From the earliest days of Model Railroading, the idea of being able to operate trains in a prototypical manner was pursued. Advances included direct current power, solid state electronics enhancing operation with features like pulse power, and other innovations. The wiring would evolve to include complex block systems. With all these advances, the ability to control the locomotive, not the track, eluded everyone.
A number of innovations appeared over the years, starting in the 1940s, but it was not until the appearance of low cost microprocessors did modern Digital Command Control appear. A number of command control systems were offered over the years, many had serious limitations, such as the number of channels, or expensive components. Many were proprietary systems with limited support and expansion capability.
The path to Digital Command Control began when the NMRA decided to look at creating a standard for command control, to tame the confusion and fragmentation in the market. Early on, the members on the committee settled on digital as the preferred technology, instead of the prevailing analog systems on the market at the time.
Read on for more info on the systems that were the predecessors of the NMRA Digital Command Control standard.
The History of Digital Command Control
History of how Digital Command Control came to be.
In this article the term channel used by command control systems would be equivalent to Digital Command Control's concept of addresses. Unlike DCC, the channels used by a command control system were often usually fixed, often at manufacture. The Hornby Zero 1 system offered user programmed addresses, as it was a true digital system.
Many of the command control systems mentioned were analog in nature, using phase modulation, frequency modulation or audio tones to transmit commands to a decoder or receiver. For simplification, the term decoder refers to the electronics (the receiver) installed in the locomotive, that respond to signals from the control system. This is the reason behind the term channel, as a specific frequency is used to control a specific decoder tuned to that channel. Same idea as tuning your radio receiver to the station you want to listen to.
Note: All references to prices are in US dollars, and the date is in brackets. Many are from 1979. For comparison, $100 in 1979 is equivalent to about $290 today (by CPI, 2008).
The Early Systems
The idea of independent control of two locomotives goes back a long way. During the 1940s Lionel offered a system which employed a tuned circuit. A high frequency signal, created by an oscillator in the power pack, would control the direction of the locomotive. The locomotive would only react to the correct frequency, determined by the tuned circuit. Due to the nature of the electronics available in those days, the system was expensive and unreliable. Beginning in the late 1940s a new idea began to take hold, Progressive Cab Control, which was very complex to implement, and costly to construct and wire.
Advances in electronics, with the advent of cheaper, smaller and more reliable solid state devices, made even more things possible. It would take about 30 years for command control systems to go from analog to digital in the form of Digital Command Control. The shift from the analog computer to the digital computer drove electronics to the present day's powerful but small microprocessors that make Digital Command Control possible.
Lionel Magic Electrol
In 1940, Lionel offered a new product called Magic Electrol, installed in a locomotive.
Inside every Lionel locomotive is a device called the E-Unit, that controlled direction. The E-Unit was described as a solenoid operated rotary sequence switch. The Magic Electrol was used to control the E-unit. This allowed you to run two locomotives in opposite directions on the same track. Remember, Lionel used alternating current, so there was no way to flip the polarity. The E-Unit was originally developed by Ives, but lived on when Lionel took over Ives.
Instead of the usual method of controlling the E-Unit, where you cut track power to switch the E-Unit (forward-neutral-reverse-neutral) by pressing button 1, pressing button two (whistle) injected Direct Current onto the track that triggered the Magic Electrol unit.
After the US joined everyone else fighting the Second World War, Lionel ceased production of trains and Magic Electrol in 1942. But, Lionel wasn't finished yet.
See a Lionel ad mentioning two trains on one track
Lionel Electronic Control
The Lionel Electronic Train Control system consists of a one watt transmitter and a number of small receivers mounted under or within a piece of rolling stock.
The system first appeared as the 4109WS Lionel Electronic Set, in 1946. The set included a massive cast metal 671R Turbine (based on the Pennsylvania S2 Turbine locomotive) for motive power, tender with whistle, a boxcar, gondola, ore-dump car and caboose.
While the PRR built only one S2, Lionel built a lot of the model 671 locomotive. The "R" in the part number indicated Radio.
Each car could uncouple anywhere, with the press of a button. The set was a technical wonder, and a maintenance nightmare. Troublesome operations and a $75 price tag resulted in the system being discontinued in 1949. A big problem was dirty track and poor rail joints. To counter this, stainless steel was employed for track and axles. This was the second majour postwar innovation from Lionel, after the smoke unit introduced in 1945.
