A common-base equivalent circuit of alloy-type transistors containing a multi-element representation of collector capacitance and base resistance has been verified by a variety of measurements. As a consequence it is shown why different methods of measuringrbb', the single-element representation of base resistance, do not lead to consistent results. However, provided that suitable values are chosen forrbb'and forcc, the total collector capacitance, a simpler equivalent circuit containing these two elements is acceptable over the usable frequency range.