Dahua Analog 4 Channel Full-channel AI-Coding 4K Recording (DH-XVR1B04H-I) - Main Processor: Industrial-grade processor, Ports: Audio Input: 1-channel RCA, 4-channel BNC (Coaxial Audio), Audio Output: 1-channel RCA, Two-way Talk, HDD Interface: 1 SATA port, up to 16 TB. The maximum HDD capacity varies with environment temperature, USB: 2 USB ports (USB 2.0), 1 x HDMI, 1 x VGA, Network Port: 1 (10/100 Mbps Ethernet port, RJ-45), OS: Embedded Linux