Universal Bridge B221 operates at audio frequencies and provides accurate values for all types of electrical components over an extremely wide measurement range. The internal Standards are of conductance and capacitance, but the Bridge measures positive or negative conductance or resistance, together with capacitance or inductance. Two displays provide, simultaneously but without any interaction, values for the resistive and reactive terms of any Unknown, including all cyphers, the decimal point and the units of measurement. The Bridge has an internal source and detector operating at a fixed frequency (normally 1592 c/s to simplify calculations involving 2nf) but can be operated with an external source and detector at any audio frequency. Suitable instruments for this purpose include the Wayne Kerr Audio Signal Generator SI21 and (above 100 c/s) Waveform Analyser A32I. Full details of these instruments are available separately: their use with the B22I Bridge is described in this Manual.