Which type of elevator control does not switch until all calls in one direction are answered?

The concept of selective collective control in elevator systems is designed to optimize the efficiency of elevator operations. This type of control allows the elevator to respond to multiple calls in one direction and will not switch its direction until all calls in that specified direction have been satisfied. This minimization of unnecessary stops ensures that passengers experience fewer delays, as the elevator can effectively gather and serve calls made in the same direction before changing course.

Selective collective control is particularly valuable in buildings with high traffic, as it can reduce travel time and improve service speed. The system balances responding to each call with the need to minimize travel distance and time, making it a preferred choice for many modern elevator systems.

In contrast, other options like simple control and collective control operate on different principles that do not inherently prioritize the completion of all requests in one direction before switching. Dispatch control, while focused on optimizing service, generally employs a different algorithm for managing call assignments that may not align with the concept of responding to all calls in one direction before switching.