The compensating sheave switch must open before the sheave reaches which limit of travel?

The compensating sheave switch is a crucial safety device in elevator systems, designed to help prevent malfunctions or potential accidents by monitoring the position of the compensating sheave. The switch must open before the sheave reaches either the upper or lower limit of travel to ensure that the elevator operates within safe parameters.

When the compensating sheave switch opens before the sheave reaches these limits, it allows for an early warning mechanism, enabling appropriate actions to be taken to prevent the elevator from exceeding its safe operational range. This precaution helps to maintain system integrity and protect both the passengers and the equipment from damage.

Travel limits typically refer to the restrictions on how far the elevator can safely operate. By establishing that the switch must open prior to hitting these boundary limits, the system can effectively prevent scenarios that could lead to breakdown or hazardous conditions during operation. In contrast, the other options lack the precise terminology that accurately captures the operational context and safety requirements of the compensating sheave switch in an elevator system.