12BT7A

Dual Triode and High-Mu Single Triode Multi-Unit Tube, featuring a 12.6V heater filament. It integrates three independent triode elements within a single envelope, optimized to simultaneously manage FM stereo multiplex decoding, phase inversion, and audio voltage pre-amplification tracks, housed in a standard 9-pin miniature glass envelope (Noval, T-6.5 bulb).