Arcturus 071H
AC Audio Output Triode
1928

The 071H was a special indirectly heated version of the 071. The midpoint of the heater is connected to the cathode. This arrangement allowed the commonly used hum balance pots in AC receivers to function normally. The internal construction is quite different from the standard '71 and the heater drew 1.2 amps at 5 volts. This tube was made only for a matter of months.