Which type of fire alarm system connects to the building's existing fire alarm system without needing its own power supply?

The secondary or auxiliary fire alarm system is designed to connect to an existing primary fire alarm system without the need for its own separate power supply. This system typically uses the infrastructure of the primary system, allowing it to rely on the main system’s power for operation. This can simplify installations and reduce costs, as it eliminates the need for additional power sources.

In contrast, a primary fire alarm system refers to the main system that initiates alarms and alerts. A wireless fire alarm system functions independently over radio frequencies and requires its own power supply source, which is contrary to the question's criteria. A networked fire alarm system involves multiple interconnected alarm systems that communicate with each other and possibly share a centralized power supply but does not fit the specific definition of an auxiliary system. Hence, the classification of the secondary or auxiliary fire alarm system accurately fits the requirement described in the question.