QSI Equipment main page

(remember: links to sub-pages at the bottom of this page)

click to jump to the bottom


There is a LOT of information in the "tree" below this page. It's on several independent pages. If you try to skip to the end, you may spend more time than following the path I proffer.

First, a bit of education on an issue that confuses everyone will help you. There is a company called QSI Solutions and another company called QS Industries. Often people refer to "QSI" and that is ambiguous, and leads to confusion.

QSI, a.k.a QS Industries is an OEM, who only sells to manufacturers, and makes the specialized ASIC (Application Specific Integrated Circuit) that is the "brains" of the decoder. http://www.qsindustries.com/ They do not support the large scale decoders. (Recently they have done a little retail sales).

QSIS, a.k.a. QSI Solutions is a company who developed a large scale decoder using the ASIC from QSI. They sold the LS and the HO decoders retail. The company was started by Tony Parisi of Tony's Trains, then bought by Josh Shedaker, who instigated huge amounts of new features. The company is currently inactive, here's the old link for use by the Internet Wayback machine: http://shedaker.wixsite.com/shedaker


Over time, QSI has made many different decoders, although my main focus is on the large scale decoders, I have found that QSI has been poorly documented, and when trying to untangle all of this, I wound up trying to document, and I have downloaded all the smaller scale decoder files.

Each decoder has a unique hardware ID, which is important to note so that you don't try to load the wrong sound/firmware into a decoder. (The system won't allow you to do it anyway!)

Here is a list of what I know:

  • 1000 Quantum 1/1a - HO
  • 4000 Quantum 2, Revolution - Large Scale
  • 6000 Quantum 2, Revolution U - HO scale
  • xxxx Titan A  HO drop-in (don't know hardware number)
  • 7000 Quantum 2, Titan FX-U - HO Titan, also called Titan-U (there is a U/W variant with wires soldered to it)
  • 7002 Quantum 2, Titan FX-SD - Titan? what size?
  • 7021 Quantum 2, Titan FX-DO - O scale Titan - also called Titan-DO
  • 7022 Quantum 2, Titan Large Scale Titan

Click HERE to see pictures of these decoders / spotting guide

History: first large scale prototype development:

The original product was directed to be very plug and play. It came with many connectors on it, and came with cables that plugged into the various USA Trains locomotives, and handled the unique high and low voltages found in USAT locos, and even the bipolar red/green classification LEDs as well as the common cathode LED setup. It was a great idea, but apparently considered too expensive. I think giving that up was a mistake.

This product was never sold, but I had one with all the adapter cables for the different locos. It was truly plug and play. You can easily see all the many connectors to accomodate all the different connectors in a USAT loco.

usat qsi

Original QSI Revolution / Magnum

The original large scale product was actually called the Revolution (before Lewis Polk's Revolution Train Engineer). There was a "magnum" version, which is the same decoder plugged into a board that connected the pins to screw terminal connections for use in any loco that did not have the Aristo socket.

The unit is a sound system AND motor controller and also controls the headlight and backup light.

The "magnum adapter" has no components on it, it just brings the pins to screw terminals. Only one of the two connectors has anything wired to it. The second connector gives mechanical stability, and was for future expansion (although Aristo sometimes wired things to that second connector).

The QSI unit works in three different configurations:

    1. DCC from the track
    2. DCC from an optional radio receiver (compatible with Airwire throttles, and NCE Gwire throttles)
    3. DC from track (it could also be run by an on-board ESC that did not use PWM) Sounds can be controlled by sequences of track polarity reversals. More later.

The picture below is the QSI Revolution decoder:

You can see the pins at each end that match the Aristo socket. This is an earlier version with the orange PolySwitch on it. Newer models do not have this. You can remove it and put in a jumper if you wish. Larger locos were tripping this PolySwitch, it was rated at about 2.5 amps. The "power sipping" Aristo mallet can "sip" a lot more than was thought. There are other overcurrent protection circuits that make the PolySwitches unnecessary. 

The picture below show the "magnum" configuration, which is the SAME decoder in a socket with screw terminals.

