Planet Analog DesignLine Blog
Have you seen any erlangs lately?
Bill Schweber
1/19/2012 12:33 PM EST
I was reading a technical-review article the other day and saw the word "erlangs." All I could think was, "wow, I haven't seen that word in a while!" Back in the day, if you were involved at all with telecommunications, system analysis, or telephony (another fading term, BTW), you knew about erlangs.
"What's an erlang, anyway?" you're asking. To quote from this site, "an Erlang is a unit of telecommunications traffic measurement. Strictly speaking, an Erlang represents the continuous use of one voice path. In practice, it is used to describe the total traffic volume of one hour."
The erlang parameter is based on the idea of a circuit-switched network, with a physical line dedicated to the voice call in progress. By knowing how many erlangs of traffic you had, you could determine how many physical circuit lines you needed in a phone system, whether to serve a business office, or a phone company central office, or for trunk lines between central offices. There are tables and formulas which showed resources needed to provide different thresholds of system availability, for any given number of erlangs of voice traffic.
Things have certainly changed. A dedicated circuit line for a voice call is largely an anachronism, as we now digitize voice, break the resultant data streams into packets, and route them via a packet-switching network. We think of system capacity in terms of bandwidth, data rates, bit error rate, throughput, and other parameters--not erlangs
So the erlang, which served the industry well and was the basis for so much system design and provisioning, has dimmed severely in the lexicon of the telecom engineer. That's how things go in our high-tech world: for a while, you're vital; later on, you're perhaps just a footnote.
Are there any technical terms that you used to see, but no longer do? Are there terms you see which wished you knew what they were about, and why they were used? ◊
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David Ashton
1/19/2012 2:27 PM EST
Takes me back a bit Bill, I also remember Erlangs from my early telephony training.
Another term you don't see much these days in Baud. Mostly used in the teleprinter days when it was equivalent to Bit Rate, but when modems started using techniques like QAM (Quadrature Amplitude modulation) they would transmit a 2400 baud signal (that could use a 3000 Hz bandwidth channel) yet get 9600 bits per second of data (or more) through it. The ratio between the bit rate and the Baud rate was the Symbol rate (ie how many bits you could cram into each Baud. These days it has largely fallen out of use.
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RB3200
2/1/2012 11:33 AM EST
Speak for yourself...
We are still/again using Baud Rate daily in digital telecommunications such as satellite modulation (DVB-S, DVB-S2). Symbol Rate is a modern equivalent which is applied more often. Symbols per second is the same as Baud per second. See wikipedia for definition of symbol rate. See my employer's website for modulator products: sencore.com.
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RWatkins
2/8/2012 10:24 AM EST
Baud is not commonly used, but it is not for lack of an appropriate discussion. Look at your ISP (internet service provider) literature and they are almost universally posting "bits-per-second" specifications. Sounds like baud by any other name to me...
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LiketoBike
1/19/2012 4:19 PM EST
Man, talk about memory lane (I worked at both Nortel and Ericsson)...Ericsson even had a programming language called Erlang!
There are a couple words that have been dropped, but are still around as different words. I am fully aware that even writing these down may confer a certain degree of "old geezer" status :-)
* cps - cycles per second = Hertz (Hz)
* uuF - micromicrofarad = pF
* mho - SI replacement is the Siemen (S)
* Hollerith - a format used in punched cards
* RGB - now we have HDMI :-)
* CGA/EGA/VGA - we just give size & resolution
Right, David, everyone just wants to know the bit rate now :-) I think that baud started to go away when we started doing everything with quadrature modulators...
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zeeglen
1/20/2012 6:58 PM EST
"Are there any technical terms that you used to see, but no longer do?"
Oh yes...
