The Model 3310 Universal Digital Multimeter has 32 ranges covering ac volts and ac current, dc volts and dc current, resistance, and direct reading true rms dBm at lmW/600 n or 1 mW/900i2 reference. The multimeter may be operated from a 115 or 230 volt * ac line or from an internal rechargeable battery pack (The rechargeable nickel cadmium battery pack is optional). The batteries permit measurement with complete isolation from power line interference (infinite common mode rejection). Battery life is 20 hours on all functions except ac volts, ac current and dBm where life is minimum of 8 hours. The battery operated version may be operated from the ac power line while the batteries are being recharged. Charging circuits are internal to the multimeter. The bright fluorescent digital display consists of seven-segment numerical indicators which provide a maximum display of 1999. The display features include non-blinking buffered readout, automatic polarity indicator, automatically positioned decimal point and blinking overrange indication. The reading rate is twice per second. The blinking over range indication occurs when the reading exceeds 1999. Operator convenience and safety have been stressed in the design of the Model 3310. The equipment case consists of box-in-box construction with outer case connected to third wire ground. The input terminals and internal circuitry may be elevated 1500 volts from line ground without damage to the instrument. A color coded front panel is provided for ease in selection of the 32 ranges. High input impedance, guarded circuitry and true rms conversion minimize erroneous measurements. The direct reading dBm ranges provide conversion free dBm (1 mW/600i2 or 1 mW/900 n) measurements over a 110 dB range. Rugged construction, wide temperature operating range, exceptional overload specifications, and operator convenience make the Model 3310 ideal for laboratory, production line or field applications.