The invention relates to a filter mat, which is used in applications where it filters the flows of contaminated air that pass through it. A path signature, similar to a pathname, is stored in a database system in association with data for the node identified by the pathname. Each of the semiconductor components is connected in an efficient heat-conducting manner to a heat sink provided on an opposite side of the carrier part by way of a heat conducting means that is fed through an opening in the carrier part. The magnetic flux leaks from the master medium between adjacent magnetic pieces on the master medium. The invention subject matter is useable in systems characterized by contact operation, as well as by quasi-contact and noncontact operations, in relation to the recording surface in an information recording medium.