What would be a good option for a PLC rack used only for the purpose of training individuals on PLC basics? Preferably one with AI/AO/DI/DO cards and freeware to program field devices.
Automation Direct is a web based vendor of PLCs and associated components and controls.
They publish a 93 page text called Automation 101: Control System Engineering, A Condensed Guide to Automation Control, System Specification, Design and Installation
It's a free download. I suspect you have to register, but no salesman calls. Not bad for a freebie.
Their documentation is quite good, a rare compliment from me.