APC UPS control system manual Voltage Signalling, 142

Voltage Signalling Features Supported by Apcupsd for Vari- ous Cables

The following table shows the features supported by the current version of apcupsd (3.8.5 or later) for various cables running the UPS in voltage- signalling mode.

Cable	Power Loss	Low Battery	Kill Power	Cable Discon-
				nected
940-0020B	Yes	No	Yes	No
940-0020C	Yes	Yes	Yes	No
940-0023A	Yes	No	No	No
940-0119A	Yes	Yes	Yes	No
940-0127A	Yes	Yes	Yes	No
940-0128A	Yes	Yes	Yes	No
940-0095A/B/C	Yes	Yes	Yes	No
simple	Yes	Yes	Yes	No

Voltage Signalling

Apparently, all APC voltage-signalling UPSes have the same signals on the output pins of the UPS. The difference at the computer end is due to different cable configurations. Thus, by measuring the connectivity of a cable, one can determine how to program the UPS. This is to be verified.

The signals presented or accepted by the UPS on its DB9 connector using the numbering scheme listed above is:

UPS Pin Signal meaning

1<- Shutdown when set by computer for 1-5 seconds.

2-> On battery power (this signal is normally low but goes high when the UPS switches to batteries).

3-> Mains down (line fail) See Note 1 below.

5-> Low battery. See Note 1 below.

6-> Inverse of mains down signal. See Note 2 below.

7<- Turn on/off power (only on advanced UPSes only)

Note 1: these two lines are normally open, but close when the appropriate signal is triggered. In fact, they are open collector outputs which are rated for a maximum of +40VDC and 25 mA. Thus the 4.7K ohm resistor used in the Custom Simple cable works quite well.

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