1. #1
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    Default Multiplexing - No stupid questions...

    Is there someone out there who can explain the multiplexing concept to me? We haven't got a multiplexed rig, but the time will come...

    I've inferred from the reading I've done that it is a common 'bus' for power on the rig. Is it that simple? A thick + wire that everything is tapped into?

    Or is there more to it?

    Saw an ad recently in FH mag for a hydraulic multiplex generator.... (??? WTF ??? )

    Thanks for your explainations. Please use small words.

    Randy
    SRFD905 - Serving since 1998

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    Default Multiplex

    Bare bones of the systems I am familiar with is this:

    Standard wiring systems use a wire for every light, switch, and electrical device. Multiplexing consists of one wire carrying mutliple signals to provide power to multiple devices, thus reducing the number of wires in a truck. Also when a truck is multiplexed it can be easier to determine electrical problems. Everything is customizable on a multiplexed rig. I know there are going to be people on here who say that multiplexing is a horrible thing and that it makes the trucks too complex, let them have there opinions. Personally I would reccomend the Class One system, it has been around for a few years and most of the bugs are worked out. If used right and used on a single source truck (manufacturer makes the cab and chassis themselves) it can be a great system. Just my 2 cents

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    Multiplexing is becoming very popular on trucks and eventually will be the norm. Like Jake said, it is very customizable and the options of what you want to do with it are pretty much endless.

    With multiplexing, the truck is split up into different nodes which are located throughout the chassis and the body. All the different devices hook to a node and there is a cable that runs from the node to the brains. So instead of running a different wire for each warning light to the master switch panel, they are hooked into a pin on the node. If there are emercency lights hooked to pins 1, 2, 3 on node 8 - - Pins 1, 2, 3 on node 8 are activated when the the operator turns on the Mater Warning Light button the control panel. The system is very scalable so you could do quite a bit with it.

    I have seen both the Class 1 and the Weldon. I personally like the Weldon system. It is very easy to use with a nice color screen which can be used for up to 3 video inputs such as side and rear cameras.

    Single source has nothing to do with this. Spartan uses Weldon and when the body manufactuer starts building on the truck, all they do is add on to the system by adding nodes, connect the wires and program the system.

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    Default Multiplexing

    I'm not a big fan of multiplexing for one simple reason; a problem usually results in a catastrophic failure. We encourage our clients to avoid it.

    East West Fire Apparatus Consultants Inc.
    Apparatus Design Specialists
    866-843-1075
    www.ewfac.com

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    Default Consultant ???

    Well, here we go. This last comment just reinforces my theory that consultants are people who collect a fee from someone else in order to share their opinions, whether fact-based or not.

    In this case, quite the opposite is true....multiplexing ACTUALLY makes a problem easier to diagnose and rectify. Got a phone in your house or business? Well, its multiplexed. When's the last time it didn't work? Catastrophic failure due to the fact its multiplexed? Show me case history...then I'll give your statement some merit.

    Major emergency vehicle manufacturers are using multiplexing and it works quite well. Remember, Freightliner, International and many other truck manufacturers use it in HUNDREDS of THOUSANDS of vehicles because its STATE-OF-THE-ART technology. If its good enough for the operators driving thousands of miles a year, it oughtta be good enough for us.

    Advising your customers to stay away from it? Must be you have stock in horse-and-buggy companies. Otherwise, your fact-devoid advise is deprivivg your "clients" of the latest development in electrical system technology.

    Why do some Fire Service "consultants" see the need to buck advancements when they exist for their clients own good? Please give the intelligent consumers in our field some credit.

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    Default Multi-Plexing Pro-Con

    The advent of Multi-Plexing has been around for a number of years and was initially used in the Transit Coach business. Yes there have been problems with probably ALL of them at one time or another BUT these can be quickly corrected and resolved easier than the old style way of having to trace wires or "wonder" where the problem is.

    I can speak for using the Weldon system (now owned by Akron Brass) and it's in service with a number of FD's both large and small throughout North America. (Dallas, Fort Worth, Charlotte, Riverside County CA (50+) Edmonton and Calgary in Canada and I've talked to the mechanics who've worked on them and they said they wouldn't go back to the old style system.