The set was withdrawn in 1949, due to high cost and poor sales. These sets do command a good price on the collector market, but are rarely seen in operation.
Read more about Lionel on Google Books
The transmitter was built around a 117N7GT vacuum tube that functions as an oscillator and a rectifier. Ten buttons controlled the operation of the oscillator, which produced RF signals from 230 to 350 kHz. This signal, measuring about 3 volts, was superimposed on the 60 Hz AC track power.
Each receiver is a series tuned circuit, with a rectifier and a relay. The receiver is tuned to a specific frequency, which activates whistles, couplers or a dumping mechanism. Two types of receivers were made. One type was for the locomotive, the other for rolling stock. The tender would have two receivers installed, one to operate the whistle motor, the other to control the reversing unit. The other type (of which there were four channels) operated the coupling mechanism, and in the case of the dump car, the dumping mechanism. To dump a load, the user simply held the button down for three to five seconds, which activated a thermal relay, which in turn controlled the unloading mechanism.
The channels were set up as 1/2 for the locomotives, 3 for the caboose, 4, boxcar, 5, gondola, 6/7 controlled the whistle motors, 8 was the dump car, with 9 and 10 being spares. The locomotives and caboose were fitted with RUB receivers, the boxcar was an RU, RUA for the gondola, RUD for the dump car, and the whistle was controlled by an RUC receiver.
The RUB and RUC were considered high frequency units, and the RU/RUA/RUD were low frequency units, channel 1 being the highest frequency. A complete RU-1 receiver was $5.00. Tuning was accomplished with a slug or plunger inserted in the input coil, which formed the primary of a transformer. A $2 tuning assembly completed the receiver.
The setup was like a command station/booster in two units. The transformer was connected to the Electronic Control Unit, and the ECU was then connected to the track. Lionel recommended feeders for long runs of track. The rolling stock was fitted with stainless steel axles to improve conductivity.
The vacuum tube used functioned both as an oscillator, and a rectifier. A 117N7GT is a tube with a 117 V filament (no filament transformer needed). It combined a diode and a pentode in the same package, the maximum voltage on the plate and screen was 117 V, and it was classed as a Class A Amplifier Half Wave Rectifier. Its power output was 1.2 W maximum. Lionel chose this device to simplify the design and keep the cost down.
Roundel Track Master
The Roundel Track Master appeared in an advertisement in the September 1962 issue of Model Railroader. It claimed to be able to control several locomotives. The Track Master II claimed to eliminate a lot of wiring issues such as reversing loops.
Outside of a few samples, the system seems to have never made it past the prototype stage and was never sold commercially.
A preproduction sample of the Track Master was reviewed by MR in March 1963, the receiver was quite large and appeared to be installed in a boxcar. A third unit, the Track Master III was mentioned as well. It would be noted in later issues that the system never went past the samples MR received for review.
Automatic Simultaneous Train Controls
The first command control system since the Lionel Electronic Control System. Designed and manufactured by General Electric.
See the main article on Automatic Simultaneous Train Controls for more information
A refined ten channel version of the discontinued ASTRAC system offered by GE, manufactured by Alphatronics.
Featured 10 channels, compatible with ASTRAC, and additional channels were available by special order. A basic two channel system cost about $300, and decoders were $40 to $50 (in 1979). Track voltage was about 19 V. Alphatronics began manufacturing a receiver compatible with ASTRAC in 1972, and announced a compatible transmitter in mid 1972.
It was described as a ten channel, AC carrier wave, frequency controlled system.
Alphatronics offered three configurations: A single fixed channel transmitter, a transmitter which allowed selection of any one channel using buttons, and a transmitter with a rotary switch to select one of ten channels. The transmitters could be ordered with tethered throttles. The throttles could be plugged in at remote stations. When the throttle was disconnected from the system, the train would stop. The throttles were simple units with a speed control and reversing switch.
Two receivers were offered. The A3 was a single unit about 3/8 x 1/2 x 1.5", and the A4, which was split in two parts for fitting into a tight space. The receivers were often installed in a dummy unit. The A3 had enough capacity to handle up to three locomotives in a consist. The decoders were three wire types. The A3 retailed for $35.75, while the A4 was $50.
