The 14R7 is an 8-pin lock-in base (Loktal) multi-unit tube containing two independent detector diodes and a semiremote-cutoff pentode section. Designed for radio receiver applications, it combines AM signal detection, automatic volume control (AVC) rectification, and RF/IF or audio frequency amplification within a single envelope. It operates with an indirectly heated cathode on a 12.6V / 14.0V heater supply. Sylvania, RCA, GE, and Philco manufactured the 14R7 to RETMA specifications using T-9 glass envelopes. It is functionally equivalent to the 7R7, differing only in its heater voltage rating.