Automatic Tool Changer
From PROBOTIX :: wiki
http://linuxcnc.org/docs/html/remap/remap.html#_the_remap_statement
http://linuxcnc.org/docs/html/remap/remap.html#remap:how-tool-change-currently-works
https://forum.linuxcnc.org/10-advanced-configuration/31754-how-to-build-atc-carousel-in-linuxcnc
https://forum.linuxcnc.org/10-advanced-configuration/30123-m6-remap-problem