The Digitrack 1600 offered 16 channels. Manufactured by Electro-Plex, allowed change of channel in locomotive by changing a plug. First mention was in 1972. A basic four channel starter set sold for $339.95. Additional channels cost extra. The system went out of production in 1975.
It was the first system to use digital control signals superimposed on a DC voltage (time division multiplexing), but the cost and complexity of the system doomed it.
The system worked by transmitting 16 pulses sequentially, one for each receiver. The pulse was nominally 250uS (microseconds), and could be as long as 500uS. Using timing, when the pulse began and ended in relation to a fixed point in time determined direction and speed. A sync pulse locked the timing of the receiver to that of the transmitter, allowing it to count pulses and determine the instruction intended for the receiver. The difference between the clock and the pulse determined speed and direction.
Instruction pulses were transmitted 100 times a second.
Model Railroader purchased the publication rights to the system and planned a series on constructing and operating a Digitrack system. Upon review, it was determined to be to expensive for a do it yourself project, and the Digitrack 1600 evolved into the CTC-16 system that appeared in the December 1979 issue of MR. Digitack is compatible with CTC-16, which used more advanced components that were available at the time.
Another device called "DigiTrack" was unrelated, as it was a handheld throttle. Kato also called their system Kato Digitrack.
This system appears to have been another planned but never truly realized product.
(Mehrzug Elecktronic 80 / Multi-train Electronic 80)
The ME-80 was made by A Fienwerktechnik in West Germany, and sold in the US by Janssen Enterprises.
An advertisement for the system appeared in the June 1976 issue of Model Railroader. It did not contain many details, but it did claim the ability to control up to six locomotives without the need for a block system, 'forwards, backwards, fast and slow' the ad stated. The front panel of the main unit pictured was labeled in German. It bore the appearance of a piece of high-tech electronic test equipment with it's aluminum face, blue cabinet and a wire stand which raised the front of the unit.
The main unit had six slide switches, which allowed the user to set the hand-held unit's channel. The front panel had the selector switches, indicator lamps, fuse holders and six DIN plugs for the hand-held interface. There were also the "Telex Crystal" (sound accessories), receiver crystals and rectifiers available to be installed in your motive power. Like many command control systems, it put constant power to the track and claimed to eliminate a lot of wiring.
The suggested price was $925 (in 1976).
See the main article, CTC-16.
A 16 channel system, superseded by the Railcommand system. Appeared in 1979. Model Railroader magazine published a series of CTC-16 articles as a do-it-yourself project. Based on the Digitrack 1600, with simpler construction using newer integrated circuits available at the time.
Another CTC-16 compatible system called CTC-16e appeared in 1984. Again, designed for people to build themselves.
The CTC-16e featured a dedicated throttle, or a selectable channel throttle which used what was called the T/BUS.
The dedicated throttle was built for a specific channel. The T/BUS throttle featured 16 channels, with a three wire connection to the system bus. T/BUS allowed channels 0 to F, which were digitally transmitted to the command station. The T/BUS throttle featured momentum, braking and throttle memory.
Another evolution of the CTC-16 concept, with 64 channels.
The DIGIPAC 316 was a commercial version of the CTC-16, manufactured by Mann-Made Products. It appeared in 1982, offering 16 channels. It claimed to work using Digital Proportional electronics, despite the fact it was an analog command control system based on the CTC-16 project published in Model Railroader.
Prices were as follows (for 1982): Power station, $61.50, control station 105.90, throttle with a knob was $19.95, or with pushbuttons, $17.85. The receivers were $39.50, channel selector plugs $5.95 each, and selector receptacles $4.95.
A selector receptacle was needed at every position you wanted a throttle to be plugged in. This was then wired to the control station. If you wanted to use all 16 channels, a 19 conductor wire would be needed. Wiring the receptacles was one of the most time consuming parts of the entire installation. The selector plug could be connected to any throttle and then plugged into a receptacle.
The system allowed "Plug Around" operation, which was their name for memory operation. The speed and direction would be maintained, but over time the train would slow to a stop if the throttle was not plugged in.
