The Cisco PWR-3900-POE Power Supply is an internal AC power module with integrated Power over Ethernet designed for Cisco ISR 3925 and 3945 routers. It provides router system power and PoE for connected devices, accepting 100–240V AC input at 50–60 Hz and serving as a replacement or upgrade for Cisco ISR 3900 Series deployments. Common applications include enterprise branch networks and unified communications environments where reliable router power and PoE support are needed; related replacements include Cisco PWR-3845-AC-IP Power Supply.
