The invention describes an apparatus for the filtration of liquids and an associated filter cartridge 100, the correct seating of which is ensured and can be established by the user. The second magnetic conductor is magnetically attracted to the first magnetic conductor to establish an electrical conductive path between the first and second magnetic conductors. The base of the spectrum converter is a phosphor powder Mg3Si2O8:Me+2,+3Hal2,3, and a radiation with a wavelength from 520 nm to 650 nm can be obtained by changing the proportion of these ingredients. When the navigation system is restarted, the calculated route will be reproduced based on the direction codes retrieved from the backup memory, thereby enabling to continue the route guidance operation to guide the user the destination.