Mirtone 7516‑U902 is a QuickStart industrial fire alarm control panel that interfaces with smoke detectors, manual pull stations and zone relays via a 24 V DC power supply and serial/Modbus links. Common failure modes include loss of power or voltage drop on the 24 V rail, corrupted configuration memory (often after a power interruption), and communication errors between the panel and connected devices (e.g., bad RS‑485 termination). Initial troubleshooting should verify that the panel’s main power supply is delivering clean 24 V DC, inspect all wiring for loose or corroded connections to detectors and relays, and review any displayed error codes or LED status indicators on the front panel.[oss-gpt-20b]