The DB150 has 22 “Slots” for locomotive addresses The DB150 command station can run up to 22 loco addresses and throttles at a time.
Each of these addresses occupies one of 22 “slots” available in the DB150’s memory.
Once those 22 slots are full the system will display the “slot=max” message to let you knot that you need to release some locos if you want to select and run others.
The DB150 manages the addresses that occupy slots by assigning different statuses to each decoder depending on how it is being used in the system.
This allows the DB150 to automatically remove, or purge, addresses to make room for other locos to be selected and run.
There are two factors that determine the status of each decoder: whether or not it is selectable and whether or not the command station is refreshing it.
Decoder addresses are selectable if they are not being used by any throttle in the system.
When your command station is running a loco on an address, it sends commands and refreshes those commands.
The 22 address limit is the number of addresses that your DB150 can refresh at the same time.
When the command station refreshes data sent to decoders, it is just repeating previously issued commands.
The reason for this is to be sure that the decoders don’t forget what they are supposed to be doing.
For example, if your decoder encounters a power interruption caused by dirty track, it is momentarily out of contact with the command station and it might lose the DCC signal.
By refreshing the decoder’s data, the command station makes sure everything keeps running smoothly.
Your Digitrax system classifies decoders as follows:
Purging of addresses:
Purging is the process by which the DB150 changes the status of decoders that are either not being used or are unattended to make room for other addresses to be selected and refreshed by the command station.
If a DT40x series throttle with selected in-use locomotives is unplugged from LocoNet for more than about 200 seconds, the command station will change the status of these in-use locomotives to common so that they are available for selection by other throttles in the system.
When this happens you will hear three beeps from the DB150.
When the DT40x series throttle that has been purged is plugged in again, it will attempt to log on to the system where it left off.
If the addresses that were previously in-use on the throttle have not been selected by other throttles, the wayward DT40x series throttle will automatically re-log on to the purged locomotives and their status will be changed back to in-use.
If the throttle is a radio or IR throttle, this will not happen as long as there is an active LocoNet link.
In the case of both tethered and tetherless operation with IR and Radio throttles, the throttles periodically send a message to the system to keep them logged in to the system so that their locos selected are not purged.