Every UPS on this page falls into one of two families. Line-interactive UPS keeps the load running directly off mains power and only switches to battery when it senses a real disturbance the setup behind most desktop, network, and small-office installs, valued for its simplicity and low running cost. Online double-conversion UPS never lets the load touch raw mains at all: it converts incoming AC to DC and back to AC continuously, so there's zero transfer time when power drops the standard for servers, medical equipment, and anywhere a flicker can't be tolerated. Beyond the core technology, units can be built out as modular stacks for scalable capacity or hardened for outdoor deployment. Which one fits a site comes down to how much downtime the load can absorb.