5.2.5 - Negative feedback amplifier
Schematic of the negative feedback circuit

In one of the most fundamentals developments in the history of communication, Harold S. Black discovered that the negative feedback could be applied to an amplifier to minimize distortion over a wide band  of frequencies  and achieve gain stabilization at the same time. Please see the homage from Bell Telephone Laboratorie to the enginer Harodl S. Black winner of the “Lame Medal”. It is interesting to notice that the Black’s researches are different form Harold Alden Wheeler, who had earlier used the properties of the negative feedback for controlling the audio output volume over a wide frequency range of RF signals level in AM radios. Wheeler  work was developed when working at Hazeltine Company in 1926.

Under the title: "A man win's a medal.... and strengthens a Philosophy." The engineer views hopefully hitherto unattainable, was an homage from Bell Laboratories to the engineer Harold S. Black winner of the Lame medal circa 1960 for his pioneer achievements in many contributions for radio communication  certainly including the development of the negative feedback circuit.