    Spartan looked long and hard at both systems and went with the Weldon ilo of Class 1 and ALF now offers the Weldon and Pierce have their own which is proprietary to them and it's a Master Slave verses the Weldon which is a Peer to Peer.

    The major issue is to ensure the builder your looking at "has" experience with them in having built and delivered a number of trucks. The features and advantages far outweigh the disadvantages IMHO and you can reprogram it to make changes to controls etc.

    The Weldon V-MUX color display is great too as you can incorporate a backup and RH side view camera as well as a easier control of all the switches compared to the conventional style. Finally the old problem of the "Door Ajar" light and which door is ajar is easier to identify because the builder can show a schematic of the apparatus and indicate which door is ajar at a glance.

    Finally the car and truck manufacturers are using multiplexing so it's only a matter of time so better to be the flow and although there are sometimes a problem they can be easily solved IF the builder has the knowledgeable people to assist a FD mechanic in a situation.

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    Default

    Quote Originally Posted by toddmcbr
    With multiplexing, the truck is split up into different nodes which are located throughout the chassis and the body. All the different devices hook to a node and there is a cable that runs from the node to the brains. So instead of running a different wire for each warning light to the master switch panel, they are hooked into a pin on the node. If there are emercency lights hooked to pins 1, 2, 3 on node 8 - - Pins 1, 2, 3 on node 8 are activated when the the operator turns on the Mater Warning Light button the control panel. The system is very scalable so you could do quite a bit with it.

    I want to be sure I understand this correctly.

    Power +12v is run out to a node.
    A node has serveral 'channels' it can turn on and off
    A node would listen to a central processor for control signals, and provide feeback about the status of each 'channel'

    Correct?

    Also, what is the signaling mechanism between the controller and the nodes? A digital signal I would assume?

    Also, thanks for the insight regarding your experience with the multiplexed systems.

    Randy
    SRFD905 - Serving since 1998

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    Default

    My opinions on multiplexing are pretty well known.Horse and buggy days? Well,I don't want to go back that far,but I never had a rig with a mechanical connection between the throttle and the fuel control fail.Can't say the same about the electronic ones.Same with multiplexing.After it's been in ACTIVE fire service across the board for 10 or so years(withou problems),I'll get a little more excited about it.Easier to repair? Ah,yes and no.Simple programming,module issues may be easier but other issues will be like any other computer with a problem,intermittant and HARD to find.For me,I still don't have a problem with a piece of wire,pretty easy to find and repair faults here.But I remain open to 'plexing,once the "bugs" are worked out. T.C.

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    Default multiplex

    As those for the multiplex system have said; if it is correctly installed it is the greatest thing since sliced bread. Well, unless the manufacturers have developed some intelligent installers along the way I'm not totally convinced. Problems with units dying, you bet and at the worst possible times. LED screens that are obliterated because they did not account for the 110-120 degree sunlight for the Southwest. Over the road truckers and cars for the public are fine because they are not cobbled into by the after market people cobbling up the wiring. As for custom builders of chassis up makers they have their share of glitches too. Circuit boards, computers, relays, relay and circuit breaker panels, and anything else they can subject to water, vibration and the endless other things that can deteriate or come undone are the problems I see. Diagnostics through a long, very long phone cable with a lap top to talk to the factory, expensive diagnostic discs from the factories, yada, yada and so forth. We even had one guy at work that bought a brand new car that totally died at 300 miles due to multiplexing. They could not figure it out at the dealer so gave him another car. Yeh, great. I would not say that the diagnostics are all that great either. When technology becomes bullit proof I'll buy it. My personal vehicle is a 73 Ford truck with no computers and it gives me far less trouble than the wifes 2004 van.

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    Quote Originally Posted by HFD147
    Well, here we go. This last comment just reinforces my theory that consultants are people who collect a fee from someone else in order to share their opinions, whether fact-based or not.

