Originally created by the Federal Television Corporation, production of the AM-864 started in 1954 and lasted around a decade. The AM-864 saw service in the US Army and US Air Force during the Korean War, as a AM broadcast peak modulation limiter. The AM-864 is a simple, rugged device that accepts 600 ohm balanced or unbalanced line-level signal, offers a single front-panel input-attenuator control, and compresses the output level at a 10-to-1 ratio once the threshold point is reached. The output is also 600-ohm balanced or unbalanced, and it offers a maximum 36db of gain. Want to build your own? Here's LINK-1 and LINK-2 to get you started.