Nepers
Morse (but still active in some circles)
Baudot (ref David's post above)
Condenser, remote cutoff, triode, tetrode, pentode, pentagrid, plate
Grid leak (fetch a bucket)
Film (photographic, not soap or resistor)
Tape (magnetic or paper, not duct)
Card (punched cardboard, not poker or printed circuit assembly)
Floppy (disc, not medical condition)
Galena (AM detector crystal) and Cat Whisker
BFO (beat frequency oscillator)
Q Multiplier
Regenerative
Dang it, Bill, now I am going to be awake all night trying to remember old unused terminology. :-)
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David Ashton
1/21/2012 12:13 AM EST
Floppy disks...right. Back in Zimbabwe, floppy referred to the really floppy 5-1/4 inch ones. When the more rigid 3-1/2 inch ones came along we called them stiffies. It was a good way to specify exactly what you wanted. Fast forward a couple of years and I arrive in Australia. Here (and probably in the states?) "Stiffy" means something totally different. Caused a few laughs when I first got here.....
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LiketoBike
1/23/2012 2:31 PM EST
Oh, you young'uns... :-) Go on back to 8" floppies, for extra floppy :-)
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SteveD_Aus
2/2/2012 5:32 PM EST
Gee Dave, I can just imagine the response here in Oz when you asked someone if they had a stiffy...
Okay. My contribution to this topic shall be logic. Anyone still use HTL, DTL, ECL, or even TTL?
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LiketoBike
1/23/2012 2:30 PM EST
As an amateur radio operator, I still use some of those :-)
As an RF/microwave guy, I still use nepers...
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pomartel
1/21/2012 11:44 AM EST
The programming language Erlang is freely available under the Mozilla Public License
http://www.erlang.org/
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Bert22306
1/19/2012 5:50 PM EST
Although, in industrial and military applications, serial RS-422 and 485, and even the occasional 232, are still used. So I actually do use baud rate still, when dealing with those systems. You need to know the baud rate to set the UART correctly. And the symbol coding too! Like 8N1, remember?
Otherwise, I agree that bit rate is all that matters.
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LiketoBike
1/20/2012 9:14 AM EST
Well, there's one that just slipped out - UART. You only see that as a piece inside a micro these days :-) Remember the 16550? When a UART was a separate IC, and a pretty big one at that...
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David Ashton
1/20/2012 6:23 PM EST
Remember the really old one, and probably the first real UART: the AY3-1015. General purpose thing you could use with just about any uP, and all the settings were selected by pins on the IC, not by programming it....I still have a bunch of them in my IC box and was even thinking about using one for something the other day....
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WA7TUV
1/21/2012 1:53 AM EST
Or the later CMOS equivalent, the HD-6402. I have a box of those around somewhere.
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LiketoBike
1/23/2012 2:29 PM EST
Fond memories there :-)
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jackOfManyTrades
1/20/2012 4:29 AM EST
When I started designing ICs, we used to talk about microns. These days it's all nanometers.
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LiketoBike
1/23/2012 2:29 PM EST
Wait 'til we get to angstroms!!!
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Mark.Rackin
1/24/2012 2:59 PM EST
I started with MILS! I still have my hand-made 1" = 1 Mil aluminum straight-edge/scale that I used for hand-cutting rubylith...
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prabhakar_deosthali
1/20/2012 5:34 AM EST
The most popular printer interface Centronics is now a thing of past as most of the printers run on USB port
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esuurmaa
1/20/2012 7:16 AM EST
LiketoBike, Erlang continues to be an open source general purpose concurrent programming language :-) Latest stable release went out before Christmas, 2011.
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LiketoBike
1/20/2012 9:15 AM EST
I saw that at http://www.erlang.org/
I just don't play in that space (I'm a hardware guy, but did some systems work too :-) )
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FlyByPC
1/20/2012 5:20 PM EST
There are lots of old tech terms that were used with older PC technology: interrupts (still there, but largely hidden by PnP technology), ISA/EISA/VLB busses, EDO and "fast page" RAM, MFM and RLL hard drives (and floppy drives of all types) and many others.
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WKetel
1/20/2012 5:22 PM EST
In the line of programming languages, I was very good with UVOSS, but now it is certainly an unused language. It programmed 6809-based testers for electrical testing of GM products, primarily the U-Vans. Unfortunately progress replaced the very fast testers with much slower windows based systems that were only slightly easier to program and cost five times as much.
Actually I had never heard of the term "erlang" until this article.
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Barton.Meeks
1/20/2012 5:29 PM EST
I remember writing some code in the REXX language on an IBM mainframe to do some erlang calculations, because it was the only thing I had access to that would handle the factorial(512) I had in my formula! The project was canned before I could figure out if what I was doing had any basis in reality.
