, conductivity is less in one direction than the other. This particular property was exploited in early radio technology as seen in crystal radios, for copper oxide rectifiers used in telephony, and for microwave radar in WWII.
After WWII, AT&T’s Bell Labs put a lot of time and research into the study of semiconductors, as their properties weren’t fully understood. Researchers focused on the simplest semiconductors, silicon and germanium, and did so in two areas: bulk properties and surface properties. During this time, [Shockley] proposed the field effect, supposing that the electrons near the surface of a semiconductor could be controlled under the influence of an external electric field.
Continue reading “Retrotechtacular: The Genesis of the Transistor”
Modern operating systems may seem baroque in their complexity, but nearly every one of them – except for Windows, natch – are based on the idea of simplicity and modularity. This is the lesson that UNIX taught us, explained perfectly in a little film from Bell Labs in 1982 starring giants of computation, [Dennis Ritchie], [Ken Thompson], [Brian Kernighan], and others.
At the time this film was made, UNIX had been around for about 10 years. In that time, it had moved far from an OS cloistered in giant mainframes attached to teletypes to slightly smaller minicomputers wired up to video terminals. Yes, smallish computers like the Apple II and the VIC-20 were around by this time, but they were toys compared to the hulking racks inside Bell Labs.
The film explains the core concept of UNIX by demonstrating modularity with a great example by [Brian Kernighan]. He took a short passage from a paper he wrote and found spelling errors by piping his paper though different commands from the shell. First the words in the paper were separated line by line, made lowercase, and sorted alphabetically. All the unique words were extracted from this list, and compared to a dictionary. A spell checker in one line of code, brought to you by the power of UNIX.
This installment of Retrotechtacular looks at a video lecture that is much more substantive than the usual fare. [Dr. J.N. Shive] was a researcher at Bell Labs at a time when just about every technological breakthrough was coming from that singular collection of minds.
This video, called Similarities of Wave Behavior, was made to help bring students up to speed on the principles of waves. To aid in the experience he invented the apparatus seen in front of him. It’s called a Shive Wave Machine (in the prelude to the video they call it the Shive Wave Generator). Having not taken any physics classes at University we hadn’t seen one of these devices before. It uses a series of horizontal rods connected to each other with torsion wire. When you upset the balance of one of the rods the wire conducts that energy to its neighbors as an energy wave. This turns out to be a perfect representation of wave action whether it be mechanical, electrical, or acoustic. The 28-minute video after the break makes extensive use of the device, and explains concepts in a way that is easy to understand for just about anyone.
Continue reading “Retrotechtacular: Similarities of Wave Behavior”
Don’t get your dirty fingers on the glass
[Poke] sent in a video of him using Android devices with a wiimote and PS3 controller. The build uses the Joystick2Touch and the USB Joystick Center app. Root is required, but this will be very useful when tv-sized Android devices start showing up.
Wonderful restoration work
[John] sent in an Instructable on restoring an ancient typewriter. It’s almost beautiful seeing all those delicate metal parts so finely cleaned and reassembled.
Proof of the Big Bang is in one of these articles
[Paleotechnoligist] has been reading the technical journals from Bell Labs. These people were the Google of the 20th century and did some amazing stuff. Here’s the math for getting to the moon and a thing about “cellular telephony.”
Oooohhh extruded aluminum
[Richard Sum] sent us a pic of his new 3D printer kit he’ll be offering soon. Very professional looking.
Flying like a three dollar bill
[Yannick] and [SaakNeMah] sent in this video of a guy strapping on bird wings, running down a field, and then flying for about 100 meters. The project is Human Birdwings and it’s gotten an amazing amount of press coverage. We’re calling fake on this for three reasons: the wings didn’t produce lift, the camera angles are all wrong (only applicable if there was a single flight), and this guy would be a gazillionaire if his wings actually worked. Argue amongst yourself in the comments; we’d love to be proven wrong.