 8 ordinary D cells would operate the radio for >500 hours, as opposed to ~150 hours for the tube models and their massive A/B battery.The 3000 was also introduced as battery-only.Later the 1000-1 and 3000-1 models were introduced with provision for an external power using what was one of the first "wall wart" type power supplies - a transformer, rectifier, and filter capacitor in a box with AC line connector that plugged into and hung from the wall socket.