Pragmatic 65: Everything is Analogue

23 October, 2015

CURRENT

We tackle the subtle differences between analogue and digital data transmission and why frequency changes everything.

Transcript available
Welcome to pragmatic is a discussion show concertina practical application of technology by exploring the real trade-offs we look at how great ideas are transformed into products and services that can change our lives nothing is as simple as it seems pragmatic is brought to you by many tricks makers of helpful apps for the Mac visit many tricks or one word.com/engineered more information about their amazingly useful apps will talk more about them during the show pragmatic as part of the engineered network of other great shows that engineered.network today I'm your host John Geagea and I joined my co-host Carmen Parisi Hayden, Grigor John W.well was so yeah so on a dive straight into this episode arm and I like to call this everything is analog because it sounded as he how you would like the sound of one of the things that I found fascinating about digital is the the idea that things will have a discrete statements either on or it off but the truth is that that's just not reality it's it's, like how mathematics is is an approximation arousing masses is always not real you know there's no such thing as one of something that is itching is to have something it's always an approximation and I want to go into that too much but I'm a big beacon was trivia rating will now get 30 seconds and I sorry about that anyway but anyway the point is I won't dig into the differences between analog and digital white is the way it is and why digitals really analog so this can organise and be riders know it is but that's okay I don't care so I did talk about some of the things undercover guns episode but I really did skim over them last time it was in episode 12 about six minutes eight seconds in and again at eight minutes 30 seconds in for about a minute and 1/2 each roughly but we are dive a lot deeper than that into the theory behind why things evolve the way they are and why we are where we are and why would make such a silly statement like everything is analog so arm would you like to describe to the listeners are what an analog signal is short I analog signal are in the time domain is continuously varying sold now if you're trying to measure the signal at any point in time you can shrink down time to heal some infant has not scaled it in the physicist said doesn't exist and there should still be of value there on United yellow can exist in any amplitude so you measure the voltage can get under microvolts nanovolts pickle vaults if you want your crazy frontal vaults are there is not just one or two different levels can exist at excellent very good are digital because then it is suggested is it's either one state all the other is either onerous offers one or zero bugs the problem is in the real world's if we just won't talk about voltage levels for example are which is one method of carrying digital information digital logic is in that case about the voltage level but how do we determine what is a logic one in what's a logic zero so digitally we carry data you these days Silicon bio rad transistors and real-world examples of those historically are things like CMOS are excellent TTL so you know you've got to our emitter couple logic and TTL as a transistor transistor logic before about you Dale transistor and resistor transistor you flavours so soup absolutely and you could go back to valves if you really really want to but in okra valve diodes and so on but you honest I want to be selfish and go TTL because I play with TTL predominately when I was younger so you know what hey, A TTL just briefly so logic zero in the case TTL for example is when an analog voltage is between zero vaults and 0.8 vaults the region from 0.8 vaults to 2 vaults is technically undefined and then from two vaults to VCC our BCC typically being 4.752 5.25 that's a logic one your you often see VCC written down yours as the others IVD of the assessment if you want what they are is that voltage from our collector to collector are or collector collector voltage if you think about that way so what that's all about is the Trent bipolar junction transistors will be JT's as they sometimes called the have a basic collector and emitter and one of the TTL connection structures are involves our collector's multiple collectors tied together to a source voltage and that gives rise to the expression VCC but the truth is that there is actually a lot of TTL configurations like mandates for example they technically not VCC connections you'd be like VBC like a base collectors and like that that irrespective it doesn't matter that's just where that came from now these days of course TTL's people dead know as a doornail so it should bye-bye but never mind because we switch to things like that which which a heck of a lot faster and in the case of field effect transistors fats are the common usages of EDD in the SS because in an effect we will have a gate and will have a drain on a source so VD is greater drain the SS sources also you see VCC VD VSS they know where they came from to Lego call type out moving right along so why on earth would you want to do this when I take a perfectly good analog signal perfectly good and say you know what I'm going to make a digital and then I guess the point and then transmit and redo the same reverse the other end it seems like you've given up a lot of like infinitesimal our value information in vastly small the information you thrown out the window and is gone while the other based on you to state conditions I guess the reason that it is good is because any noise that the analog signal picks up during between the transmission and reception can be cleaned up our provider bulges stay with invalid ranges of course and that would then lead to data corruption if it wasn't valid and that means that we can then take that at the other end and basically repeat the signal its original form and we can get