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ese002
1/20/2012 5:43 PM EST
cps was also "Characters per second". Back when printers printed fixed sized characters. Now a days, printing is entirely graphical so the unit is "pages per minute"
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David Ashton
1/20/2012 6:19 PM EST
Which reminds me of another antique: Dot Matrix Printers! remember those?
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zeeglen
1/20/2012 10:06 PM EST
Yup! Brrrrrrrrrrrt!
And those 132 character line at a time printers? Crash! Feed! Crash! Feed!...
Aren't inkjet and laser printers wonderful?
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IFindNickNamesAnnoying
1/23/2012 10:37 AM EST
I recently saw one in use printing receipts on multiform (carbon paper) paper. Some technology just won't die. Remember those fun days trying to insert loose carbon paper between sheets of paper to use in the typewriter?
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SteveD_Aus
2/2/2012 5:34 PM EST
Typewriter?
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WireMan
1/20/2012 6:01 PM EST
Minicomputer?
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R.C..Ayeras
1/20/2012 8:37 PM EST
Reel-to-reel for running programs, magnetic tape or punch tape
Teletype
DB25, mostly for serial ports (a good indication of how outdated a manual is)
Blue line (copies of drawings, smelly process)
Bit slice (processors that were cascaded to handle more bits in parallel - I only remember back to 4-bit) - and having to cascade logic analyzers to view more than 8 bits.
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DSPer
1/21/2012 3:12 AM EST
Hi,
Yes. And when powering up some of those minicomputers you had to load a short piece of paper tape, called a "boot loader", in the paper tape reader. The data from that tape was loaded into memory which enabled you to load your actual application software from another, much larger, paper tape.
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prabhakar_deosthali
1/21/2012 8:42 AM EST
Where has BASIC ( Beginner's All Purpose Symbolic Instruction Set) gone? In the earlier generation it was like learning alphabets of programming.
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prabhakar_deosthali
1/21/2012 8:43 AM EST
I mean Instruction Code!
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David Ashton
1/21/2012 5:24 PM EST
You can still get it in Basic Stamps, and I think Microchip's PicAxe controllers use it.
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gvgmab
1/21/2012 11:50 AM EST
I sometimes miss the eerie glow of nixie tubes, the only way to display numbers before LEDs were invented.
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AshleyZ
1/24/2012 1:54 PM EST
I'm sort of surprised that 7-segment displays are still quite common. I guess it still does what people want.
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zeeglen
1/24/2012 4:19 PM EST
Years ago there was a flat incandescent version in which each segment was formed from a tungsten wire with the decimal a small "X" shaped tungsten wire. They were not in use for very long, fluorescent and LCD replaced them.
Yes, I miss those nixies. For an interesting look at more old technology visit http://www.electricstuff.co.uk/
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David Ashton
1/24/2012 5:14 PM EST
They were called Numitrons:
http://www.bipom.com/numitron.php
I still have a couple in my spares box - I bought some to repair a customer unit years ago.
I also have some cold cathode 7-seg displays - think nixie technology in a 7-seg display.
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zeeglen
1/24/2012 5:40 PM EST
Yes! The Heathkit digital clocks and SB104 (Solid State Ham Radio Transceiver) used those 7 segment neons. How could I have forgotten?
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David Ashton
1/24/2012 6:12 PM EST
Mine are dual displays with a couple of different decimal points top and bottom. I've fired them up using an HV source and they are quite pretty. I have (I think) 5 x dual units which would do 10 digits, been trying to think of something to use them for......
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zeeglen
1/24/2012 6:33 PM EST
Did not know that Numitrons were still made. Thanks for the link.
The neon 7 seg displays were very nice, thin segments and almost no gaps at the corners.
Since the 7 segment topic has come up, it seems very fortunate that 100's of years ago whoever invented the graphic structure for the numerical digits 0 through 9 did them in such a way that they could be represented by 7 segments plus a decimal point. Fits right in with the binary 8 bit byte. A lucky coincidence?
