Many devices including cameras and recorders support audio recording using external microphones via an audio input or built-in microphone. Audio can be set to record along with video, offering both audio and video evidence.
Certain cameras & recorders have alarm inputs which will trigger when set up to identify potential threats
Power over Ethernet (PoE) allows power to be delivered via the Ethernet cable, removing the requirement for dedicated power supplies. Many NVRs & Network Switches support PoE allowing these devices to deliver power to PoE capable IP cameras via the network infrastructure itself