Relay ladder logic and ladder logic for a PLC program are similar because the output symbols and control logic are on a rung, but different because the PLC ladder never has field device switch contacts located in it.

Question

Quizplus · Accepted Answer

In PLC ladder logic, the control logic is represented by symbols on a rung, similar to relay ladder logic. However, PLC ladder logic does not include physical field device switch contacts; instead, it uses software representations of these contacts.

Relay Ladder Logic and Ladder Logic for a PLC Program