Unfortunately, this picture has the screw terminals to the rear. They are in the green housing on the far end of the unit. Remember, the main board is the SAME no matter what you buy or use.

Again, many people have gotten the impression that there are different hardware versions, there is not, there is only one hardware version, the ones sold by Aristo are the same as everyone else's.

The unit has down-loadable sounds and is very configurable. There is a programmer that is needed to download different sound files. All other programming can be done by a normal DCC system, or through the AirWire transmitter (see below).  Some programming can also be done in DC mode, such as volume, etc.

In DC operation, using the reverse switch on a power pack will allow remote control of the bell and/or horn/whistle.

In addition, for DC operation, there is the "Quantum Engineer"  that goes in series with your DC power pack and the track. It allows a number of programming functions, volume, consisting, and remote control of 30 different sounds.

Basically the QSI unit is a very flexible DCC decoder that also will run on straight DC and will interface to AirWire transmitters. The unit automatically senses DC or DCC.

QSI large scale Titan

Tony worked on improving the unit, and the big improvements were more lighting outputs, higher current outputs, and used of an improved ASIC that does much much more. It also incorporates screw terminals for the connections:

 There are tons of lighting outputs, high current outputs for direct driving of the heating element in a smoke unit and the ability to pulse the smoke unit fan in synchronization with the locomotive drivers (autochuff) or a chuff switch.

A big feature is the "emulator" mode, which brings a unique level of authenticity to sounds, where the digital signal processing unit modifies the sounds to match load and other characteristics, as opposed to just playing a different sound loop, like the rest of the world's sound decoders.

More on sounds:

This system is one of the few that can read the actual load on the motor and change the sounds based on it. Some units like Phoenix will do a good job of "faking it" by sensing the track voltage, or motor voltage, but only a BEMF-based system can really sense the load on the motor. The QSI changes sounds based on load, so going up a grade with a heavy load will result in sharper and louder exhaust notes and less load will make them quieter, and drifting will make it almost silent, as per the prototype. Diesels will also exhibit changes in sounds based on load. 

There is also a command-able "Doppler shift" for the horn/whistle that simulates the change in frequency you would hear as a real train passed you.

The sounds (and the firmware) for the unit can be downloaded and customized with the programmer, about $90, which uses a USB interface on your computer (Windows only)

Once you have one sound file, you effectively have "everything" for that locomotive type, and you can change/customize, and save your customized files. At one time, there were many different sound files each with maybe a different horn, etc, but that quickly became too much for Aristo and QSI, so download ANY sound file into any pre-programmed decoder and then swap the horns, bell, etc.

Note that the Revolution sound files are different from the Titan sound files.

The Titan also works with "ET" sound files, Emulator Technology, where the decoder actually modifies sounds with a digital signal processor (DSP) to match load, engine wear, temperature, etc. It's like an airplane flight simulator. The effect is beyond all other conventional "sound loop" technologies.

Typical decoders just increase the volume to simulate heavy load, where the DSP in a Titan can modify the sound like the real thing. This is especially evident in chuffs on steamers.

Current handling:

This is always a concern in G scale. From the very early days of DCC for large scale, we have been told we need a lot of amperage, that the stall currents of locos can grow to 30 amps.

I think that while you can make a loco use a lot of amps, but in normal running, most locos run 2-3 amps under a heavy load.

So, when the QSI Revolution came out, there was a lot of talk about it's capacity. I heard (not read) 2.5, 2.7 and 3 amps. It does not have big heat sinks, and I was very concerned.

The output transistors are rated at 5 amps, but heat dissipation will shut down the system at loads that high. For some people who have the decoders where there is a heavy load AND a big loco AND no air circulation AND a hot climate, thermal shutdown has been experienced. A small fan blowing air over the board will mitigate this situation. (This is not uncommon in the large scale world)

It turns out that the QSI has a good tolerance for high loads, and an on-board temperature sensor. I had no problems initially with any loco, but after starting to put loads on my locos, I had a few problems. So did another friend, Leonard Kerns, both of us were getting the power cutting out on the Aristo mallet.

