The documentation states that
What is true?
However, description for _SERVICE internal variable states that…
/N If TCC was started as a service, use the /N option to prevent TCC from being closed on a Windows CTRL_LOGOFF_EVENT.
…which apparently implies that "/N" option not only prevents reaction to CTRL_LOGOFF_EVENT, but also enables TCC to report as a system service._SERVICE returns 1 if TCC was started as a service (TCC /N).
What is true?