I-9301 Addressable Single I/O Module works in two-wire mode and four-wire mode.
In four-wire mode, on receiving start command from the fire alarm control panel (FACP), it will close the output relay to output 24VDC and illuminate the Active indicator. If there is short, open circuit, or power down, the module can check failure and report it to the FACP.
In two-wire mode, on receiving start command from the fire alarm control panel (FACP), it will close the output relay to output normally-open close contact signal and illuminate the Active indicator.