FAQ:My Train Keeps Stopping

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DCC Categories Beginner, Throttle
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If a train, that for no obvious reason, suddenly comes to a stop and adjusting the throttle causes it to resume its journey, the likely cause is two throttles are sharing the same address.

Some DCC systems allow two throttles to control a single address for the purpose of operator training, creating consists, and other functions. Digitrax uses the term Steal to indicate that the address is currently in use, and the operator can choose to take (steal) control of the address or not.

The second throttle is often referred to as a Ghost or Phantom Throttle. A product of poor operator discipline, as someone hasn't cleared that address from their throttle during a previous operating session, or earlier in the current session. That throttle is set to a zero or non-zero speed, and will regularly be polled by the command station. When that happens the ghost throttle overrides the throttle in use.

Digitrax DCC Systems:

  • Every throttle, which is a LocoNet device, creates a slot when it selects a locomotive's address. The slot associates the throttle with that address.
  • Variables such as speed, direction and active functions are written to that slot by the throttle. This allows the throttle to be disconnected from LocoNet without impacting the operation of a train.
    • This also allows a throttle to control multiple trains independently using multiple slots. Another throttle can steal an address, which creates a new slot associated with the second throttle.
  • There are two slots assigned to that locomotive's address. One slot is set to speed zero. At some point the command station will refresh the slots. It reads the slot which is set to zero speed and sends a packet addressed to your locomotive telling it the speed is zero…

JMRI can help by using the slot monitor to clear all unused slots, or to release a specific slot.

See the article about dispatching for more details.