rid of all the nice so we can overcome line loss and noise up to a point so when you got a digital connection of any kind you either can be limitations you place on that so we will will rate cables for example must say right well the cables gotta have certain characteristics otherwise you your maximum range of 100 m in some cases cheap cables like a cheap cat five cable sunlight that might struggle to take 10 100 ethernet are 100 m in ice able to say it's generically hundred metres but he really high-quality cable you probably get hundred 50 or hundred and 80 m where that is in feet in a 300 feet whatever so should get the goldplated vacuum sealed with built-in antivirus AI did the coal plaything on episode before so that's the heart no dealers and he's joking please do not buy goldplated anything thank you very much and help move not our only feel free to find if you want just don't expect anything out it will look nice though pretty very pretty dear that's pretty much it okay so the digital is good in the sense that we can recover noise are however the problem is that there is a range limitations because voltages can't be guaranteed to be in the same ranges from side to side but there is also other problems are that you get with digitising data Nassau by focusing on a bit so keenly of noise that's out the window we can regenerate the data fantastic but the thing is that beyond resistance which is an resistance is essentially just a nutshell is when electrons pass through a conductive material essentially as those electrons bump along are they will lose energy as the next one is bumps and exons by the maximum advance and that's just based on the number of free electrons they are and how attractive they are to the to the nucleus of whatever they're being bumped past if that makes any sense arm insofar as you know you can't beat resistance solicitor superconductor and that's another story but some anyway so I'm not at resistance I want to talk about the two other big bad while not big and bad in the sense of data transmission they are mass inductance and capacitance such as data transmission of the combat the high-heeled arm else was been partly switching inverters a worker in everyday absolutely cultural and data you wish your property arm for that as a topic for the future Sunday but wasn't absolutely but the moments for the moment data transmission so capacitance capacitance respect sure are so capacitance are cuticle CV stone out the basic want and away arm by our Soviet lawyers running side-by-side one with Kerry and the other with nine I will present capacitance between them sometimes, parasitic capacitance arm generosity is directly away a few away or gone over a ground plane as well are you will make capacitor however smile Arnold is a capacitance from our absolution as stone already absolution is a constant based on the material asses the service area endears the distance between the two wires are underway in the planning of the two planes arm so as you decrease the distance you'll get more capacitance if you increase the surface area you'll get more capacitance as well arm and diagnostic change in dielectric customers well to adjust the capacitance but usually in a circuit board at Sapphire for the four stands for the dielectric constant correct I think so but arm don't quote me yes we can look that up and confirm but appreciates what it is arm so capacitance will ruin your day because it will slow down your agents are expecting a nice clean in a transition from 0 to 110 and there is a lot of parasitic capacitance or your transistors have one capacitance in Oxnard and an infinite rise time we like to expected Mike to model it will you'll have some rhizome in the nanosecond range usually give-and-take arm faster if you doing really hasty larger but done yes of the capacitance will slow down instead of raising new and one nanosecond mediates 5678 more if it's really badly and crappy board layout arm and neck in factory transitions you know if you have a carcass can assemble your signal 5 ns after the signal goes high in your still slowly raising could be an undefined state that China talked about between your input high in your input low and new get some corruption of your downstream yes exactly our jump to the punchline and that's okay but I guess the thing is that our why it takes time white has that effect is that it's kind of I think it's is, think of it like arm if you want if your target is to reach so if you're filling a bucket with water and your targets voltage level is the top of that buckets then if you start out with her at with a track or a series of tracks and circuit board or in a cable wise in the cable and you put current through one of them what's can happen is it's going to take a little bit of time not long like you said nanoseconds perhaps in order for that current actually build up to that level and the top of the bucket that amount of time is you and that's what you'll see is your see that voltage rising right you'll see that level rising instead of going straight to their like a sharp edge like all the drawings and excellence would have you believe no it actually has a rise time and it's because the capacitance is you have to overcome that and fill that up before you actually reach your target so the thing about capacitance also is measured in farads and that's actually named after Michael Faraday and 1 F percent of one ferry capacitor is essentially one cool ohm of electrical charge and it has a potential of 1 V between the plates now I just realised that I then used cool ohm to describe farads which is not helping cool ohm is and I don't notice of my head I did write this down to 6.241 x 10 the 18 electrons worth of charge and that allows lights yeah if that sounds like a lot that's because it is so one ferry capacitor is that you note you don't have many of them right now that's another that's in the super Range yes that's crazy big so most the ones that we use and circuit boards and stuff or to our microfarads or less so in parasitic