DOKK / manpages / debian 11 / usbrelay / usbrelay.1.en
USBRELAY(1) General Commands Manual USBRELAY(1)

usbrelay - get information about and control USB HID relay devices

usbrelay envvar=[0|1]...

usbrelay without parameters shows information about found USB HID relay devices.

usbrelay with specified environment variables switches relays on or off.

/usr/share/doc/usbrelay/README.md.gz

This man page was written by Jan Dittberner <jandd@debian.org> for Debian systems (but may be used by others).