The Smart-UPS is a series of enterprise-level uninterruptible power supplies (UPS) made by American Power Conversion (APC). Most of the units have a SmartSlot (with the exception of SC and SMC series) which accepts an optional interface card providing features ranging from network connectivity to temperature and humidity monitoring. With the exception of RT and SRT series, Smart-UPS units are line-interactive UPS systems, only running their inverters when the grid power is unavailable. Models There are a few different variations in the Smart-UPS lineup. Management software All Smart-UPS units work with APC's proprietary PowerChute software which is available for a variety of operating systems. A free alternative to PowerChute is the Free software project APC UPS Daemon (Apcupsd), which supports Linux, Mac OS X, UNIX and Microsoft Windows operating systems and can run in stand alone or client-server modes. Legacy Smart-UPS (Not SMX, SMT, or SURTD series ) can also work with Network UPS Tools (NUT), a third party application, under Linux. The software is designed to safely and automatically shut down any connected computers before the batteries are depleted. Data interfaces As a way to provide UPS management, monitoring and automatic shutdown of attached equipment, all Smart-UPS models include at least one serial data interface (RS-232 or USB), while most models also have at least one SmartSlot expansion port, with the larger (and in many cases older) Smart-UPS models supporting two SmartSlots. Availability of more SmartSlots in a single Smart-UPS unit can be achieved via expansion modules such as the AP9600 and AP9604 models. Installing an add-on card into a SmartSlot will provide the UPS with additional features, capable beyond the default serial data interface. Early SmartSlot cards, such as the AP9605, provide SNMP functionality and Telnet access. The AP9606 and later cards add a web interface that can be used to configure and administer the UPS, as well as email-based alerting. The AP9617 and newer cards add 10/100Base-T connectivity, Secure HTTP, Secure Shell (SSH), RADIUS, SNMP Version 3, PCNS and syslog functionalities. The AP9612, AP9618, AP9619 and AP9631 models provide environmental monitoring when used together with APC temperature/humidity probes. The AP9618 model also provides out-of-band management via a modem connection in case the 10/100 Ethernet connection is down. SmartSlot cards remain powered by the battery even when the UPS is switched off, allowing the UPS to be remotely cold-started even in a power loss situation (presuming the network