This cable can only be used on voltage-signalling UPSes, and provides the On Battery signal as well as kill UPS power (and may be Low Battery signal).
| UPS Signal Name | DB-9 Male (UPS end) | DB-9 Female (PC end) | PC Signal Name |
| Shutdown | 1 | 4 | DTR |
| AC Fail | 2 | 8 | CTS |
| Common | 4,9 | 5 | GND |
APC Part# - 940-0020B (investigated by apcupsd team)
Signal Computer UPS
DB9F DB9M
CTS 8 -------------------- 2 On Battery
DTR 4 -------------------- 1 Kill power
GND 5 ---------------*---- 4 Ground
|
--- *---- 9 Common
DCD 1 ----|///|----------- 5 Low Battery
|\|
RTS 7 ----|///| (probably a
--- semi-conductor)
Note: sides swapped.
Full scheme of 940-0020C isn"t yet known.
APC Part# - 940-0020C (investigated by apcupsd team)
Signal Computer UPS
DB9F DB9M
CTS 8 -------------------- 2 On Battery
DTR 4 -------------------- 1 Kill power
GND 5 ---------------*---- 4 Ground
|
*---- 9 Common
RTS 7 -----[ 93.5K ohm ]----- 5 Low Battery
or semi-conductor
Our users reports that the 20C is designed to mimic a mouse movement when it received an on battery signal from the Back-UPS. Therefore the computer will wake up and shutdown properly. The 20B cable does not have this functionality.
