The Model 410B is a laboratory quality volt-ohm-meter that has been especially designed for making accurate voltage measurements in the frequency range from 20 cps to over 700 me per second, with useful indications at frequencies as high as 1500 megacycles. The instrument has full scale a-c ranges es of 1, 3, 10, 30, 100, and 300 volts with an input resistance of 10 megohms at low frequencies, shunted by 1.5 µf. Dc ranges are provided with full scale values of 1, 3, 10, 30, 100, 300 and 1000 volts. The dc input resistance is approximately 122 megohms on all ranges. The ohmmeter ranges have mid-scale values of 10, 100, 1,000, 10,000, 100, 000, 1, 000, 000, and 10, 000, 000 ohms. Accurate resistance readings from 1 ohm to 500 megohms are easily made. The meter scale calibration is very straight forward. All dc voltage ranges and ac ranges 10 volts and above are read on two black scales calibrated 0-1 and 0-3. Due to non linearity of the diode at very low voltages, the 1 and 3 volt ac ranges are read on special, separate, red scales.