9 PIN D-SUB Female Connector at the UPS.
The Minuteman Alliance Series (models A300 through A2000) by Para Systems, Inc. provides a DB9 female connector for external UPS monitoring. The interface uses open-collector (relay-simulating) outputs on most pins rather than RS-232 logic levels; the sole RS-232 signal is the input on pin 6 used for software shutdown. The Alliance Series is distinct from the later XRT/Enterprise Series, which uses RS-232 logic levels on most pins and carries a different pinout entirely. All Alliance models except the A300 include the monitoring interface.
| Pin | Description |
|---|---|
| 1 | Unused |
| 2 | Battery power |
| 3 | Unused |
| 4 | Common (same as 7) |
| 5 | Low battery |
| 6 | RS-232 level shutdown |
| 7 | Common (same as 4) |
| 8 | Ground level shutdown (A500 and above, reserved on <A500) |
| 9 | Reserved |
Signals
- Pin 1 — No connection.
- Pin 2 — Open-collector output; closes to pin 4 (common) when the UPS switches to inverter (battery) mode, indicating commercial AC power has failed.
- Pin 3 — Not used.
- Pin 4 — Common ground return for pins 2, 5, 6, and 8.
- Pin 5 — Open-collector output; closes to pin 4 at low battery warning.
- Pin 6 — RS-232 high-level input (9–12 VDC) to the UPS; commands shutdown of the inverter whilst on battery power.
- Pin 7 — Common; electrically the same as pin 4.
- Pin 8 — On A500 and larger models: short to ground turns off UPS output. No connection on smaller models.
- Pin 9 — Reserved.
Notes
- Pins 2 and 5 use open-collector outputs (simulated relay closures to common) rather than RS-232 voltage levels.
- Pin 6 accepts an RS-232 high level (>9 V) to shut down the UPS, but only whilst it is running on inverter (battery) power.
- Shorting pin 8 to ground (pins 4 or 7) commands shutdown of the UPS output on A500 and larger models.
- Pins 4 and 7 are electrically identical; either may be used as the common return.
- The A300 model does not implement the monitoring interface; all other Alliance models (A425 and above) do.