|UPS DB9 Pin / Function
||PC Serial Port DB9 Pin / Function
|1 - Shuts down the UPS when held high for five seconds.
||4 DTR - Shuts down the UPS when held high.
|3 - Normally open, connects to ground when a power failure occurs.
||8 CTS - Indicates the loss of AC power.
|4 - UPS Ground
||5 Signal Ground
|5 - Normally open, grounded when UPS battery is low.
||1 DCD - Indicates safe computer shutdown when low.