The measuring system must provide a means for applying bias to the transistor under test. The bias
system must be such as not to influence the accuracy of the measurements. The signal applied by the
measuring system to the transistor must be sufficiently smail to satisfy the “small-signal conditions”
defined in 1.2. In addition, any spurious signals which might appear at the transistor terminals, and in
particular, the local oscillator feedthrough when a superheterodyne receiver is used, must be kept at
least 20 dB * below the specified small-signal conditions.