You are staring datasheet cross reference the Apogee Labs, Inc in pdf document that is listed in Library Reference datasheet archive category. This Apogee Labs, Inc pdf file was acquired via www.apogeelabs.com
Content : A Good Automatic Gain Controlled Agc Amplifier In The Circuit Reduces These Problems To Manageable Levels. The Apogee Labs Model 2173, Shown In. Figure 1