The TF2091B Noise Generator and the TF2092B Noise Receiver (when used together) make up the OA2090 White Noise Test Set (units are sold separately). The OA2090 permits measurement of intermodulation products and noise in multi-channel telephone link equipment. A noise signal generated by the instrument is used to simulate full traffic conditions in 12 channel up to 2700 channels. This signal is applied to the baseband circuit of the equipment under test and the noise in a narrow slot is compared in the loaded and unloaded states. The TF2091B Generator has available (at additional charge), a selection of high pass and low pass filters to restrict the noise to the required bandwidth and band-stop filters (also at additional charge), to create a slot within the band. When equipped with the proper filters (sold at additional charge) the TF2092B Receiver provides an automatic digital display of noise power ratio as the generator slot is switched in and out. The receiver will also display the relative channel power