Radio tube

One of the highlights in the early development of the radio tubes is this one, which contained a complete electronic circuit. This multiple electrode system contains three radio tubes and all the capacitors and resistors.
The top section of the radio tube is reflective due to the presence of magnesium. During manufacturing, the bulb is heated to draw a vacuum, and the last remaining gas binds to the magnesium. This results in magnesium deposits on the glass, causing the mirror effect. All the components are embedded in a separate covering of glass to ensure that the vacuum is maintained in the bulb. German manufacturer Loewe Radio produced this triple electron tube and was the only one to ever apply this technology.