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David Ashton
1/24/2012 9:08 PM EST
Not sure if they are still made, Glen, and there is no price on that link (unlike most of their other products). I suspect if anyone does have any they'd be old stock.
Our numerals come from Arabic I think? Happy coincidence as you say, more so because 7-seg displays came out before Microprocessor busses were thought of - remember the old 7447 decoders?
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David Ashton
1/24/2012 9:18 PM EST
I see Futurlec has got 7446's (30v open collector version of 7447) for $1.60. Those would drive my neon 7-segs. Hmmmmmm......
(Although neons need around 90v to strike, the driver only needs to absorb the 30V difference between the strike voltage and the extinguish voltage.)
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zeeglen
1/25/2012 12:02 PM EST
Another lucky coincidence is that the same 7 segments can display the Roman alpha characters A through F for hexadecimal.
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pomartel
1/21/2012 11:53 AM EST
BASIC is still around. Microsoft has Visual Basic and Small Basic. There are quite a few chips that run BASIC. The Parallax Basic Stamp sries and Basic Micro's BasicATOM and Nano series come to mind.
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Tcat98370
1/21/2012 11:56 AM EST
Er, Dave and my other virtual friends and COFs. (Certified Old Farts ;) I keep up with a few of my former students... CPS for printers is *still* alive and well, even in the USA.
My friend had to wait to get a new Okidata printer (now USB) because of the flooding in Thailand.
His client uses 'NCR' (carbonless) invoicing. A laser would have to burn through the orgional and copies ;)
So, pass me that cut-sheet feeder LOL!
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David Ashton
1/21/2012 5:44 PM EST
Oki made some fine Dot Matrix printers, as did Epson. Another good one was the TI (Texas) 810. Airlines used to love them as ticket printers (remember airline tickets??) because they could produce 8 or more legible copies.
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danner
1/21/2012 4:24 PM EST
Old-timers, indeed - how about an Eccles-Jordan, or Napiers?
Alec
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David Ashton
1/21/2012 5:41 PM EST
How about this. Log(arithm) tables and slide rules. I got taught how to use log tables early in high school, but by the time I finished calculators were widespread. A slide rule was more or less a mechanical version of a log table. Logs live on in deciBels (dB) which are still in widespread use.
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zeeglen
1/21/2012 7:51 PM EST
Good one! David (and everyone else too) do you still remember how to use your slide rule?
I still have mine, but would need to re-learn it for anything other than basic multiplication and division. And there is that danged decimal point, where does it go now...
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David Ashton
1/22/2012 2:18 AM EST
I never actually owned one but I did learn the basics. If you were a whiz with them you could do some awesome stuff. And your mental arithmetic had to be spot on for the decimal points....
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IFindNickNamesAnnoying
1/23/2012 10:44 AM EST
They're now collectable items. If you want a sliderule in good shape you have to spend a fair bit of money to get it. A friend of mine is hooked into that side of things. My old Pickett is still in the cabinet.
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LiketoBike
1/23/2012 2:33 PM EST
I carry a 6" Pickett in my briefcase in case the calculator batteries die :-) It's also good for war stories! And for certain kinds of calculations, it's actually pretty fast...
I confess, though, that I picked it up out of curiosity and wanting to experience the roots of our profession. By the time I got to college, we DID all have scientific calculators...
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Mark.Rackin
1/24/2012 3:06 PM EST
My old yellow Pickett 1010ES hangs on the wall of my home office, with a sign reading "For Emergency Use in case of Computer Failure"!
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RWatkins
2/8/2012 10:39 AM EST
Amen! One of my favorite old time jokes was the one about Noah and adders... Tell that one today and all you get are blank stares.
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Bohdan.Bodnar
1/23/2012 11:46 AM EST
I use erlang calculations for sizing IP links and radio channels. An erlang is nothing more than the mean number of simultaneous (traffic carrying) connections. If you've only one connection on a link, it corresponds to the link's utilization.
There's a nice numerically-stable approach that doesn't require factorial calculations; a good reference is ITU's teletraffic theory manual (free, on-line at ITU.int).
