Types of sensors that come with the monitoring appliance, either internally or externally

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 on/off-type ports that listen to a connected device/sensor and wait to be triggered by them, typically stating either an ON or OFF condition (e.g. flood sensor, door position sensor, UPS, etc.). Some dry-contact ports can also function as output ports.

3-wire ports that accept an analog value e.g. 0-5VDC or a 4-20mAmp signal from a connected device

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