    In this case, quite the opposite is true....multiplexing ACTUALLY makes a problem easier to diagnose and rectify. Got a phone in your house or business? Well, its multiplexed. When's the last time it didn't work? Catastrophic failure due to the fact its multiplexed? Show me case history...then I'll give your statement some merit.

    Major emergency vehicle manufacturers are using multiplexing and it works quite well. Remember, Freightliner, International and many other truck manufacturers use it in HUNDREDS of THOUSANDS of vehicles because its STATE-OF-THE-ART technology. If its good enough for the operators driving thousands of miles a year, it oughtta be good enough for us.

    Advising your customers to stay away from it? Must be you have stock in horse-and-buggy companies. Otherwise, your fact-devoid advise is deprivivg your "clients" of the latest development in electrical system technology.

    Why do some Fire Service "consultants" see the need to buck advancements when they exist for their clients own good? Please give the intelligent consumers in our field some credit.
    Well, seems as though we've hit a nerve. No, we don't have "stock" in any horse and buggy companies. What we do have is "many" years of experience in designing apparatus and many satisfied clients. If a client wants multiplexing in their apparatus then they will have it. If they ask us our advice, we advise them that we're not totally comfortable with the technology just yet, and let them decide. We do not strong arm our clients into what they choose. True, multiplexing has improved since it's inception. However, there are still issues that we have seen that should be considered. To compare over-the-road trucks to fire apparatus as an example just proves your inexperience. Finally, we are advocates of new technology. We do seminars on "Looking to the Future" when specifying new apparatus. The Telma retarder is a huge acheivement over the Jake Brake. So, I'm sorry your so upset by what we said about multiplexing. It still is our professional opinion that it needs improvement. If your not in agreement then thats your option and you need not "pay us a fee".

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    Red face Multiplexing

    Im an ASE certified mechanic for the Ohio Dept. of Transportation, we have several multiplexed vehicles(Intl. dump trucks). I as a mechanic feel that multiplexing is good from a service stand point, however there also many negatives to it as well.
    The drawbacks to mulltiplexing are, you have to have a special scan tool in order to troubleshoot any electrical trouble, no more simplie test light checkouts, but the computer tool does save time and many headaches!!! The other problem I have encountered is, when you build a chassis, you have to spec. exactly what elect. items will be used on the truck; strobes, radios, defrost fans, etc. Which is a real pain, no room for expansion without alot of $$money$$(new computer).
    All in all though I feel that it is very beneficial to upgrade when you purchase a new truck, keyword in that statement was I, you need to talk to your local servcice center and see what they say, I feel it benefits the service dept. the most.

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    Default New Technology

    How many times over our lives have we heard that a new technology was going to be the downfall of the Nation if not the whole Universe? The only part of new technology that bothers most people is the "NEW" part. Yes it means that the vehicle operators, and Techs have to learn "new" skills, and buy "new" tools, and of course "new" usually cost more. As time goes by the "new" wears off and what was once new technology will eventually be the norm.

    If a fighter jet can "fly by wire" at the speed of sound I can't imagine why a Fire Truck can't operate by it. The technology is fairly new to the Fire industry, and it will simply take some getting used to.

    Take care, and be SAFE.

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    Default

    Ask any military jet crew chief how many hours of maintainence is required for every hour of flight and you might be suprised. Just because something is new doesn't mean you should use it! I think your situation and your truck will dictate what type of electrical system you should have.

    Simple truck = standard wiring
    Complicated tuck = might consider multiplexing
    Dedicated maintainence staff = better chance of success with multiplexing
    Limited maintainence staff = probably should stay with standard wiring

    People bitch why trucks cost so much; yet turn around and load them down with a bunch of crap that has nothing to do with getting the job done.

    Smaller departments need a rock solid truck that will give them many (30+) years of service. Multiplexing a tanker or brushtruck is about the dumbest thing I've heard off people doing.

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    Default Apparatus/Ambulance Dealer

    Compare Body Builder Warranties Multiplex Vs Hardwire there is usually a bid difference also compare exceptions and whats covered in the warranties

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    Default

    Thanks All for your input.

    Just for the record. I'm not in the market to buy a new truck.

