The Sola/Hevi-Duty Uninterruptible Power Supply product line consists of four topologies and classes of power protection: DC topology , Off-Line topology, Line-Interactive topology, On-Line topology DC topology provides cost effective, efficient back-up power for 24 V DC applications. The SolaHD DC UPS will support the load during AC power loss or power supply failure. Off-Line topology (also called stand-by) is a cost-effective UPS choice for small, less critical, stand-alone applications such as isolated PLC, PCs and peripherals. Network communications are a useful option. Line-Interactive topology provides highly effective power conditioning plus battery back-up. This is particularly applicable in areas where power outages are rare, but where there are frequent power fluctuations. Network communications are available and sometime necessary. The On-Line alternative provides the highest levels of power protection, conditioning and power availability. True on-line topology is accomplished with double conversion technology. Network communications are often necessary to protect mission-critical applications.