The Keysight 8517B test set has an architecture that develops a separate reference channel for each incident port. RF switching is done with a built-in electronic switch. For active device measurements, the test sets include the ability to apply dc bias (external) to the test port center conductors. Also available are two 60 dB step attenuators, which allow control of the port 1 and port 2 signal levels. Option 007 high dynamic range configuration.