The 3BN6 is a 7-pin miniature gated-beam discriminator vacuum tube designed specifically for FM sound detection, limiter, and audio driver service in radio receivers and audio equipment. Featuring a 3.15V heater rating with controlled warm-up time for series-filament radio circuits, it operates as a combined FM limiter and detector, directly producing demodulated audio output without requiring preceding limiter stages. Available in new old stock (NOS) and tested used conditions.