How does the internal loc switch work on PMA Blueport controllers?

If the switch is in the closed position, all levels can be accessed from the front keypad without restrictions. This applies to all PMA PMA Blueport products (KS92-1, KS90-1, KS52-1, KS50-1, KS42-1, KS41-1, KS40-1).

If it is in the open position, the visibility and access rights to parameters are set using the Blue Control software (in the “Other” section of the Configuration section).
From there you can Block (disable) a menu level so that it cannot be seen or accessed, and for the levels that are enabled, you can choose to have a password or give free access (which is the same as having the switch open).

Despite the above, you can use Blue Control to individually hide parameters that would otherwise be in a visible menu. Hidden parameters are even hidden if the switch is closed.
Similarly, you can copy a hidden/blocked parameter into the extended Operation level and if you enable this menu, you can edit the parameters copied there (without a password).