capacitance. In the pickle varied range exactly yeah various very low number picofarads per year as it authorises tender -12 yet exactly as a sort of thing that it that that's why you rise time is yoke for example if it is like hundred nanoseconds whatever it is it's because that capacitance is so low and the emo say okay shrug was the big deal out of it so like okay will get that minute and our knowledge of head too far so okay inductance who is kinda related to capacitance but in different way and is with inductance yet that's because when you flow current through a wire generates an electric field and if you then take that wiring behaves what was whited into a coil then that will actually create a much more intense electric field electromagnetic field and you know that present in inductance which is essentially as you're building that electric fields because matter that is the same matter is in innate material where that air whether that's you would water in a steel doesn't matter whether it is everything has a bike or permeability and that permeability is can resist arm the creation of an electric field in different materials will have different permeabilities so we generate elite electric field is not instantaneous just like capacitance same problem and once you've built up that electric field and if you turn the current off the field will then collapse in the funny thing is about that as the fill collapses it continues to drive the current for a short period of time so you sorta get this charger. And then feel collapsed. And that effect by Howell how much energy it takes to overcome that end & that's arm actually measured in the Henry's is acting a Dr Joseph Henry in the funny thing about that was that arm although he discovered inductance about the same kind of time as Michael Faraday was actually kind of more widely credited to Henry for some reason but if you really want to derive the equations for all this in any mention some of them before arm there is a link in the shadows to Maxwell's equations you know and they're all dry from that's if you want to go ahead and go and drive some equations you can in your own is an exercise to listen yeah exactly see how insane your feeling or in a whatever have fun okay so capacitance and inductance are essentially the dynamic components of a changing voltage when you're carrying a current together with a static component which is resistance they are collectively assessed and referred to as circuit impedance now I don't want to go any deeper than that suffice to say suffice it to say when you try to transmit digital information and power supplies but that's another story another story or episode with digital data transmission arm that is your enemy yes in an ideal world when you can to appoint safer low-speed digital media TTL level proper nitrogen can were some issues with it aren't new tender neglected parasitic capacitance and inductance in your circuit and just pretend it's not there in the early days didn't matter I mean you could lay your axe anyway you liked it didn't matter because the data was going past in the kill her to the low megahertz they didn't start to notice this art until about 20 years 25 years ago so in the earliest early days of electronic circuits and switching it was all just like we can do is make a fast year is a fast… PA crank up the clock speed you know but there rise time and the nanosecond that became Turner 100 ns didn't matter if you're working at kilohertz timescale that still infinitely fast for your purposes exactly right so you could model that you get away with this this simple beautiful straightforward picture of your line of your mind of the perfectly square our function with no rise time or essentially negligible rise time it wouldn't matter and is anyway so I guess I guess work as were so disturbed is to hold back this resection so as the BJ Teal offence which is on the voltage rises slow down by inductance new capacitance of the charge builds the electric field forms an activity you curved edge to the voltages arises and when it reaches the maximum and the same effect as it sort of slopes often curls off as a vultures turned off in the fields collapse and the charge dissipates and the faster you switch the more chances that you can actually switch before you reach that valid target voltages you mentioned about five minutes ago and that means that you can start corrupting your data for transmitting data from point A to point B you absolutely have to arm yet you absolutely have to know you're in a valid voltage range otherwise you've got nothing as a second time was you see in a week mention current edges you can also have the are the reverse problem where you get a very sharp edge and start ringing signs that it is coming up and stopping at 1 V five alts whatever you're working out the BCC are you could swing up to 67 V and come back down for a house in New York and ring out and settle eventually at 5 V and is just as much of a problem as E2 slower than average that's true very true so are because of overshoot and data and so on yes okay if you're transmitting data is getting back to transmitting data again from point A to point B arm it is necessary to have a way to differentiate between the gaps between a series of consecutive value select save got 11111 and zero you need to be able tell the difference having one that is and insane in the success of zeros me when you go from what is your is obvious the transition between them is clear so how do you do that the answer is you have a clock and the clock is guaranteed to turn on and off once arm every cycle wherever there is a bit so we sample a voltage of the transition points to extract the digital state at that point in time so owner steals my squid see terminology and undertook STA Nessie also now a single data signal arm clock LCL does your cloth get the ostensible being our associate STL so to wise one carries data one carries our clock and it sends data like this and eventually you reach a point where it's not possible to