What is the key difference between an Anti-two-block warning device and an Anti-two-block prevention system?

The key difference between an Anti-two-block warning device and an Anti-two-block prevention system lies in their functional capacities. The warning device serves to alert the operator when the load hook is nearing the limit of the boom tip, thereby providing a visual or audible warning that a potential two-block condition is about to occur. This type of device is crucial for informing the operator to take corrective action and prevent damage.

In contrast, the prevention system goes a step further by automatically stopping the crane's operation before a two-block condition can happen. This means the prevention system is more proactive in ensuring safety by eliminating the possibility of collision or entanglement between the hook and boom. The ability to stop operation allows operators to avoid an incident altogether, promoting a higher standard of safety in crane operation.

The other options do not accurately capture the core operational differences between the two systems. The warning device's primary role is to provide alerts, while the prevention system actively intervenes, making option B the most relevant and accurate choice regarding their functions.