    Is there a training document available online somewhere which outlines operations of the systems? I think I've got a pretty good grasp of the concept, I would like to understand the 1's and 0's of the implementation a bit. ( I work as a network engineer in my day job )

    Any of you wrenches out there have refference docs online you can share?

    Randy
    SRFD905 - Serving since 1998

    *~-|EGH|FTM|-~*

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    Default multi-plexing

    If you go to class1.com

    Under manuals, pull up the manual on the ES-KEY/USM Network. It tells you about everything you want to know.

    A little to dry of reading for my taste.

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    Default

    Bingo. Just what I was looking for.

    The key was finding about about the communication protocol, and the types of control boards. relay and solid state.

    Thanks much. I'll go away and chew on this for a while.


    The Class1 ES-Key TM System consists of several components that can be used in a vehicle
    electrical system. The system is multiplexed using the Controller Area Network bus and the
    SAE J-1939 protocol. An electrical database is used by the Control Module to operate the
    vehicle electrical system. The ES-Key TM Express software allows you to create, read or modify
    this database. Troubleshooting of the system is also accomplished with the software.
    The Controller Area Network (CAN) has specific requirements that should be met for
    maximum reliability.
    Network modules communicate with each other through the J-1939 Controller Area Network.
    Network

    There can be up to 16 Power Distribution Modules (PDM) in a system. The PDMís control the
    loads in a circuit. They come in two basic types, electromechanical (relay boards) and electronic
    (solid state). They can handle from 7.5 amps up to 40 amps dependent on the exact
    module specified. One of these modules is configured as an 8 input, 8 output, 4 motor driver
    (H-bridge). A low current (250 mA) 16 Output Module is available for use in indicator or driver
    circuits. The 16 output module comes in a variety of lowside and highside driver configurations.
    (Power or Ground outputs)
    There can also be up to 16 Switch Input Modules (SIM) in a system. These come in either 16
    positive input or 16 polarity selectable input versions. Any switch or input in the system needs
    to be tied to an input circuit on a module in the system.
    Vocation Modules are available for interlocking and engine control tasks. These are enginetransmission
    specific and there can only be one in a system.
    A data logger is available that stores system fault and interlock information. It can aso be
    configured to log specified circuit information. It will store 200 system faults and 6,000 events
    before it loops around and overwrites the oldest data. These events are all dated and time
    stamped to the nearest second. Up to 32 circuits can be tied to the data logger for troubleshooting
    or information purposes. It is also a true time clock and a temperature sensor can
    be wired into it. The time is displayed on the data logger. The temperature and time are
    displayed on the Display Module.
    There are variations of some of the above modules available.
    SRFD905 - Serving since 1998

    *~-|EGH|FTM|-~*

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    Default To clarify.......

    EWFAC1075: First off, you didn't hit a nerve. Those that know me also know that I will challenge anyone who uses a "business" to exert opinions without facts. That's all I meant in my response to your post.

    Secondly, to clarify further: I have been associated with the Fire Service for 35 years, doing everything from grunt firefighter to apparatus mechanic to officer to training officer, blah, blah, blah. I have also worked on dozens of truck committees. So my comparison to over-the-road truck's multiplexing systems was certainly not based on "inexperience", thank you. You however have not presented any evidence to support your OPINION that fire apparatus multiplexing isn't within your comfort zone. Why? If you advised some customers to go with it, and then they had problems, then I could see your not being too willing to advise someone to get it. Is that the case? Or are you just not understanding the technology? Lots of things are multiplexed today, and the manufacturers are constantly striving to improve on what they have developed.

    So, bottom line is: I don't agree with your advising "clients" against it, and that's based on my knowledge of the technology, not my opinion.

    I would only ask, when you advise against multiplexing, what do you use for documentation to support that position? Sooner or later, you'll run into an educated consumer who will ask just that and back you into a corner......

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    Default The Problem with Technology IS YOU!


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    Quote Originally Posted by HFD147
    EWFAC1075: First off, you didn't hit a nerve. Those that know me also know that I will challenge anyone who uses a "business" to exert opinions without facts. That's all I meant in my response to your post.