switch any faster because the impedance issues are preventing you from actually getting valid data from point A to point B now admittedly this sort of a problem was we are just as much of the time was a bit as much about BJ teas and CMOS switching speeds so I admit that it's not that the transition arm to what we talk about with with guard parallel cereal and so on and modelling it wasn't entirely driven by impedance issues because obviously you BJ teas on the way out CMOS vets are coming in yellow and obviously switching rates improved and that changed things as well so they were all consuming factors II admit this but anyway the initial thought was out of as previously on a previous episode was to go from a single data stream to multiple parallel paths in other words going from serial to parallel sides that are just clocking through one bit one guideline you would clock in like eight bits have an 8-bit bus or 16 bits or 32 or 64 128 whatever and I just think create a whole new problem because now you have to align each of those individual guidelines with the same clock so that created the problem of bus queue whereby you bid zero could arrive before bit 15 and when your clock through you would then start to get skewed data so then you get a clock skew relative to the bus lines and of course you have skew individual lines of the bus relative to the other lines on the bus anyway so it was around about this point where people started to realise that serial was actually a better way to go if you want to get high speed data from 1.8 to point B and they realised that we had to stop modelling or rather we had to stop ignoring our digital data lines are when we were doing modelling is ordinarily if you're designing analogue circuit you would model and you would control the impedance are of that asset attracts because you want to make sure that your impedance is matched on the whole Rouse and each end is a is a suite we did mention this in a previous episode on radios bite arm that already achieved is usually in impedance matched circuit now 50 ohms is pretty typical of 75 as well that's true absolutely right but in that the bad old days they never bothered sitting have to attend as it did matter but once you start going higher and higher frequency you cannot avoid this you can say to digital signal as much as you want the truth is that you have the capacity inductance will kill you you will not kill you literally will kill you signal and that's kind of when you're an analog or digital design it's the same thing as being kelp that sort of feels like you look at it is a very sad way form matrix is a great software development company whose apps do you guess that many tricks there apps include Butler chemo Leach desktop curtain time seemed Usher Moon name angler resolution later in which the summer to talk about the each app but they make so will just touch on some of the highlights of either of them which you should think about which is a supercharger the command tab apps which are if you got three or four documents open at once and anyone app then which is beautifully simple pop up quickly let you pick exactly the one that you're looking for name angler save got a whole bunch of files need to rename them quickly efficiently in huge numbers when they make these great creating stage renaming sequences with powerful pattern matching showing you the result as you go and if you mess it up just revert back to 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to overcome this problem with digital data transmission we actually had to wear the industry had to start modelling as an analog transmission line and that's when I come back to Everything is analogue so we're trying so desperately to convert information into digital to overcome the problems of noise which we then achieve but the more data we pushed through the farce to push it through we come back to analog modelling techniques to handle our digital data and the transition seems to be around about 100 MHz and I say roundabout because a lot of variables there is also the things you can do to try and extend a lot of further and tweak this and tweak dad and so on but inevitably around about the frequency we start giving up on parallel we start giving up on displaying tracks randomly or having tracks that are just precisely the same length so that it so you propagation delays are all the same and laying them out perfectly in parallel we do is give up on all of that and we to say know what I'm just going to go with a transmission line to strips and they are always the same gap sandwiched between exactly the same, planes arm and everything is completely impedance controlled from end to end and that is essentially when we start talking about what they have come to coin the phrase as high-speed serial so and white or red as previously was somewhat to about parallel ATA and serial ATA arm on episode 12 sober feedback that you will know more about the hard drives and solid-state drives and in their switch to high-speed serial for interconnecting so that severely a motherboard on those squiggly lines typically zero the memory as well and another one of its parallel serial after my head while not addressing lines but the point is that there's other issues as well with high speedos were quickly touch abound on my favourite one that that is annoyed me as jitter and the first time I saw jitter, blew my mind because I you have this idea that a clock is pure underwire thought that but you know whatever my brain thought I hear that's a clock so clocks are always on off 11 cycle ride that always the same period and they drift with time right forward or back likes there because they never if you say I've got a clock is exactly 100 MHz there is always 100 MHz maybes can be like 100.001 MHz as always gonna creep forward seven RTC real-time clock based on that frequency then it's going to drift ever so slightly with time when the first time I saw on a digital sampling oscilloscope and I saw the jitter on a high-speed clock, blew my mind to know