English: A typical antique vacuum tube radio from the 1920s, with horn loudspeaker (right) and batteries to run it. The central unit is the Paragon Model RN-10 regenerative receiver made by Adams-Morgan Co. The unit on the left is a 3 tube audio amplifier unit, the Paragon DA-2 which provided the power to drive the loudspeaker. Up until the mid 1920s many people listened to radio using earphones, so most radios didn't come with speakers. Higher power tubes were required to drive loudspeakers. So many early radios did not have the output power to drive speakers, and manufacturers sold add-on amplifiers like this for customers who wanted to use them. Early radios required two sets of batteries (rear) to operate: the cylindrical "A" batteries (left) provided 3V to heat the filaments of the tubes, while the square "B" batteries (right) provided the higher anode ( plate) voltage for the tubes. Exhibit in the National Electronics Museum, 1745 West Nursery Road, Linthicum, Maryland, USA. All items in this museum are unclassified. The museum permitted photography without restriction.

Text of museum label card, right: "Paragon RA-10 radio receiver, 1920. Donated by John D. Crawford. Restored by Julius Kozma"