The Wandel-Goltermann PCM4 Channel Measuring set is a microprocessor-controlled instrument for coding and decoding of telecommunications signals. It contains an analog signal generator, a digital signal generator, and analog receiver, and a digital receiver permitting measurements of PCM or VF signals. Internal self calibration features ensure high accuracy measurements. Automated testing routines of 24 measurement modes produce clear display results which can be exported to a plotter.