The 861A Generator-Detector is an audio frequency generator and a sensitive low-noise detector ganged together as a variable-frequency signal source and tuned null indicator over the audio frequency range from 20Hz to 20kHz in three ranges. Generator: 0-200 V (4 ranges) with less than 2% distortion; 0.04-ohm to 10 kohms (4 ranges) Detector: Full scale deflection with 1 ?V or less input; approx. 1 Mohm shunted by 80 pF on most sensitive range