In industrial automation, a drum timer is best categorized as which type of control element?

Introduction / Context:
Legacy and modern machines often execute a fixed series of operations. Drum timers are classical devices used to coordinate timed steps in a predefined order, making them a canonical example of sequence control.

Given Data / Assumptions:

• The device is a 'drum timer'—a rotating drum with cams or notches actuating switches in time.
• Goal: identify its functional category.

Concept / Approach:
Sequence controllers step through operations based on time or position cues, energizing outputs in a particular order. A drum timer is precisely such a device: as the drum turns, switches open/close to trigger successive actions, e.g., in washing machines or assembly lines.

Step-by-Step Solution:

Verification / Alternative check:
Historical control schematics show drum timers as the heart of step-based automation prior to PLCs.

Why Other Options Are Wrong:

• Input sensor/position sensor: drum timers do not measure a process variable.
• Output actuator: while they energize outputs, the defining function is sequencing, not actuation energy conversion.

Common Pitfalls:
Confusing signal sequencing with actuation; actuators convert energy (e.g., motors, valves), while drum timers schedule signals.

Final Answer:
a sequence controller