6 pin RJ12 (6P6C) female connector at the UPS
| Pin | Function |
|---|---|
| 1 | Shutdown input (sustained high initiates shutdown) |
| 2 | On-battery output (RS-232 TXD in smart mode) |
| 3 | Open-collector status output |
| 4 | Signal common |
| 5 | Open-collector status output |
| 6 | Open-collector status output |
The APC Back-UPS Office uses a proprietary 6-pin RJ12 (6P6C) female socket on the UPS chassis as its computer interface port. APC defines this as a “basic port”, shared across the Back-UPS and Back-UPS Pro product families and the Smart-UPS v/s line, providing simple-signalling operation without a full RS-232 serial data protocol. The port connects to a PC serial port via the APC cable 940-0119A, which terminates in a DB9 female connector at the computer end. The interface was designed for use exclusively with APC power-management software and accessories, and APC describes the port as proprietary.
Signals
- Pin 1 — Shutdown input: a sustained high RS-232 level initiates UPS shutdown (after approximately 1 second on Back-UPS models)
- Pin 2 — On-battery output: transitions low-to-high at RS-232 levels when the UPS switches to battery; normally low; also serves as RS-232 TXD in smart mode
- Pin 3 — Open-collector status output; chassis-referenced, rated ≤25 mA, ≤+40 Vdc; use only pin 4 as common
- Pin 4 — Signal common (chassis ground reference for open-collector outputs)
- Pin 5 — Open-collector status output; chassis-referenced, rated ≤25 mA, ≤+40 Vdc; use only pin 4 as common
- Pin 6 — Open-collector status output; chassis-referenced, rated ≤25 mA, ≤+40 Vdc; use only pin 4 as common
Notes
The RJ12 (6P6C) connector is mechanically identical to an RJ11 housing but uses all six contacts. The APC cable 940-0119A adapts the UPS-side RJ12 to a DB9 female at the PC serial port. Pins 3, 5, and 6 are open-collector outputs and must reference pin 4 as their common return; do not use the PC-side DB9 shell ground as the signal common for these pins. The port is not compatible with standard RS-232 serial cables or generic USB-to-serial adaptors without the APC-specific cable wiring. APC states the interface is intended solely for use with APC software, cables, interface kits, and accessories.
References
- Application Note #12: The APC Computer Interface Port — American Power Conversion (APC), 2004