If you lose the master password, you may need to perform a hard reset. On many units, this involves powering down, holding the * or # key, and powering back up, but check your specific unit's wiring diagram first.
: The language can be dense, making initial setup for simple "home" use feel more complicated than necessary. mk098e manual better
Since the manufacturer rarely updates their PDFs, the best way to get a is through user-generated knowledge bases. Do not rely on random blog posts. Instead: If you lose the master password, you may