In a thermocouple fire detection system, pressing the test switch causes which component to close?

• A. The sensitive relay.
• B. The slave relay.
• C. The alarm bell.
• D. The master switch.

Answer: (A)

The test switch is wired to energize the sensing path so that the sensitive relay pulls in. Its contact is normally open and closes when the relay is energized, which completes the alarm circuit. So pressing the test switch causes the sensitive relay to close, initiating the alarm sequence. The slave relay, alarm device, and master switch are part of the circuit path, but the action that directly closes in this test is the sensitive relay’s contact.