On 3/6/2025 10:31 PM, Marc N Fournier via groups.io wrote:
First off, no DCC System will READ on the Main without additional hardware.
Not quite.
I own a commercially-available DCC command station which _can_ read mobile decoder CV values "On the Main" from _some_ mobile decoders _without_ additional hardware. Owned it for a few years. There are some other DCC command stations, by different manufacturers, which can do so, too.
But _all_ of these systems have limitations for allowing "Programming on the Main CV Reads", including:
. Those command stations can support "reading of mobile decoder CVs On the Main" from only certain types of mobile decoders. Some of these solutions only support reading of mobile decoder CVs On The Main when using the DCC system manufacturer's decoders using its special electrical signaling. Other solutions support a different electrical mechanism that is aligned with the NMRA's optional "RailCom" feature. If the mobile decoder does not support the required electrical signaling solution, then the decoder cannot be "read" using the command station's special hardware which can otherwise support CV Reads when performing "programming on the Main".
- Those command stations can support "reading of mobile decoder CVs On the Main" when the supported decoder decoder is on a chunk of track that is powered by the command station's DCC Track outputs. If the mobile decoder is located on track powered by a different "booster", it will (probably) not be readable "on the main".
- Those command stations can support "reading of mobile decoder CVs On the Main" when the supported decoder decoder is configured to allow Programming on the Main "Read" access. If the decoder supports the Programming on the main Read" feature, but has it "disabled", then the mobile decoder will not be able to perform "programming on the main reads".
Other restrictions may apply, like "certain manufacturers' decoders put so much electrical interference onto the DCC track signal that they can prevent Programming on the Main CV Reads from working reliably to _other_ decoders". In this case, it may be necessary to remove those badly-behaving locos from the command station's trackage when trying to perform Programming on the Main CV Reads.
FYI - I believe that at least _some_ Tsunami mobile decoders _can_ have their CVs "read" via "Programming on the main" with a certain manufacturer's command station hardware. Check with SoundTraxx and the command station's manufacturer for confirmation.