The receivers were designed to fit HO equipment without cutting. They were 11/16" wide, 4 9/16" long, and about 3/8" in height, for the diesel (D1) version, and were capable of 1A surge and half an amp continuous. For Steam, the S1 was 1 1/8 X 2 3/4 X 1/4", or the S2 at 1 1/2 X 2 3/8 X 1/2", and offered the same current capabilities as the D1. Mann-Made promised receivers for N scale.
W. Alan McClelland installed the DIGIPAC 316 system on his Virginian and Ohio railroad, previously he had employed GE's ASTRAC system beginning in 1963.
In 1984 the Dash II version was released, which allowed up to 32 channels. It was compatible via upgrade with the CTC-16, but not the CTC-16e cabs.
For a review of the DIGIPAC 316 see the September 1982 issue of Model Railroader. The same issue also features the DIGIPAK 316 being installed on a project layout. It is also mentioned in the November issue's article on the V&O.
Planned software announced by Custom Control Systems in 1981, which would allow the dispatcher to control the model railroad from a computer, compatible with the CTC-16. The system would include software and hardware, with a design manual. Originally intended for the Radio Shack/Tandy TRS-80 computer, software was planned to allow other computers to be used. As a minimum, the system could control routes, cab signals, trackside signals and hump yards.
It is not known if this software package made it past the announcement stage.
Computer Throttle Control 80.
A later, computer enhanced version of the CTC-16 was the CTC-80. It was the third generation of the Digitack 1600, and used a Z-80 microprocessor in place of the analog processor used in the CTC-16. Manufactured by Keeler Rail Specialities. It appeared in early 1988.
Required a personal (micro) computer to control the system. Compatible computers were the Apple II, the IBM PC, or the Radio Shack Model III, which interfaced to the CTC-80 via the serial port.
The system could operate in 16, 32, or 64 channel mode, for up to 64 locomotives under its control, and 16 throttles could be connected to the system. Channels 17 to 32 were reserved for computer throttles. The CTC80 receiver offered 64 channels, compared to the 16 of the CTC-16 receiver.
The command station was $400, a throttle $75, and receivers were $50. A power station control card was $30. The power station was only available as a kit, or the power station control card could be used to upgrade an existing CTC-16 system. The full setup was only required if there was no existing command control system on the layout, otherwise upgrading a CTC-16 system was possible with fewer components.
Power Systems Inc., introduced Dynatrol in 1978, now sold asClassic Dynatrol. Dynatrol is an 18 channel system (originally only 15 channels were offered), using a track voltage of 13.5VDC, and a frequency shift reversing system. It used audio tones to transmit commands. Additional channels were planned to control sound effects.
Dyntrol uses a supersonic carrier, with modulation of the duty cycle to transmit information to a pre-programmed receiver in the locomotive. Each throttle has its own oscillator and modulator, which are controlled by the throttle and brake controls. The carrier frequency is determined by a precision resistor installed in a small plug, called a channel plug. Reversing the locomotive is accomplished by phase shifting the carrier slightly. Receivers were available in various sizes that could fit N scale and larger locomotives. Multiple power supplies ($55 in 1979) and blocks were needed to reach the 15 locomotive capacity of the system.
Channels were selected using key plugs. Momentum and braking effects were also available.
The system has been on the market since 1978. Dynatrol and Onboard were among the most popular command control systems in use.
A basic direct or non-momentum cab cost about $65, and a full function cab was $75. Receivers cost from $50 to $60 each.
EMS was manufactured by Trix in Germany and sold by Walthers in North America. It used a 9.5 kHz carrier to control a locomotive with a decoder. It worked with an existing DC control system, allowing both DC (analog) and EMS equipped locos on the same track. A controller and decoder rated at 850 mA would have cost over $100 in 1979.
One locomotive was controlled by the power pack, the other by the EMS system, allowing the two to operate independently of each other. The EMS controller was a single knob for speed and direction. Additional parts made it possible to bridge gaps in the track work, enabling the EMS equipped locomotive to travel independent of the block boundaries.
A receiver was $35, and the EMS controller $75.
