A board is supplied on which are mounted a variety of inductances capacitors and resistances with individual banana plug connections. A General Radio audio-oscillator supplies the voltage for the study. A low resistance, about a hundred ohms, is placed in series with each circuit that is to be studied. Voltage across this low resistance is a measure of the magnitude and the phase of the current. It is displayed on one trace of a dual-trace oscilloscope. The voltage from the audio-oscillator is displayed on the other trace of the oscilloscope. Thus, for each circuit or combination of circuit elements, one can study both the voltage and the current, and thus measure both the impedance and the phase angles.