The cadet left the switchboard to get a radio, and returned with a battery portable valve radio. Although quite expensive to buy and to operate, there was a very large market for battery portable valve radios and they were very common throughout the valve era. Batteries were the only possible power supply, because valves with "heaters" used with AC mains power electricity appeared after the D.C. battery types. Texas Instruments in 1952 demonstrated their all-transistor AM radios, but their performance was well below that of equivalent battery tube models. In August 1953 a workable all-transistor radio was demonstrated at the Düsseldorf Radio Fair by the German firm Intermetall. If you had no knowledge of the existence of battery portable valve radios in 1942, you might mistakenly believe that the portable radio is a fake, because the portable transistor radio was not invented till 1952.
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05/03/2025 alle ore 08:56
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