What indicates that bridge equipment is connected to casualty power?

The indication that bridge equipment is connected to casualty power primarily relies on the presence of CAS PWR terminals. These terminals are specifically designed for connecting power sources in situations where standard electrical systems are not operational, such as during casualty scenarios. By using these terminals, personnel can easily identify that the equipment is receiving power from a backup or emergency source, which is critical for maintaining operational capabilities.

While light indicators and alarm systems can provide feedback on system status, they are not unique to casualty power connections and may indicate other operational statuses. Color-coded cables are useful for organization and safety but do not specifically denote a connection to casualty power. Therefore, the CAS PWR terminals serve as the direct and clear indicator of the connection, making this choice the most accurate in the context of the question.