In Canada, fully signaled lines use CTC, where signal indication is the authority for movement. This system is supervised by a Rail Traffic Controller (RTC) who is in constant communication with the trains and engines on his territory. The RTC has the ability to line routes and give permissive signal requests to the system in the field from a central location. The RTC can also issue special permissions to trains via radio. In order to pass signals set at stop (Rule 564), reverse direction within a block (Rule 577) or enter the main line at a manual switch not equipped with a signal (Rule 568), the train crew must copy the RTC's instructions and repeat them back correctly before being allowed to proceed.