Technical Notes:
Page 3

Since it did not matter what frequency these tubes rectified they could be used also for the rectification of high frequency. Thus the crystal detector with its instability became redundant. Unfortunately the sensitivity of the tube was much smaller compared to the crystal detector. Because this tube has only two elements: the heating and the positive plate, one calls it a diode.

Another word regarding heating: Initially the tubes were heated with direct current. As one tried to heat it with alternating current, could one state that the direct current , which drew from the anode a weak alternating current was modulated with the AC. This produced in the listener a weak, but unpleasant humming clay/tone. The solution lay in, that once the heater element was surrounded with a tube. The metal tube forms then the cathode. The electrons free up not from the heater element, but from this new cathode into the vacuum. This has still another further advantage: one applies on the cathode a layer, which consists of strong electron bearing materials, like the oxides of barium, strontium or thorium. Thus the current becomes stronger through the tube. We differentiate between these types by calling them directly and indirectly heated tubes.

To November 16, 1904 Sir Ambrose Fleming (1849 -1945) announces a patent on a diode and sends some samples to Guglielmo Marconi (1874 - 1934). He designs special receiver circuits for these diodes and equips some ship stations with good success.

Lee de Forest (Council Bluffs Iowa 1873 - 1961 Hollywood) Jan 29 1907 announces a patent for a three element tube (triode). He attaches a very fine wire mesh (grid) between the anode and cathode. If this grid is positively charged, then it strengthens the electron flow to the anode. If it is negative, then it decreases the flow.
Thus de Forest can regulate the electron flow nearly effortlessly. He calls his tube Audion. Thus the basic form of the radio tube was set. In English it is called a valve, in American a tube.

From now on many companies begin the building of tubes. Each company tries more or less to improve the tube design.TS This has the consequence that an enormous amount of patent disputes develop. Companies file bankruptcy, new companies develop. Mergers of companies begin and many companies begin to build tubes, and sell them to other companies under strange or double names. There are companies, which marked out their best quality tubes under their name, the second best quality tubes under another name and the rest under a third name.
Who actually makes the least amount of money, the technical designers and inventors.

When in 1960 the production of tubes (except large transmitting tubes) declined and the triumphant advance of the transistor began, so the situation fell out as follows: In America and Europe (except Russia, Japan, India) approximately 150 companies were formed and 21,550 different types of tubes were manufactured!

The large problem for our museum is:
How are we to some extent represent this tremendous variety to the visitor?
We decided to form three specialized groups: