Roco and Fleischmann Z21 Manuel D'utilisation page 47

The same signal can be set in a similar manner in TrainController.
However, if a signal recognises more than 8 aspects, then two commands are required:
First a switching command is sent, using which a certain group of up to four signal aspects is preselected ("Mode").
Then a second switching command is sent, with which one of the four signal aspects mentioned is selected and displayed ("Trigger").
The Z21 signal DECODER uses the first two turnout numbers (1R, 2R, 1G, 2G) as trigger, and the last two turnout numbers (3R, 4R, 3G,
4G) for the mode. In this way, up to 4*4=16 different signal aspects can be switched.
It is clear that such complex signals are less suitable for manual operation, and better for use in set routes and PC control programs.
Example: SNCF main signal (Signal-ID 240 "SNCF Carré C [CFH]") in iTrain.
Z21 ist eine Innovation von FLEISCHMANN und ROCO
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