From philo@3:633/280.2 to All on Sun Jun 2 05:46:31 2024
The 5v tube filaments ran from a 6v car battery which could be recharged
at the local (car) service station.
The high voltage batteries lasted a fairly long time due to low current requirements.
FWIW: my house was not electrified until 1932 so if the owner had a
radio, it would have been battery powered.