Final answer:
During non-revenue hours, the main station gate is locked. FD units can access the gate using alternative methods such as a key card or a keypad code.
Step-by-step explanation:
During non-revenue hours, the main station gate is locked. In the case that the key is not available, FD units can access the gate using an alternative method such as a key card or a keypad code. These alternative methods provide secure access to authorized personnel even when the key is not present.