Agilent / HP / Keysight 3552A

The Agilent 3552A is a Transmission Test Set.

The 3552A is designed to be used in testing telecommuncations equipment. It has calibrated test signals while making frequency or level measurements on voice frequency systems, program systems and data circuits, all at the same time. Some of the features are dial and hold capabilities, input impedances of 150 ohms, 600 ohms, and 900 ohms, a choice of four noise weighting filters and has digital readout of level or frequency.