The document describes only four alarm outputs and pin definitions, but does not detail the implementation principles.
1. The alarm interfaces are passive and can be set to Open or Close. By default, the interface is in Close state when an alarm is generated. The multimeter shows that the corresponding pin is short-circuited. When no alarm is generated, the interface is in Open state.
2. The four outputs are independent of each other. The automatic mode supports two outputs, and the manual mode supports four outputs.
3. ALMO1 and ALMO2 on the OSN 2500 SEI board are used as an example. 1 and 2 correspond to the positive and negative poles of critical and major alarms respectively. 3 and 6 correspond to the positive and negative poles of minor alarms and warnings respectively.