9 PIN D-SUB FEMALE at the UPS
The ONLINE USV-Systeme AG Yunto P series (250, 500, 750, and 1250 VA models) provides a 9-pin D-sub female connector on the rear panel for interfacing with a host computer. Unlike conventional RS-232 serial ports, this interface uses potential-free optocoupler contacts rather than RS-232 voltage levels: an external DC supply (between +5 V and +50 V) must be connected to pin 4 and pin 5 to bias the optocouplers before any status outputs can operate. Pins 1, 8, and 9 present normally-open or normally-closed relay-style contacts that short or open to pin 5 (ground) in response to mains-failure or low-battery conditions, whilst pin 7 accepts a positive DC voltage to trigger a graceful UPS shutdown. The interface maximum rating is 50 VDC at 50 mA per contact.
| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | Battery Mode | out | This pin is shorted to PIN 5 (ground) if the mains power supply fails or is out of tolerance. (NORMALLY OPEN) |
| 2 | - | - | - |
| 3 | - | - | - |
| 4 | Power+ | IN | Positive DC voltage input (+5 V to +50 V max) for optocoupler bias; connect to Pin 5 (GND) to enable signal outputs on pins 1, 8, and 9 |
| 5 | Ground | - | Ground terminal and common root of contacts at PIN 1, 8 and 9 |
| 6 | - | - | - |
| 7 | UPS shut-down | IN | If a positive signal level (+5V to +12V DC) is applied, the UPS system switches off (PIN 5 is ground) |
| 8 | Battery Capacity Low | OUT | This pin is shorted to PIN 5 (ground) if the batteries have been discharged to such an extent that the remaining stored energy time is less than 2 minutes. (NORMALLY OPEN) |
| 9 | Battery Mode | OUT | The connection between this pin and PIN 5 (ground) is disconnected if the main power supply fails or is out of tolerance. (NORMALLY CLOSED) |
Notes
- Direction is relative to the UPS unit.
- This is an optocoupler contact-closure interface, NOT an RS-232 serial port. No RS-232 voltage levels are present on any pin.
- Pin 4 must be driven with an external DC supply (+5 V to +50 V, max 50 mA) referenced to pin 5 before any output contacts (pins 1, 8, 9) will operate.
- Pin 7 shutdown input requires a positive DC signal of +5 V to +12 V (referenced to pin 5) to command the UPS to switch off.
- Pins 2, 3, and 6 are unassigned and should not be connected.
- The 250 VA model is not explicitly documented in the available manual; the pinout is expected to be identical to the 500/750/1250 VA variants.
Signals
- Battery Mode (pin 1) — Normally-open contact; shorts to pin 5 (GND) when mains supply fails or is out of tolerance. Requires pin 4 bias supply to operate.
- Ground (pin 5) — Common reference terminal for all signal contacts and the pin 4 bias supply return.
- Power+ (pin 4) — Positive DC voltage input for optocoupler biasing. Must be connected with pin 5 as the return; no signals on pins 1, 8, or 9 will function without this supply.
- UPS shut-down (pin 7) — Shutdown input; applying +5 V to +12 V DC here (with pin 5 as reference) commands the UPS to power off gracefully.
- Battery Capacity Low (pin 8) — Normally-open contact; shorts to pin 5 when battery runtime falls below approximately 2 minutes.
- Battery Mode (pin 9) — Normally-closed contact; the connection to pin 5 opens when the mains supply fails or is out of tolerance (complement of pin 1).