The 6F7 is a multi-unit vacuum tube introduced in the 1930s combining a pentode and a triode within a single metal envelope, engineered for use as a combined detector, oscillator, and amplifier in superheterodyne radio receivers. It features an external top control grid cap for the pentode section to minimize interelectrode capacitance and maximize shielding. Operates on a 6.3V heater and fits standard 8-pin octal sockets. Available NOS and tested used.