Mark was kind enough to send me the product list. He also installed a safety switch in case the proximity switch failed but I'm not sure where he sourced that from. Hopefully Mark can answer how everything was put together.
The proximity sensor - INDUC PROX 18mm SHIELDED PNP 8mm RNG 4-WIRE 10-30VDC N.O./N.C. 4-PIN M12 Q/D
Proximity sensor cable - CABLE M12 2m (6.5ft) Q/D 4-POLE RT-ANG FEMALE BLK PUR
I also have two-stage braking: 1 sec. is used for 900 rpm and below, 3 sec (maybe 4?) for above that. It takes a WHOLE bunch of energy to stop a 80 lb. chuck spinning at 2000+ rpm...
Mark's control systems are superb . He makes a simple lathe into a "Smart Lathe". I grin ear to ear now when operating my Smart lathe.