This transceiver is a conventional crystal oscillator and power amplifier on transmit, but with a flick of a switch it transforms into a direct conversion receiver in which the triode becomes oscillator and mixer while the pentode becomes an audio amplifier. It’s simple, and the video below the break explains it in great detail. We’re not sure whether or not it could unintentionally radiate in receive mode, but we’re guessing the energy would be tiny.