+avoid retransmitting too often (S9.2 C l114-)
+
+as a result of running, then touching track near panel to induce detection
+
+
layout polarity diagram colourful segment encoding:
- implement segmap so that we can do midx
- decide what to do about crossings (difficult to show both tracks)
- wire layout diagram thing into Tcl and see speed etc.
make moveable feature selection in subseg2display bitwise rather than
setwise
-1. Write lots and lots and lots of PIC programs
+safety system no crashes at crossovers please