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WHAT’S THE FREQUENCY? Speaking of tubes, the translucent beauty of the ones in the Atwater Kent Number 4333 “Compact” Receiver is so great as to render its functionality almost superfluous—which is a good thing. Shortly after this device was introduced in September 1923, the range of U.S. broadcast frequencies was expanded, rendering it almost useless. Today the 4333 is highly prized by vintage radio collectors.