PLC and PAC systems are industrial controllers used to execute deterministic logic, motion sequences, and process coordination across machines and lines. Architecturally, they combine a CPU, power supply, chassis or backplane, I/O modules, and field communications that connect sensors, actuators, drives, and HMIs. Typical technical characteristics include scan-cycle execution, rugged operating ratings, onboard diagnostics, non-volatile memory, modular expansion, and support for industrial Ethernet and serial protocols. Functional capability includes discrete control, interlocking, sequencing, PID where applicable, recipe handling, alarms, and integration to supervisory systems. For operator visualization and panel computing, see HMI & Industrial Computing, and for network infrastructure and protocol connectivity, see Communication & Networking.
