|  | 8.11 | Network Power Supply Issues: Surge Suppressors and Uninterruptible Power Supply (UPS) Functions
| 8.11.6 | UPS: differences in UPS features
A number of vendors have developed UPS systems. You will find that they differ in the following ways: the power storage capacity of the batteries; the power delivery capability of the inverter; and the operational scheme (whether they operate continuously, or only when the input voltage reaches a specific level). Also, the more features a UPS has, the more it costs.