A liquid filter with a replaceable filter insert and a housing having a raw liquid inlet, a central clean liquid outlet, and an eccentric liquid discharge channel. In an embodiment of the invention, unique physical keys, or tokens, are installed at an access point and each client device of the network. The dielectric body with two different body portions, having different effective dielectric values, is displaceable between two end positions in a central, region of the device. The identification area, which should be visible when worn to third parties andor the person wearing the lenses, consists of markings such as colored bands or shaded areas in the region around the iris. The flap includes first projections which extend through the first openings into the chambers when the flap is closed to lock contacts held in the chambers.