PLC programs can use timers as well as __________ to sequence events.

In PLC programming, timers are commonly used to manage the timing of operations, but they can also interact with additional components to create effective event sequencing. Limit switches play a crucial role in this context as they are often utilized to signal when a specific condition has been met within a system, enabling the PLC to proceed with executing the next steps in a sequence.

Limit switches act as physical inputs that detect the position of a machine part or the state of a process. When a limit switch is activated, it provides the PLC with real-time feedback about the system's status, allowing for precise control and sequencing of operations based on that feedback. This integration is essential in applications where the timing of events must correspond closely with physical actions, such as in automated machinery or conveyor systems.

The other options, while relevant to PLC functionality, do not directly complement timers in the same context. Inputs generally refer to signals received by the PLC from various sensors, while outputs are the actions taken by the PLC, such as activating motors or lights. Registers, on the other hand, store data and are more relevant to data processing rather than event sequencing in conjunction with timers. Hence, the collaboration between timers and limit switches provides a robust mechanism for effective event sequencing in PLC programs.