Batteryless radio

[1] The line-operated vacuum tube receiver was invented in 1925 by Edward S. Rogers, Sr.

He established the Toronto station CFRB (an abbreviation of Canada's First Rogers Batteryless) to promote sales of the product.

Sharp Electronics' first electrical product was a batteryless crystal radio introduced in 1925.

In this batteryless type of radio, the storage capacitors cache the electricity as static on layers of dielectric instead of chemical changes, providing energy like batteries do but 'batteryless'.

Storage capacitors recharge millions of times, they are relatively cheap, somewhat insensitive to temperature, and they never need replacing—which is why they are usually soldered on.

A simple circuit (very similar to a crystal set) rectifies the incoming signal and this DC current is then used to power a small transistor amplifier.