Troubleshooting
61287802F1-34B
51
Revision B
7.4 UPS Communication Signals
The communication signals of the UPS are isolated from the internal circuitry via open
collector opto-coupled transistors. The connection
SIG RTN
(Signal Return) is a common
return point for all communication signals. In the typical application, the attached equipment
digital ground connects to Signal Return, and pull-up resistors turn the open collector signals
into logic levels.
A pinout of the communication signals is shown in
Table 15. UPS Communication Signal Descriptions
Signal
Description
+12 VDC
Vo+ (+ Voltage output)
12V RTN
Return path for +12 VDC
SIGNAL RETURN
Signal return
ON BATTERY
Low when operating from utility line
Open when operating from battery
REPLACE BATTERY
Low when battery is charged
Open when battery fails self-test
BATTERY MISSING
Low when battery is present
Open when battery is missing
LOW BATTERY
Low when battery is near full charge capacity
Open when operating from a battery with less than 20% capacity