Onboard Locomotive Sound and Control
The Onboard Locomotive Sound and Control system, by Keller Engineering, offered 20 (originally ten) channels, with a constant 12VDC on the track. It used audio tones to control the locomotives. A base system was about $376 (1986). Wireless throttles were also available.
A typical starter set came with a 5A power supply, a 16 channel handheld controller, two 1A motor controllers and the manual. The handhelds generated both throttle and sound commands with crystal controlled oscillators. They used a keypad, with keys for the sound effects, throttle up and down. Bringing the locomotive to a stop and holding the throttle key would reverse the direction. The keys were colour coded, and each handheld could control two locomotives. Signals from the throttles were fed to a mixer, each mixer could support four channels generated by two handhelds.
The receivers were called throttles, and were installed in a locomotive or dummy unit.
The Onboard system claimed to eliminate the need for control panels and block wiring.
Onboard offered steam locomotive exhaust sounds, bell and whistle. For Diesels, it featured a variable engine RPM exhaust, bell and six chime air horn sounds, plus constant lighting. Another optional feature was directional lighting.
Another accessory was a signalling system, for use with lights or semaphores.
Motor controllers available in 500mA, 1, 2, and 4A versions, and also for garden railways. Built in memory, with pure DC out at full speed.
Steam Sound unit
- Optical exhaust sync (or magnetic for outdoor use), automatic 2 stroke air pump, adjustable 6 chime whistle, bell.
Diesel Sound unit
- Exhaust controlled by motor voltage. Selectable 6 chime air horn, bell. The synthesizer as Onboard called it was usually installed in a dummy, and powered by a rechargeable battery maintained by the track power.
- Up to 100mSec of delay, with controllable echo repetition.
All sound units featured a 1 W amplifier.
A radio adapter was also available, using a Futaba unit, which was directly usable in large locomotives.
You can use Onboard sound modules with DCC. See the Digitrax Knowledge Base for details. (Operating Keller SU1990 Sound Unit with Digitrax Decoders.)
Sometimes called the "ProTrac R/C 1".
Protrac was a system announced in 1979 by the Model Rectifier Corp. The Protrac R/C 1 System 7000 controlled two locomotives, only one decoder equipped. It was similar in concept to the EMS system. According to a review in Model Railroader (November 1979), it didn't appear to be radio based. The Protrac 7000 featured a dual control console, which looked a lot like an R/C unit for model airplanes.
The system works by using DC to control the first locomotive, and a receiver using "Carrier Control" was installed in the second locomotive.
A later, promised R/C 2 System 9000 promised eight channels, with radio control for wireless operation.
MRC quoted prices of about $100, and $150. (1979)
An eight channel digital signal system using a constant 12VDC on the track. Manufactured by Integrated Systems.
A single tethered cab that could control one locomotive sold for $14. A dual channel unit was $20. The locomotive would continue to run while its cab is unplugged. The throttle featured a single speed/direction knob, and a switch to enable momentum/braking effects. There was a brake trim control to allow adjustments for the characteristics of your locomotive.
Another part of the system is the throttle-transmitter unit. It was the power supply and signal generation system. Channels were selected by plugging a cab into one of the eight jacks on the unit. Additional power boosters were available to increase the power available. The 4 amp throttle-transmitter sold for $75, and the accessory 8A booster was $50. Receivers cost about $25 each. To allow for more flexibility, remote jack panels were offered for $11, as well as bulk cable to connect it to the system.
The Regulated speed Full wave Positionable Throttle was a nine channel system using a constant 12VAC track voltage, and high frequency signals to control the locomotive. Handheld throttles (Throttle Control Unit or TCU) were $25 for a single channel or $50 for three channels. The Engine Control Units sold for about $53 (1979). A basic system (a triple TCU and three ECUs) was about $200.
The early units only offered six channels. The channels were fixed. Future systems promised nine channels.
The system was built around model aircraft radio control components. The ECU consisted of a servo motor driving a gearbox, which in turn drove a potentiometer controlling a transistorized throttle. The ECU also rectified the 12VAC to Direct Current for the motor. It was noisy during speed changes due to the servo and gear train.
The throttles featured rocker switches to control speed and direction. The throttles could only send one command at a time. Dirty track could result in loss of control.
