__________ sequencing uses timer relays in place of limit switches to sequence the operation of a machine.

• A. Time-driven
• B. Event-driven
• C. Manual-driven
• D. Pulse-driven

Answer: (A)

Time-driven sequencing uses timer relays to advance the machine through its steps after fixed time intervals, instead of waiting for a limit switch or sensor event. In this approach, each stage runs for a preset duration defined by the timer, and when the timer finishes, it triggers the next stage in the sequence. This makes the overall operation run like a clocked routine with predictable, repeatable timing.

This differs from event-driven sequencing, which advances based on external signals from sensors or limit switches; manual-driven sequencing relies on operator input to move to the next step; and pulse-driven sequencing progresses in response to discrete pulses from a counter or pulse source. The characteristic feature here is using timers to control the timing of each step, not reactions to events, manual actions, or pulse counts.