http://qkpm2ov2rjhjkhfsftskqho77uj5rewd5y44unkf6cb7tdhaxwcvh2id.onion/books/apc/APCUPSD%20User%20Manual.html
APC calls this language "UPS-Link". Originally
introduced for Smart-UPS models (thus the name 'apcsmart'), this
class of UPS is in decline, rapidly being replaced in APC's product
line by USB and MODBUS UPSes. usb A USB UPS speaks a universal well defined control
language over a USB wire.