The Salota 5300 was a West German system imported into North America. It used a constant track voltage of 16-18VDC, and offered 5 channels. The Salota Power Deck/Control Transmitter featured 5 knobs that controlled the speed and direction of the 5 channels.
It was suited to any scale that used 12 V motors. The control system measured 9.25 by 9.25 by 3 inches. Receivers measured 40 x 25 x 17 mm.
The system was advertised for $300 (including 2 receivers), and receivers were $40 each in 1979.
Airfix Multiple Train Control System (MTC)
An analog system introduced in 1979 by Airfix. Could control up to 16 locomotives, with a maximum of 4 at a time. The presence of an IF can on the receiver indicates it is a tuned carrier control system.
Main unit consisted of a console with sixteen selector switches to select one of four channels. (A,B,C,D), and trays for the hand held throttles (up to 4 could be accommodated). Track was energized with 20VAC at all times. Receivers were sold labelled as one of four groups, and part of install involved adjusting the tuning to the desired channel (one of 4 in that group) by adjusting the tuning slug in the IF can.
Prices were UKP 85.00 for the main unit, with two handhelds and two receivers. Additional handhelds were UKP9.95 each and receivers were UKP4.95 each. (In US dollars the prices would be approximately $179, $21, and $11).
A simpler two controller was advertised but never sold in 1981. Very basic with only two handhelds, and no channel selection. Airfix entered receivership at the time, which effectively ended the product and any future versions.
More info and pictures: Airfix Railway System
Introduced in 1987 by Fleischmann.
Hornby Zero 1
A true digital system. Introduced by the UK manufacturer Hornby to the US in 1980, and Canada in 1981. It was a digital system based around a Texas Instruments TMS1000 microprocessor, a four bit microprocessor able to address and control up to 16 locomotives.
For more information, see the main article: Hornby Zero 1.
It was the most popular of all the command control systems in use by the mid 1980s. (Model Railroader reader surveys). Components can still be found for sale on the internet. Questions often appear on on-line forums asking about using a system someone got, or wondering if it is compatible with DCC.
Offered their Power Grid Systems command control system, which was compatible with the Zero 1 system, in 1996.
ZTC Controls in the UK still support the Zero 1 system and have made improvements to it.
ZTC also make DCC decoders that can be programmed to work with a Zero 1 system, and their controllers have a mode that enables control of a Zero 1 equipped locomotive.
One of the founders of ZTC was employed by Hornby as part of the Zero 1 development team.
ZIMO began offering a digital command control system ZIMO Digital (BGT-1, FP-2, FZE-2) in 1979, around the same time as Hornby's Zero 1. The majour difference was the ZIMO system could control 99 trains and offered 16 speed steps. (Zero 1 only offered 14). Development began in 1977, with the product coming to market in 1979.
Zimo would continue to innovate, with computer controls and CTC capabilities. Zimo began selling NMRA compliant DCC systems in 1994.
Also called Kato Digitrack
The Kato Digital system appeared in the late 1980s and was discontinued a few years later. It had up to 100 addresses available, a primitive sound function, and capability to control switches, either with a controller or a computer via RS232 (serial port).
Capable of controlling up to 16 locomotives out of 100, with eight under simultaneous control. Up to 256 turnouts or other accessories. A square wave of +/-18V was present on the track, with the digital signals being present for the first 2mS of an 11mS pulse.
The system was proprietary, and decoders would only fit an HO locomotive (due to their size).
Advertisements for a Command Control System by KATO appeared in late 1986. The recievers where shown beside a ruler, ranging from 20 to 90mm in length.
- 4-501 Main Controller $420
- 4-502 Subcontroller $160
- 4-503 Switch Controller $160
- 4-504 Power Supply $175
The subcontrollers plugged into the main controller, as did the switch controllers. A maximum of three subcontrollers was possible, giving control to eight trains at the same time.
Locomotive controllers ranged from $70 to $80. Switch controllers cost $70, and the sound module was $7.
KATO dropped the system in 1992.
Marklin Digital appeared on the market in 1984. This system was designed for use with Marklin's line of Alternating Current HO trains. Developed by Lenz for Marklin. Uses Motorola parts, hence the different mode and compatibility settings. It is the system that uses the Motorola format for sending commands. It is not compatible with DCC, but some manufacturers support the Motorola format in their command stations. The original format supported up to 80 addresses. Marklin and Arnold would market similar systems based on the Lenz design, Arnold would later exit the agreement due to patent/licence issues.
