FAQ:What does 'Slot=Max' mean on Digitrax?

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The Slot=Max message means that you have used all of the available slots in your command station. Or you have the maximum number of locomotives allowed by your system in use.

On a DT400 or DT300, the display will show Slot=Max. Older DT100 or DT200 throttles will display FF, and the Zephyr shows FULL. All these indications mean that the number of slots available is zero, as all are in use.

For more information on the Slots and the Slot Max error, see the Slots article.

The maximum number of locomotives that can be run at any one time depends on the number of available slots in the command station. Each command station has a different maximum number of slots available. The DCS50 (Zephyr) has 10 slots, the DB150 (Empire Builder) has 22 slots, and the DCS100 (Super Chief) has up to 120 slots.

The number of slots used depends on a few factors including the number of locomotives in use on the system, the number of consists defined, and the consisting type used. For more information see the sections on consisting elsewhere in the DCCWiki.

If you receive a slots=max message you must free some slots on the command station.


It is a common misunderstanding that locomotives are associated with throttles, and that the limit on locomotives depends on the throttle. The number of slots available in the command station dictates the maximum number of locomotives that can be "managed" by the system at any one time.