The Model 8000B ratio can be calibrated directly against the 10 V Josephson Array or the ratio can be verified by measuring the normal and inverse ratio of two stable resistors using the 8000B Ratio Verification Box. The RVB contains a low thermal reversing switch and wiring so that the 8000B can be calibrated within its linearity specification. The program is built into the software and all measurements and data are stored to the measurement file. The software also performs the calculations of the ratio of the two resistors and the error of the bridge. Only the short term stability of the resistors is important.