wire, selected to act as a fuse, soldered to supports on the back of the movement. Later versions had a calibrated, screw-in, fuse on the front panel. After copper oxide instrument rectifiers became available in the late 1920s, a 20-range "Universal" version of the AVOmeter was introduced in 1931 having both direct and alternating voltage current ranges. Unlike many similar multimeter designs, all Universal AVOmeters, with the exception of the short-lived "High Resistance (HR) AVOmeter" (c. 1948 - 1951), could measure up to either 10 A or 12 A (AC) depending on the model. From 1933, the number of available voltage and current ranges in Universal AVOmeters was doubled by incorporating a dual sensitivity movement circuit. The higher sensitivity was selected by a push button switch marked ÷2 (Divide by two) signifying that the pointer indication should be halved. For the Model 8, this feature was not used but the push button was retained for reversing the direction of deflection of the moving coil. A design feature of AVOmeters was simplicity of use and towards this end, all measurements could generally be made using only two input terminals. However, the AVOmeter HR had additional 2500 V (AC) and (DC) ranges which used the corresponding 1000 V ranges, and were connected through two additional terminals at the top corners of the front panel. This feature was continued in the Model 8 and, with an increase to 3000 V to match their 1 - 3 - 10 ranges sequence, in the Model 9, Marks II and IV and the Model 8 Mark V. The 3000 V ranges were deleted in the Model 8 Marks 6 and 7 due to concerns for compliance with contemporary safety standards. This also led to a significant cost saving by eliminating the high voltage multiplier resistors. As an ohmmeter the Model 8 Mark II measures from 1 Ω up to 20 MΩ in three ranges. The instrument has an accuracy of ±1% of FSD on DC current ranges, ±2% of FSD on DC voltage ranges, ±2.25% of FSD on all AC ranges and ±5% of reading (at centre scale only) on resistance ranges. Its maximum current draw of 50 μA at full-scale deflection (corresponding to 20,000 ohms per volt) is sufficient in most cases to reduce voltage measurement error due to circuit loading by the meter to an acceptable level. The AVOmeter design incorporates an electrical interlock