have you seen jitter earlier please a big part in our switching regulators on the fees node which triggered purposes of this episode are as a digital signal between zero and whatever your input voltages kaleidoscope very sharp edges like the digital typing about and its office modesty and problems in capacitance inductance jitter in so the way that I've seen jitter on a DSO is that you're set the trigger level to yoga let's say you wet where the yard with the clock NCO rises up to to maximum your set that and lock at the centre of the screen and then you set your span such that you can actually see the width of that actual our pulse that clock pulse and if you can see that on the screen the yellow calf like half away form slowly more than half on each side of centre and you'll see the width of those of that of those clock periods changing a vessel like wobble layers I can turn under persistence feature to see publishing the check only edge yet that set so the clock it is not you may think a good period of like the 810 10 Lower Hutt 50 ns and like that or whatever it is and it's not you'll be like 49.1 and then it will be 50.2 and it will be 49.7 LB 50.1 and it's all over the place it's not exactly the same every single cycle and that's a big problem because if you're using that clock even if using high-speed theory of using the kind that clock to try and extract and recover your data you're in big trouble now because you can't be guaranteed you're actually sampling the right point you could be slightly behind slightly ahead and clock drift is simply the fact that your jitter will be predominantly positive or put on the negatives over a long period of time those those slight additions or slight subtractions will change the overall frequency and that will cause the drift so I just find you fascinating is first, a sophism of those Melton Mowbray others of the craziest thing in the world because it had this picture I had you clocks always gonna be precise is like no it's not fairly light a lot of money can get a very legitimate clock on the computer of Cheshire but if you zoom in far enough it still gonna have jitter in the UK is analogue AAA go right there everything is L roll credits order now and I wasted you did it know when not we're not done yet again just begun me and we could go on for hours but were not going to for the sake of our listeners arm mental well-being so okay arm so traditional are essential about our so now we come full circle one of the things that you can do to overcome this jitter problem and high-speed serial problem is we can actually start to encode the clock with the data and is at that point where would you like to talk about that such a encourage siding technique is yes dictating an ample room arm yesterday's very various ways you can encode your new digital larger card than your dad are the are the first in the most basic one is coldly a nine resort nine return to 0 arm services the extremely basic it's what you think about when you consider a digital larger calm transitions only occur when the logic bits change arm any nuclear requires a very accurate clerk in error detection to make sure doubters being are sent properly severe string of four zeros you'll just set it 0 V through 4 o'clock cycles and in transition to a wine whenever that comes along arm very errorprone that we said Erica Clarke arm simple in implementation and thought process by has its drawbacks so you can move to its cold eBay fees method of encoding in the state transition in a biface system happens at the end of every bedframe so larger Kaya seven additional transition in the mid bit and it allows for some Clarke information to be passed along with the datastream so if you want to send along a 00 a new circuit board you would send low plus high so suggesting 041 clock cycle you are transition hi arm or it could be in a high plus levels of he started a wine you transition to 0 mid clerk in servicing Lolo all seen with one wine you would say arm middle level high or high level. Where you started that I get that rate gap transcends right the transmission was clear and an adjuster you rambling for a listeners yet that's okay it's the the idea is that when we encode the clock with the data are it means that's you wet we guaranteed that it's going to be essentially synchronised and that means that it's it's it's funny though because it it tends to you would think that's wasteful and I guess it kind of is a little bit but at the same time and overcome that problem and then you can then crank the speed up even more so it yet and that's that's the ultimate goal is to go faster and sometimes you have to take a step back take a few steps forward and I guess that's the way to think about it and you you you are surveilling more transitions 400 serving lower level your low high or high level arm value you take away some of the error from clock SKU and gender and you using there is a definite transition here there is another bet were not just hanging out not knowing what the lines dealing yes exactly so you that's it exactly right are so Manchester encoding I think is so similar to biface correct yes you to look over shorter so it similar to biface and that you always get arm you are transition at the end of every bedframe light you structure your dad are in such a way that it always yields a DC value of 50% or happily between the splice site. Five alts arm the holy cities of the wine I was his marriage voltage of 2.5. Similarly if you're wonderful was the affable arm so this means is that the average power over a long period of time is constant regardless of the datastream arm and again the sea transitions occur happily between the bet timeframe arm so why would you want to seem average power are well it simplifies your new circuit design your receiver this is how I understand it. Transmitter you cannot you can buy city zero think you I know that's it is it is popular the bottom line though is that they're all different slightly different ways of implementing the same kind of idea which