When the anti-two-block (A2B) lock-out device is activated on a telescopic crane, which functions should be disabled?

When the anti-two-block (A2B) lock-out device is activated on a telescopic crane, it is crucial to ensure that specific crane functions are disabled to prevent damage to the crane and to maintain safety. The correct choice indicates that, with the A2B lock-out engaged, the crane should disable the ability to hoist up, extend out, and lower the boom.

The rationale behind this is rooted in the purpose of the A2B device, which is designed to prevent the hook block from coming into contact with the boom tip. This contact can cause severe damage to both the crane and the load, potentially leading to dangerous situations such as crane failure or accidents involving workers or nearby structures. By disabling these functions, the A2B lock-out ensures that the crane operator cannot inadvertently operate the crane in a way that could lead to two-block conditions.

In contrast, other options that suggest disabling only one or two of these functions do not provide adequate protection against the risk posed by two-blocking. The preventive measures offered by the A2B lock-out device necessitate a comprehensive halt to operations that could lead to such incidents, reinforcing the need for full compliance when the device is activated.