Malcom ... According to info faxed me from TrippLite: pin desc 1 "gnd", actually -12v derived from computer's SD pin-3 This feeds the emitter side of two opto isolators. 5 AC Fail, collector side of opto isolator, pulled up to +12 by 10K res in cable connected to computer's DTR pin-4. Connected to computer's CTS pin-8. -12 volts means AC Fail. 6 Low Batt, collector side of opto isolator, pulled up to +12 by 10K res in cable connected to computer's DTR pin-4.. Connected to computer's DCD pin-1. -12 volts means Low Batt. 2 Inverter shutoff, controlled by +12 from computer's RTS pin-7. Diode between UPS and computer, anode to computer. +12 volts from computer causes inverter to shut down. 4 Inverter shutoff, connected to computer's sig gnd pin-5. genericups 5 puts -12 on SD, +12 on DTR, and -12 on RTS. This all makes sense to me (and is compatible with measurements) for genericups 5 except for one bad thing: If I simulate AC Fail and Low Batt by feeding -12 volts to computer pins 1 and 8, my computer does not shut down. The daemon is running, but no cigar. ... Reed, alta@alta-research.com