Well, we checked temperatures, and there was some funny stuff going on. I did find that the 2.5 amp PolySwitch was bent over the output transistors, and it "got" some of their heat. The bottom line was that the PolySwitch was tripping prematurely. We bypassed it and not a lick of trouble since.

The later production QSI Revolution boards no longer have the PolySwitch, if you have one, remove it and put a solid wire jumper in it's place.

The lighting portion of the board for the Aristo locomotives has a 1 amp maximum capability, but (from their engineer) this means that incandescent bulbs need to be about 100 ma or less since they have about a 10:1 surge current.

The Titan has no such limitations, and will handle about 6 amps continuously, and 10 if you have a small fan. The output transistors can handle 60 amps peak.

Interfacing a smoke unit:

If you want to use a smoke unit that has a "chuff input", the recommendation is to use an optical coupler with an open collector output. Get one whose input diode can handle the current from the fan unit. Put the fan through this, plus to coupler to fan to chuff switch to ground. Now connect the collector to P2 pin2 and the emitter to P2 Pin 1. Connect the "rest" of the smoke unit to track power.

I recommend using the "direct drive" capability, where the decoder drives the heater and fan directly and separately. The decoder pulses the fan for you in time with the chuff. Very realistic!

This is described in subsequent pages.

More on DC Mode:

Basically the QSI will run in many modes. In DC it runs fine, but you have to remember if you bring the voltage to zero the sounds stop. It has a microprocessor that needs power. The loco stops moving around 7-9 volts, the decoder turns off below that.

So, you just slow down until the loco stops moving, and everything will be fine. If you really dislike this, or are running an Aristo TE system that insists on reducing voltage to 0 before reversing, get the "super cap" add on, basically a small capacitor that stores enough voltage to keep the micro and sounds running for about 20 seconds with power removed.

Turn the Bell on with a Quick flip-and-back operation of the direction switch. Turn it back off by doing this again.

A fast reverse starts the bell, do it again the bell stops. Ray Shoop tells me that the bell trigger is 175 milliseconds, or under 2 tenths of a second.

Reversing the direction of the loco while it is moving starts the horn/whistle, and turning it back stops the horn/whistle. The direction of the loco will not change. It only changes after you bring it to a stop.

So with a "normal" reversing switch, you can control the bell and the horn/whistle.

Note: If you do a Slow flip-and-back operation, you will get a short Whistle hoot instead of the Bell. If you try to do a very short
Whistle blast using a Quick operation, you will activate the Bell instead.

Another option on DC is the Quantum Engineer shown below. You put this between the power supply and the rails and it will let you control all the sound functions, it has a bunch of buttons for each sound. It can control 30 sounds! (It basically does sequences of polarity reversals)

Unfortunately this box has a max of 2.5 amps, and will run to about 3.5 amps, so only one loco per track.

There is a booster which has a 40 amp capacity, but it is $200. I have one and it works well.

More on AirWire mode:

You can run the QSI Revolution or Titan on battery (or track power) and control it from an AirWire transmitter. There is also a "GWire" transmitter made by NCE that is compatible.

All the AirWire transmitters will work, but there are some limitations and caveats.

Read this page that is specifically on the QSI and AirWire, which also speaks to the NCE GWire throttle

To be used with the AirWire transmitter,you add a GWire receiver. It connects to the Revolution or Titan decoders by a small flat/flex 5 conductor cable.



Click the links below to go "deeper" into details on Individual topics, the most important starting places are at the beginning.

  QSI Decoder Installation Tips    QSI Titan   QSI Revolution / Magnum
  Software programs & basic setup
  QSI Programmer H/W & S/W Overview   Installing the programmer & driver    QSI firmware/sound File Programming   AirWire & Gwire operation   
  Titan sound files    Revolution sound files   
  Decoder programming    
  QSI DCC Programming Tips   QSI Titan lighting effects    
  Original USAT Prototype   QSI "Cheat Sheet"   QSI hardware pictures     QSI programming fixtures 
  QSI Product history  QSI Titan versions    Titan smoke   
Weather Underground PWS KCACARLS78