| Pin# | Signal Type | Function |
| 1 | RS-232 Earth Ground | Signal Common for all RS-232 port signals (earth ground referenced) |
| 2 | RS-232 Transmit Output | Serial communication mode - output signal line. |
| 3 | RS-232 Receive Input / Shutdown | Serial communication mode - input signal line. Contact Closure mode - shuts down UPS if signal is held high (RS-232 level) for 200 milliseconds while UPS is operating in battery mode. |
| 4 | AC Line Fail (normally closed) | Contact Closure mode - opened when AC line fails and UPS is operating in battery mode (breaks connection between Pin#4 and Pin#5). |
| 5 | Contact Closure Common / RS-232 Common | Signal Common for all Contact Closure group / RS-232 Signal Common line. |
| 7 | Low Battery (normally open) | Contact Closure mode - closed when remaining "on-battery runtime" drops below the under-defined time limit (makes connection between Pin#7 and Pin#5). |
| 9 | AC Line Fail (normally open) | Contact Closure mode - closed when in battery mode (makes connection between Pin#9 and Pin#5). |
