| UPS Signal Name | DB-9 Male (UPS end) | DB-9 Female (PC end) | PC Signal Name |
| Ground | 1 | 3 | |
| AC Fail | 5 | 8 | CTS |
| LOW BATT | 6 | 1 | DCD |
| Inverter shutoff- | 4 | 5 | GND |
| Inverter shutoff+ | 2 | 7 | this wire includes one 1N4148 or 1N4149 diode |< |
Pin 4 at the PC end (DTR) connected by R1 10kOhm to pin 8 (CTS) and by R2 10kOhm to pin 1(DCD)

