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Updated: July 3, 2026
A storage battery is used to heat the filament of the tube, just as it is with a detector tube, and it can be of any make or capacity as long as it will develop 6 volts. The cheapest 6 volt storage battery on the market has a 20 to 40 ampere-hour capacity and sells for $13.00. The Battery Rheostat. As with the receptors a rheostat is needed to regulate the current that heats the filament.
A storage battery is used to heat the filament of the tube, just as it is with a detector tube, and it can be of any make or capacity as long as it will develop 6 volts. The cheapest 6 volt storage battery on the market has a 20 to 40 ampere-hour capacity and sells for $13.00. The Battery Rheostat. As with the receptors a rheostat is needed to regulate the current that heats the filament.
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