    Secondly, to clarify further: I have been associated with the Fire Service for 35 years, doing everything from grunt firefighter to apparatus mechanic to officer to training officer, blah, blah, blah. I have also worked on dozens of truck committees. So my comparison to over-the-road truck's multiplexing systems was certainly not based on "inexperience", thank you. You however have not presented any evidence to support your OPINION that fire apparatus multiplexing isn't within your comfort zone. Why? If you advised some customers to go with it, and then they had problems, then I could see your not being too willing to advise someone to get it. Is that the case? Or are you just not understanding the technology? Lots of things are multiplexed today, and the manufacturers are constantly striving to improve on what they have developed.

    So, bottom line is: I don't agree with your advising "clients" against it, and that's based on my knowledge of the technology, not my opinion.

    I would only ask, when you advise against multiplexing, what do you use for documentation to support that position? Sooner or later, you'll run into an educated consumer who will ask just that and back you into a corner......
    Sir: I will not get into a back and forth with you on this forum. You have your opinion and we have ours. You can go to our website www.ewfac.com and view our (experience) credentials. I do not need to explain or justify anything to you. Besides, you took the first swing at us because you didn't agree with what I stated in my original post. Whatever your goal is here I'm not the least bit interested in it. This thread is full of both those who agree and disagree with the technology, but I don't see you debating it with anybody but us. Clearly, you have an "issue" with consultants as demonstrated in your previous posts. I thank you for your concern that we will eventually run into an "educated consumer" as you put it, which is condescending to everyone in the fire service, but I guess I should really be thankful that you will not be calling on us. You have yourself a nice day!

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    Default

    Quote Originally Posted by RetJaxFF
    How many times over our lives have we heard that a new technology was going to be the downfall of the Nation if not the whole Universe? The only part of new technology that bothers most people is the "NEW" part. Yes it means that the vehicle operators, and Techs have to learn "new" skills, and buy "new" tools, and of course "new" usually cost more. As time goes by the "new" wears off and what was once new technology will eventually be the norm.

    If a fighter jet can "fly by wire" at the speed of sound I can't imagine why a Fire Truck can't operate by it. The technology is fairly new to the Fire industry, and it will simply take some getting used to.

    Take care, and be SAFE.
    Yes, but they have figured out how to keep the planes from shutting down. Not there yet with fire apparatus.

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    Quote Originally Posted by oldman21220
    Yes, but they have figured out how to keep the planes from shutting down. Not there yet with fire apparatus.

    This is actually not true and I hope I can explain this.

    Multiplexing has nothing to do with apparatus shutting down. People will often say "My KME shut down because of some sensor and the multiplexing". The multiplex system is PROGRAMMED BY A HUMAN to shut down the truck when that sensors status changes. If the sensor fails, truck shuts down. VERY STUPID. More logical would be to set of an alarm that the operator can CHOOSE to follow or ignore.

    Multiplexing can be explained very simply. There are "inputs" and there are "outputs". When they talk about a computer, its not like your PC. Its a dedicated connection between the inputs and outputs who's sole job is to make it work, and they DO NOT fail.

    Multiplexing input boards "scan" their inputs say 5 times per second. When you press an air horn button, it sees that. At the end of its scan, it tells the computer a status of everything, such as:

    "Heads up here it comes"
    Input 1 ON
    Input 2 OFF
    Input 3 ON
    etc.
    "OK I'm done"

    This message is sent 5-500 times per second depending on the system. So unless you can press a button 500 times (or even 5) in a second, the system will seem transparent.

    The "computer" sees these. It knows input one is the air horn button(and it doesnt have to know that), but it DOES have to know that when that is on, it should activate output 1 on board #whatever. You end up with a ton of controls that only need a few wires to connect to the computer. The controls go to the input boards, which tell the computer what is on and what is off. The computer knows (based on its programming) what to do with that information.

    Its so simple. Imagine yourself with a 2 way radio in your hand standing at a circuit breaker panel in the basement, and a buddy with a light plugged in on the second floor. He essentially has remote control of the breakers in the basement through you. Kinda the same thing.