Two Marklin systems were sold: Digital~ for their AC products, and Digital= for Direct Current.
Marklin would also introduce another digital system developed by a third party for use with their DC product line.
Although Marklin Digital sold well in Europe, in North America it didn't fare as well.
The system was first demonstrated in 1979, going on sale in Europe in 1984 and in North America in 1986. (Marklin Website)
Digital system that appeared in 1982. Reintroduced in 1987 as "Selectrix". Very small decoders, but more expensive (single supplier) than DCC. Trix is now part of Marklin, and the brand is used to identify their Direct Current products.
Progressive Cab Control
Progressive Cab Control (PCC) is a concept that first appeared in 1949. It used multi-deck rotary switches to set routes, and power could be routed in a progressive manner by the dispatcher as the train moved along the track. The system would evolve, using relays and eventually computers to control and route power automatically using block detection to control the power routing.
A well known example using telephone switching equipment was built by MIT students at The Model Railroad Club on campus. Later it was upgraded to a computer controlled system implemented with relays. They also used a Digital Equipment Corp. PDP-11 to control their layout.
With the adoption of DCC, progressive cab control fell out of favour. Any DCC system can be purchased and installed for less money, and with a lot less complexity, than a progressive cab control system, which relies on costly rotary switches as its backbone. (Rotary switches with multiple decks that can handle the currents needed for Multiple Unit operations are very expensive, having been replaced by microprocessors and solid state devices). Later versions employed computers to handle power routing.
DCC's advantage was simplification of wiring, rendering schemes like progressive cab control obsolete. Operations were enhanced by the operator not having to worry about blocks when operating on a DCC layout.
Master Zone Layout Control was a concept proposed in the mid 1970s by pioneering model railroader Ed Ravenscroft. It is based on Progressive Cab Control.
Control was divided between the Master, or dispatcher, down to the Zone which then connected the cab to the track (Layout).
The entire concept was to simplify the wiring while making it easier to control the flow of power. Again, while simplifying the wiring, it added a number of devices, making it a costly proposal. Details about the system can be found in the February and April 1974 issues of Model Railroader. One feature was the placement of controls for switches would be near where the operator would be, while being close to the switches themselves.
The underlying theory behind PCC and MZL was to simplify the wiring, reducing the complexity of operating a train. Both systems still required care and intervention on behalf of the engineer, distracting him from the operations of the layout.
Many command control systems attempted to reduce wiring complexity. Modern DCC has reduced the wiring, making operations all about running the train, and not interacting with power routing and control. The operator does not have to worry about crossing block boundaries, nor does the yard switcher have to use a string of cars to couple to a cut in another block, occupied by an active train. You control the train, not the layout.
Other Command Control Systems
Other systems that were either on the market or planned in 1979 included ECM, from the UK.
Keller Digital appeared in 1993. An advertisement in the January 1994 issue of Model Railroader (incidentaly, it's 60th anniversary issue) described the new Keller Digital system based on the proposed NMRA Digital Command Control standard described in the October 1993 issue of Model Railroader.
Keller Engineering described the system as having 125 channels, conforming to the proposed NMRA standard, each engineer could control a train with four different channels for locomotives. They also offered sound, walk-around throttles, and the capacity to handle up to 32 throttles (and engineers).
No computer needed, but one could be used to control the system. Short circuit protection, with up to 10A capacity. It also offered full compatibility with the Keller ONBOARD system, which could share the track at the same time.
Keller Digital featured a microprocessor based system, and was claimed to be adaptable to any modifications to the proposed NMRA Digital Command Control standard via software update.
A starter system was offered at the introductory price of $495, consisting of a heavy duty transformer, power supply, command station, keypad (throttle) and two decoders. Existing ONBOARD system owners could upgrade for $350 by using some existing components.
Developed the Marklin digital system (under contract). Lenz digital technologies are not compatible with DCC, except those products marketed as NMRA DCC Compliant.
Command Control in the 1980s
The March 1984 issue of Model Railroader had an editorial about Command Control systems.
