| Pin | Signal | Description |
| 1 | Shut Down (dumb mode) / RS-232 RX In (smart mode) | Set high for 1-5 sec to activate shutdown. |
| 2 | Line Fail (dumb mode) / RS-232 TX Out (smart mode) | On-battery power (normally low but goes high when the UPS switches to batteries) |
| 3 | Line Fail signal | Mains down (normally low but goes high when line fail) |
| 4,9 | GND | Ground, chassis |
| 5 | Low battery signal | (normally low but goes high when low battery) |
| 6 | Line fail signal | Inverse of pin 2 Line Fail signal |
| 7 | UPS Turn-on/off signal | (on advanced UPSes only) |
| 8 | Unregulated +24 Vdc Out ?? |
