Input ports (typically RJ45) that connect to sensors and probes (typically via CATx cable) and receive their reading (e.g. temperature, humidity, airflow sensors)

2-wire input ports that listen to connected device/sensor and wait to be triggered by them (e.g. flood sensor, door position sensor, etc.)

Output ports that trigger connected devicees to do their function (e.g. start dialing, turn alarm on, etc.)