49 CFR § 236.11
Adjustment, repair, or replacement of component
November 18, 2020
When any component of a signal system, the proper functioning of which is essential to the safety of train operation, fails to perform its intended signaling function or is not in correspondence with known operating conditions, the cause shall be determined and the faulty component adjusted, repaired or replaced without undue delay.
[49 FR 3382, Jan. 26, 1984]