Book excerpt: Programmable Controllers is an introductory PLC text introducing the operation, programming and interfacing of the Allen-Bradley Pico 1760 PLC. The text builds from a foundation of electromagnetic relays with associated ladder diagrams and progresses into general purpose PLC internal operations, 1760 operational specifications, I/O considerations and common PLC applications. PicoSoft ver 6.22 is introduced with sample laboratory experiments and chapter problems applying the software to solve realistic application examples. A basic understanding of component-level electrical, electronic and logic switching concepts is beneficial but not required to use this book.