Thank you -- this suggestion works, but ...
- I have 190 stations and did not want to re-wire them of all (just the ~15 pollution filter stations).
- The default setup was so nice, that I had previously removed all circuit connections to my train stops.
- The short circuit global requires a ...

There are global settings which determine if trains should finish unloading at the requester station, and I like this option for most stations.
However; for other stations (like the pollution filters for K2+SE), I want to have an inactivity timeout and only load the amount requested.
It appears ...