Their 1983 annual reader survey revealed that about 10% of the respondent's layouts had some form of Command Control system.
The systems in use were found to be:
- Zero 1: 24%
- Onboard: 22%
- Dynatrol: 18%
- CTC-16: 11%
- Other: 25%
As shown, no one system was a clear leader. The largest installed base was Hornby Zero 1, a digital system, the balance were analog command control systems. None were compatible with each other either. The other 90% of model railroaders were using analog (direct current) control with blocks.
The Digital Command Control Advantage
Reviewing the various command control systems listed here shows why the NMRA’s Digital Command Control has succeeded. No two command control systems were compatible with each other. They were all unique, and being mainly analog based, compatibility was not really possible. The digital systems were costly and vendor specific. Many, if not all the command control systems on the market, were proprietary systems, manufactured and supported by a single company. When that company went out of business, their product line died with them. Or as demonstrated by ASTRAC, when General Electric lost interest, they halted further development and cancelled the entire ASTRAC product line. Hornby experienced financial problems shortly after the release of their Zero 1 system, delaying new products and effectively killing future development of the Zero 1 product line.
That command control systems were expensive and completely incompatible only further hampered their adoption. A fragmented market with expensive products prevented one command control system from becoming dominant, in addition to the lack of large players which could supply and support their products over the long term. In turn, that slowed adoption as many modellers chose to forego command control mainly because of cost and compatibility issues. The model railroad market was hesitant to invest in any expensive command control systems with the ever present threat of discontinuation.
Another key factor was future expandability, or lack thereof. Most command control systems were limited by the current analog technology, while digital systems, with expensive components like microprocessors, were limited by the cost of the technology available to them at the time. Those circumstances limited features such as the channels available to the user, unlike DCC, which can offer almost 10,000 unique addresses to the user. Today’s DCC has benefited greatly from the availability of a wide assortment of low cost components. Multiple suppliers offering products compatible with the NMRA DCC standards allowed for expandability and enhancements never considered possible prior to DCC.
Prior to the introduction of the Digital Command Control standard, the NMRA established a committee to study the command control marketplace, and create a unifying standard for command control systems. Quickly it was determined that a digital system was the best choice. The DCC Committee requested manufacturer submissions so they could examine possible technologies. Some chose not to participate, not wanting to jeopardize sales of their existing product line. Two companies submitted proposals to the DCC Working group, Marklin and Keller Engineering.
During the drafting process, the NMRA committee looked at various alternatives, including existing approaches and completely new designs. The signalling techniques used by a system designed by Lenz Elektronik exceeded requirements and employed a communication protocol offering the greatest future potential. While the signalling techniques are built around those of Lenz's design, numerous improvements by the NMRA committee created a packet format richer in features and unrelated to Lenz's command control technologies.
The NMRA does not endorse commercial products as standards, so Digital Command Control is purely an NMRA technology. This eliminated the need for a manufacturer who wishes to make a standards compliant product to first seek a licence from another manufacturer. The NMRA has a letter from Lenz confirming there was nothing in the draft Standards and Recommended Practices that may infringe upon any Lenz copyrighted, patented or proprietary information. The NMRA committee did make significant extensions to the original Lenz concept. In short, the standard is not based upon proprietary equipment, technology or system. It has its roots in the Lenz system, which has been made public.
(Information on the origins of DCC from the old DCC FAQ 1.9)
Material in this article was taken in part from a review of command control systems published in the November 1979 issue of Model Railroader, "Commercial Command Control Systems", Page 80 written by Andy Sperandeo. A footnote indicated that the December 1979 issue would feature the beginning of a series of articles on the CTC-16.
Hornby pricing: Hornby advertisement, March 1981, Model Railroader.
As one can see by the pricing shown, command control systems were quite expensive in 1979, slowing their adoption. DCC, on the other hand, is a lot cheaper, or comparably priced with respect to the analog systems of 30 years ago.
For comparison of prices in today's dollars, you can try the Inflation Calculator. For example, the $9.95 MSRP (in 1963) of an ASTRAC receiver would be equal to about $74 in 2011. Or the $64.95 GE asked for the transmitter: $480 in 2011.
The NMRA DCC standard is not based on the Lenz system, and contains no Lenz technologies or patents.