 The function principle of a SQUID is based on macroscopic quantum interferences of electric currents, arising in superconducting circuits (loops) with tunnel junctions.Resistance bridges based on CCCs are used for the comparison of electrical resistances, in particular if highest-precision measurements are required, as there is the traceability of the resistance unit to the quantum Hall effect (QHE).In this way, measurements connecting standard resistors ranging within 1 ohm up to 10 kΩ to a QHE resistor of 12.9 kΩ are performed at several national institutes of metrology as, for instance, the National Institute of Standards and Technology (NIST, USA) or the Physikalisch-Technische Bundesanstalt (PTB, D).