The 82 is a 4-pin UX-base mercury-vapor full-wave power rectifier vacuum tube introduced in 1932. Engineered for intermediate-power supply applications in vintage radio receivers and audio amplifiers, it uses ionized mercury vapor to provide exceptional voltage regulation with a constant 15-volt internal drop under varying current loads. Designed with an ST-12 shoulder glass envelope and dual directly heated filaments, it operates on a 2.5V filament rating. The 82 serves as the lower-voltage, 2.5V filament counterpart to the heavy-duty type 83 rectifier. Available NOS and tested used.