is to integrate the clock with the data and this is just that your wisdom and my bit level data transfer may be talking about are when you start to structure your likely packets of CRC is in and parroting all of the stuff among women tell me that but you know obviously also building more redundancy on top of that so that you can then you had identified that when data is gone astray in and so and so forth but not want to get into that is talk about the lowest level nitty-gritty note that's it and honestly I don't have to might also want to talk about I guess I just I find this whole thing the digital is our resort one as I was always a 1000 that is so completely false and once you get your head around that you can sort of understand that arm animal everything is is truly is analogue and it's a and and all the digital stuff that we that we play with all the software that is all the finer psyches are true is a false you all that. It's all built on it's a layer of layers of abstraction on top of the real world and in the real world everything is analogue gas and is a summary different techniques and you stuff to get over it are the other factor digital as night caught in court real our scenario I want one of my favourite sales like its channel equalisation which is arm we talked about but hundred megahertz J transmission error transmitting icicle acts cable and a chance at about 100 MHz Easter running and issues were nice pretty ones and zeros at night you so if you look at the unjustly building plight of the cable to get its frequency response your sister's role offers a low-pass filter at hundred megahertz in this example so with channel equalisation at the other end you have your receiver and you send out a test pulse see how it changes and configure a filter so that you and again at hundred megahertz and above to keep the channels cortical flat and it's really cool stuff yeah and actually beyond this channel equalisation it sort of makes you realise that one is refocused on lot so far just talk about this topic is the oh circuit boards are contractionary thing I did so to talk about cables but honestly cabling is the same sort of problem you know you and you and it's like it's most things so long as we use cables and wires and all acyl stuff too and I say always list for a specific reason is that all the stuff that we are talking about has to do with the problems associated with inductance and capacitance I haven't talked about optics and I know if I should make this a topic for another episode but honestly arm a lot of problems of cabling go away with optics but a whole different set of problems come onto the tape complex right so you things like bend radius things about starlike splices joints patch is all that stuff which is more analogous to resistance but you know you don't end and of course the fibre also like optics is also Gala problems a different interference in your wavelength division multiplexing and all the rubbish see know what another topic for another day but honestly it comes back to the cables and it's not about the plating on the end it's how accurate and how well-built the cable itself is and that's why you'll have like tight tolerances for Sex not say are easy get this cat five cable is not guaranteed to work over a 10 middle length at 10 our 10 gig so you cat five cable isn't rated to to run it one giggle 10 gig over a certain distance and that simply because the tolerances for capacitance and inductance on those twisted pairs inside the before pair structure of the four pair cable you that is not as tightly controlled on a five cat five cable go to cat 64 example and that's a much tighter spec and that is guaranteed to carry gigabit or 10 Gb over a spillover certain distance so that's why people say are well on the lay cat 60 cables now they're only plugged into an ethernet switch that is doing gigabit but I want to go 10 gig at some point so by laying these cables now sort of future proofing to appoint spot factor cables are now more expensive to get 60 are that it is an iconic at five that's just another example beyond the circuit board that people will deal with from day to day is if it was me and I was putting arm you are twisted pair copper through my house I get the more expensive high quality are cable designed right 10 gig on the presumption that at some point the next two or three years old five years the 10 gig switches can become more commonplace and then because they are better quality they can handle a high-speed serial data better they go arm Bill did everything else you want out of this or should we wrap it up lager I could add quite a bit however I'd be distressing and are my digital modelling knowledge is not good enough for that night Catherine Bollin in a case if you want to worry this you can reach me on Twitter and John Geagea or you can follow pragmatic show and to specifically see show announcements 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Duration 43 minutes and 41 seconds Direct Download

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Carmen Parisi

Carmen Parisi

Carmen is an Electrical Engineer working as an Application Engineer in analogue electronics and has a blog Fake EE Quips that he occasionally posts to. Carmen is also a co-host on The Engineering Commons podcast.

John Chidgey

John Chidgey

John is an Electrical, Instrumentation and Control Systems Engineer, software developer, podcaster, vocal actor and runs TechDistortion the Engineered Network and technical whitepapers at Control System Space. John is a Chartered Professional Engineer in both Electrical Engineering and Information, Telecommunications and Electronics Engineering (ITEE) and a semi-regular conference speaker.

John has produced and appeared on many podcasts including Pragmatic and Causality and is available for hire for Vocal Acting or advertising. He has experience and interest in HMI Design, Alarm Management, Cyber-security and Root Cause Analysis.

You can find him on the Fediverse sometimes called Pleroma or Mastodon.