A PoE switch switches the traffic and delivers DC power over the same cable, so cameras and access points install without a power outlet at each point. RULE builds 100M and gigabit models from 4 to 24 ports, sized for real camera loads.
Add up what each device draws — a dome camera 6–12 W, a PTZ with heater and IR 25–30 W, an 802.11ac access point 12–20 W — then keep 20–30% headroom and compare with the switch's total PoE budget, not with “PoE on every port”. A 360 W 16-port unit runs sixteen 15 W cameras, not sixteen PTZs.
Copper stops at 100 m; longer runs need fibre, so plan an SFP uplink and match the module to the distance. On larger sites, split cameras across two switches joined by fibre instead of chaining one uplink.
Starting points: RS1008K for small cabinets, RS1016K for 16-port groups.