I have a nice engineering slide (K&E, if I remember) that's in mint condition. Some 15 years ago I threatened to sit next to my boss's office with it, pretend I'm doing calculations, and loudly mumble about not having a fast computer for doing embedded system simulation work. I had the computer within a week :-)
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sharps_eng
1/23/2012 3:39 PM EST
body-end-spot
Daisy wheel
wirewrap
eprom eraser; I also had a Dataman UV strobe 'torch' that worked fine
device programmer: PALs, GALs (aren't they still current some places?)
shellac - mmmmm
lacing cord
(everyone's mentioned the computing stuff - except maybe Kansas City coding?)
Of course I knew what a google was before I knew most of this stuff - and a googleplex. Haven't needed any bigger numbers since then, though.
Slow glass? Hmm, looking forward to that.
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divide_by_zero
1/25/2012 11:09 AM EST
Erlangs. Sounds kinda like furlongs. Erlangs per fortnight?
I worked with graybeards from the remnants of Chicago's TV industry as the US monochrome video monitor industry was dying 15-20 years ago. I did stump them when I mentioned the Ruhmkorff coil. Such a nice, quaint term.
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Compotek_LB
1/26/2012 6:04 AM EST
What about "modula2" and "Pascal"?
And does anyone remember VESA local bus (VLB)? - Amazing that this system started just 20 years ago for the 80486 systems and vanished again with the first Pentium boards...
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Jay Sinnett
1/30/2012 2:42 PM EST
Do you remember when the cover article on Electronics Design was "It's a 5V world"? There were now memory chips, logic chips, and microprocessors that all worked from a single 5V supply; no +/- 12 V needed! Wow.
And how about 7400, 74S00, 74LS00, 74C00, 74HC00...?
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RWatkins
2/8/2012 10:43 AM EST
Goodbye and good riddance from me, especially for 74L... and their occasionally non-standard pinouts with standard part numbers. Their children live on today with 74HC (yes we used a new one of those 74HC parts in a prototype less than a year ago) 74LVC, etc.
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David.Tallon
1/31/2012 10:23 AM EST
Here's am old term for you. Anyone know what an aquadag is?
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zeeglen
1/31/2012 12:40 PM EST
Yup. The conductive coating on the outside of a CRT, forms a high voltage filter capacitor with the coating (usually aluminum for TV use) on the inside of the CRT. Generally contacted by a long spring stretched across the aquadag coating and hooked to chassis ground at the ends.
A sneaky side effect of those ol;d CRTs was after removal and discharge of the high voltage, a few thousand volts would build up again. The rule was always discharge the anode well connection to the aquadag before handling a CRT, even when in the box.
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David.Tallon
1/31/2012 3:00 PM EST
DING! You are absolutely correct.
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RWatkins
2/8/2012 10:46 AM EST
One more rule that is embedded in my memory was that you had to discharge the CRT daily when working on a TV or suffer potentially severe shocks. An old Curtis-Mathis 25KV CRT gave me an unforgettable lesson there.
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BicycleBill
2/1/2012 3:53 PM EST
What about Lissajous patterns?--always fascinating!
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zeeglen
2/1/2012 4:23 PM EST
Especially when projected through a large lens onto a wall from an old TV with an added deflection coil, back-to-back electrolytics (I think about 100 uF) to phase shift the vertical winding signal, 20 watt amplifier with low pass filter to respond to bass notes only, and heavy rock music.
My buddies would stare for hours, mesmerized by the flickering patterns pulsing to the music. You know, like, "Wowwww, maaan!"
I wish I could have found a junked colour TV, that would have been even better.
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SteveD_Aus
2/2/2012 5:42 PM EST
One lives on and is quite prominent in the consciousness of Australians, even if they don't realise its meaning:
http://en.wikipedia.org/wiki/Australian_Broadcasting_Corporation#The_Lissajous_curve_logo
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luchenbe
2/2/2012 8:53 AM EST
Erlangs are in a way still here as it was a way of calculating the blocking risk for a certain resource with a certain rated capacity. You still have something similar in a packet switched network where several concurrent users or applications compete for the available bandwidth. QOS (quality of service) mechanisms are there to favour timing critical applications, but there is still a certain blocking risk that can be estimated via techniques very similar to the Erlangs calculation methodology.
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