A white paper from Electro Cam (Roscoe, IL) titled "Internal High-Speed Logic" explains in plain language what a programmable limit switch is and how it performs machine logic by using inputs from sensors and switches to trigger outputs such as solenoids.
Orion® PC-based motion controllers from Ormec (Rochester, NY) now offer Ethernet connections to Allen-Bradley PLCs that support Ethernet. The controllers can also be used for communications with PCs running popular human-machine interface software packages.
REB's (Menomonie, WI) PLC-controlled IVS system uses air purge and vacuum to clean containers before filling with aqueous or viscous product. It handles volumes from less than 1 oz to 1 L with accuracies of ±0.5% of the fill weight.