    Sometimes, computers are told (wig wags are a great example) that if the light is requested to operate, don't let it come on as long as the parking brake is set (NFPA). So it happens. Traditionally, a relay is required to make that happen.

    I fail to see where the problems come in with the equipment. Some (ok many) manufacturers use multiplexing to make the trucks do what they want, where with traditional wiring, the same features are hard to do. Such as aerials that depend on 12 different sensors to work. Thats just stupid. Can you say idiot-light?

    Every engine made today is internally multiplexed. Nobody is complaining about them? Every transmission is too. Complaints? Their multiplex systems can be connected together for an integrated package. Complaints?

    Most pipe organs are multiplexed. Most phone systems are multiplexed. Most video poker games are multiplexed. Most pinball machines are multiplexed. All fire alarms are multiplexed. Burgular alarms, office phone systems, your car, etc.

    The trick? LEARN HOW TO WORK ON IT.

    EXAMPLE:
    If the perimeter lights under my pierce stop working, I go into the screen at the drivers seat and look at a few things. The screen tells me if the button that is requesting them is actually doing it. If not, I need a new button. Suppose it said that the button was requesting. Then, I go and see if the output is turned on. 99 out of 100 times, it is. IF its not, it never was. They dont "change their mind". They can't alter their own programming. If its requested, and there is nothing in there telling it NOT to do it, the computer WILL turn it on. So then I go to the module listed (right on the screen), right to the output (its listed on the screen - it tells you where to measure for voltage). Is there voltage there? If not, you need a new output module (rare). Then you troubleshoot the traditional wiring that goes to the lights.

    A multiplex compatible generator means that the computer can directly tell it to turn on without the computer putting out a dedicated circuit/signal and the generator watching for that dedicated circuit/signal. The generator would (in theory) be able to report back such things as oil pressure, oil temperature, voltage, frequency, current draw, etc. all for display on a screen in the cab, right with everything else. Neat huh?


    I hope some of this made sense.
    Jon

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    Default multi-plexing

    Unbeknownst to many in the fire service, many of the telescopic tower ladders have had multi-plex electrical aerial controls for around 20 years. Instead of having to run 20 - 30 wires up a 85 - 95 - 100' tower ladder, four wires, hot, ground, and two control wires will do the same thing. Most of the units equipped with this arrangement that I am familiar with have been very reliable.

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    Default

    chiefeng7: thank you for posting that explaination. It was my point all along that this new technology needs to be UNDERSTOOD before it can be embraced. Multiplexing is not going to go away. As I stated before, Freightliner, International and a host of other truck manufacturers have made systems that are highly reliable. That's not good enough for the Fire Service? Why not? Until there is an electrical engineer or multiplex service technician on every purchasing committee, the burden of helping the customer understand it falls to the sales professional or consultant. As I also stated before, once it is clearly understood, what basis would anybody have to not want the technology?

    I appreciate your willingness to help out the brothers in our business with facts.

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    Engine control complaints? Tranny control complaints? YES AND YES,like an Allison that downshifts from fifth to second or third whenever it feels like it(nice on ice).Or an ECC engine that returns itself to idle in the middle of a serious working fire. NEVER have I had either condition on a MECHANICALLY controlled system.Is multiplexing going away? Nope. As reliable as mechanical systems? Not yet and probably never. Do I understand it? I don't build 'em but I work on stuff run by them everyday. And they suffer the same ills as ANYTHING run by electrons.Ghosts,intermittents and some flat out failures.It's all a living to me so I don't care what you buy.We fix both mechanical and electronic systems.We also run a Towing and recovery service.Guess how many of my working fleet are multiplexed? One,my personal pickup. The working fleet are ALL mechanical systems,every one.No electronics and no computer controlled transmissions.Just stuff that will start and go to work on a moments notice,every time. Will I have a "plexer"? Nope,what I own will work for me well thru retirement which isn't far off. NOTHING you can buy today is as reliable as say an old 70's Mack or equivalent.And I don't care who builds it.As the electronics increase,the reliability decreases. Sad but true. T.C.

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