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Mixing Booster Brands

In this section, we are talking about how one can interface different brands of command stations with different brands of standard boosters.

QUICK RECOMMENDATION:  ALTHOUGH THIS IS POSSIBLE, THIS IS NOT RECOMMENDED FOR THOSE WHO ARE TECHNICALLY CHALLENGED.  DO NOT MIX BOOSTERS.   ONLY BUY THE SAME BRAND AS THE COMMAND STATION.  THERE IS NOTHING "PLUG AND PLAY" HERE.

The NMRA DCC standards released back in 1995/6 intentionally never defined the signal levels and the connections between command stations and boosters because the goal of the DCC standards was focused at the track level.   The result was a wild west of connection systems.   Dispite that, the one thing that was common was the basic need to have at least one pair of wires that contains the DCC signals that carried the DCC command information for the booster to send to the track.  This made interchangeability a possibility. 


1) INTERCHANGEABILITY = CUSTOM CABLES
There are several technical problems that present challenges to the mixed system user.  They are:

a) DIFFERENT CONNECTORS: Most DCC brands used different connectors to establish the connection between the command station and the boosters.

b) DIFFERENT SIGNAL PINS:  Even if the connectors were the same, there was no interchange ability at the pin level.  Booster signals would be sent down different pins numbers on different systems.

The above problem of different connectors and signals mismatched by pin numbers can be addresses with the use of a custom built adapter cable.   Some DCC system provide information on how to build these cables and some do not.  


2) BOOSTER LOAD PROBLEM
Even if you can figure out the adapter cable design, there remains one less obvious but important technical problem.  The ability of the command station to have enough power to drive the "out of brand" boosters.   In other words, each booster's input places a load on the command station booster output signal.  If the command station does not have enough power to drive all of the boosters connected, the boosters will not work reliably and consistently.  

In July 2003, DCC Standard S 9.1.2 was released defining the electrical characteristics of the signals that go between the command station and the boosters.  This standard was not about solving the connector and pin problem.  However to date this DCC standard has not been much help because:

a) it came to late.  All of the name brand DCC systems had already defined their own proprietary command station to booster connection system and it works.  It's only chance of success would have been if it was introduced with the original set of DCC standards.

b) there is no financial gain motive to support it.   Supporting this standard meant that the given DCC manufacture could be loosing booster sales  to competitors.  DCC manufacture all want to lock you in to their brand to keep you as a loyal long term customer.

c) it did not define a single universal interface.  It simply took the two most popular custom booster interfaces and defined a common conformance load condition for both interfaces to meet.  However the voltage levels and current levels of each booster interface using the conformance load are not 100% compatible with each other at upper and lower extremes.   The two booster interfaces chosen are:

1) NCE (Current Interface).
2) Digitrax (Voltage Interface).

At best, the standard has helped us understand what it takes to mix NCE and Digitrax equipment.


3) COMPATIBLE ELECTRICAL WORKING RANGE (NCE and Digitrax)

The following is a summary of the NMRA S-9.1.2 standard specifications with a 1K load.

InterfaceDevice
Signal
Type
Max
Current
Voltage
Range
Voltage
Reject
NCE
Current
Cmd Station
Unipolar
or bipolar
differential
1000mA
8V-22V
N/A
NCE
Current
Booster
Unipolar
or bipolar
differential
25mA
@ 10V
7V-22V
<4V
Digitrax
Voltage
Cmd Station
Unipolar
or bipolar
differential
100ma
3V-12V
N/A
Digitrax
Voltage
Booster
Unipolar
or bipolar
differential
2.5mA
@ 5V
2.5V-12V
<2V

COMMON COMPATIBLE WORKING RANGE:  Unipolar or Bi-polar differential within a 4V to 12V voltage range without exceeding more than a total of 100mA booster load draw from command station.  If one can keeps the voltage and currents within this range, then the two systems can freely interchange command stations and boosters with adapter cables.

To learn more about interfacing a NCE command station to Digitrax Boosters, go here: Mixing NCE & Digitrax