Controller types, I/O types, function block vs. line programming, selection criteria, power and wiring fundamentals, and why stand-alone control logic belongs in the controller rather than at the supervisory level.
Direct digital control (DDC) panels are the hardware that actually closes the loop between a field sensor and a field actuator — the reflex arc Module 1 introduced by analogy and Module 2 placed architecturally. This module goes deep on the hardware itself: unitary/terminal controllers versus application-specific versus general-purpose programmable controllers, the analog, binary, and pulse I/O types every points list is built from, and how function block and line programming actually differ in practice.
By the end of this module you should be able to select an appropriately matched controller for a given application, wire it correctly with proper shielding and power sizing, and explain why pushing safety-critical or core control logic up to the supervisory level for programming convenience reintroduces exactly the single point of failure the distributed DDC architecture exists to avoid.