To my surprise I found an information this UPS produce full sine wave when on-battery. That's a nice feature!
Right now it powers my internet access modem and the NAS only. The next challenge is to connect it with the internal network to propagate an information (SNMP) about power failure. It would give the NAS a chance to shut down gracefully before UPS is out of energy.
APC Smart UPS 700 can communicate with the outside world in a proprietary protocol through its DB-9 RS232 (2400 baud) connection. However you cannot use a typical DB9 RS232 cable to connect to it. An adapter is required for this because the usual 2-3 pins have been mapped to 2-1 pins. Here is a wiring diagram:
PandaBoard which has been lying on my shelf much over a year. I installed Ubuntu 12.04 on PandaBoard and setup apcupsd as a monitoring hardware. Installing Ubuntu at PandaBoard and optimizing it is a long story worth of a separate article.