INTRODUCTION. The Models 179 and 179 20A are versatile Digital multimeter useful for measurement of ac and dc voltage, ac and dc current and resistance. The Model 179 20A is Identical to the Model 179 except for an added 20-ampere range. This extra range uses separate input terminals and allows continuous measurement of up to 15A ac/dc, or intermittent duty measurements up to 20A ac/dc. The Model 179 20A is treated by the exception method In this manual. That is, information headed by Model 179 20A applies only to the Model 179 20A. Information headed by Model 179 is common to both the Model 179 and the Model 179 20A. Ranges and accuracies for both models are listed in the Table of Specifications on page v. Ranges and functions are selected with front panel pushbuttons. The decimal point is also positioned by the selected range pushbutton. Polarity of the measured signal is automatically displayed.