What is the purpose of the PKO (Power Knock Out) by-pass?

The purpose of the PKO (Power Knock Out) by-pass is to provide a false brake release light. This functionality is essential in specific operational situations where it might be necessary for operators to have a visual indicator that suggests the brakes on the train have been released, even when they may not have been. This can facilitate certain operations or troubleshooting processes, especially in instances where the braking system needs to be tested or adjusted without actual release, which helps in maintaining safety protocols.

While the other options may relate to different aspects of train operation or safety, they do not capture the specific role of the PKO by-pass in providing this visual brake status indication. For instance, enhancing train speed involves factors related to throttle control and engine performance rather than brake indicators, and maintaining air pressure levels pertains more to the functioning of the air brakes themselves rather than the visual feedback mechanism provided by the PKO by-pass. Similarly, while coupling procedures are critical, they involve physical connections between train units rather than the operational status indicated by brake lights.