Hazeltine Research Inc. in Chicago was a subsidiary of Hazeltine Corp. in Little Neck, New York. The various Hazeltine companies did research in radio and television and built up a patent library, similar to RCA's radio patent pool. It later engaged in military electronics, and is currently a division of BAE Systems.
Hazeltine 1953 A Four-Stage 40 Mc IF Amplifier Report No. 8015 - A high performance TV IF amplifier for the new 40 MHz IF frequency.
Hazeltine 1953 Three-Stage 40 Mc IF Amplifiers Report No. 8016 - A lower-cost version of the 40 MHz TV IF amplifier with two versions of the output stage.