APC SU1400XLT User Manual download pdf (Page 76)

CTS 8 ----------*--------- 5 Low Battery

GND 5 -------------------- 4 Ground

DCD 1 -------------------- 2 On Battery

RTS 7 -------------------- 1 Kill UPS Power

List of components one needs to make the Simple cable:

1. One (1) male DB9 connector, use solder type connector only.

2. One (1) female DB9/25F connector, use solder type connector only.

3. One (1) 4.7K ohm 1/4 watt 5% resistor.

4. rosin core solder.

5. three (3) to five (5) feet of 22AWG multi-stranded four or more conductor cable.

Assembly instructions:

1. Solder the resistor into pin 4 of the female DB9 connector.

2. Next bend the resistor so that it connects to pin 8 of the female DB9 connector.

3. Pin 8 on the female connector is also wired to pin 5 on the male DB9 connector. Solder both ends.

4. Solder the other pins, pin 5 on the female DB9 to pin 4 on the male connector; pin 1 on the female

connector to pin 2 on the male connector; and pin 7 on the female connector to pin 1 on the male

connector.

5. Double check your work.

We use the DTR (pin 4 on the female connector) as our +5 volts power for the circuit. It is used as the Vcc

pull-up voltage for testing the outputs on any "UPS by APC" in voltage-signalling mode. This cable may

not work on a BackUPS Pro if the default communications are in apcsmart mode. This cable is also valid

for use on a ShareUPS BASIC Port. It is reported to work on SmartUPSes, however the Smart Cable

described above is preferred.

To have a better idea of what is going on inside apcupsd, for the SIMPLE cable apcupsd reads three

signals and sets three:

Reads:

CD, which apcupsd uses for the On Battery signal when high.

CTS, which apcupsd uses for the Battery Low signal when high.

RxD (SR), which apcupsd uses for the Line Down

signal when high. This signal isn't used for much.

Sets:

DTR, which apcupsd sets when it detects a power failure (generally

5 to 10 seconds after the CD signal goes high). It clears this signal if the CD signal

subsequently goes low -- i.e. power is restored.

TxD (ST), which apcupsd clears when it detects that the CD signal

has gone low after having gone high - i.e. power is restored.

RTS, which apcupsd sets for the killpower signal -- to cause the UPS

to shut off the power.

Please note that these actions apply only to the SIMPLE cable. The signals used on the other cables are

different.

Finally, here is another way of looking at the CUSTOM-SIMPLE cable:

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APC SU1400XLT User Manual Page 76