Define 'hold-open' time and its safety considerations.

• A. The time the gate remains open after activation; adjustable within safe limits to avoid entrapment and ensure entry.
• B. The delay before the gate starts moving.
• C. The duration of safety devices self-check.
• D. The maximum travel length of the gate.

Answer: (C)

Hold-open time is the period after the gate has finished opening that the gate remains in the fully open position before it starts to close again. This dwell is adjustable within safe limits to allow enough time for people or vehicles to pass, while avoiding leaving the opening open longer than necessary, which could pose safety or security concerns.

Safety considerations include setting the duration to match actual traffic flow, ensuring there are reliable detection devices (like sensors or safety edges) so the gate will stop or reverse if someone or something is in the opening, and guaranteeing that the hold-open timer does not defeat safety interlocks or cause entrapment. If a person or object is detected, the gate should not close; the system should re-check for clearance and, if appropriate, reopen. The hold-open time should be chosen to balance efficient access with the risk of leaving the opening exposed to weather, interference, or misuse.

This concept is not about the delay before movement, the self-check duration of safety devices, or the maximum physical travel length. Those are separate timing or specification aspects of the gate system.