Decatron

A thermionic valve is called a decatron that works as a pulse counter. Scheme of decatron

It consists of ten anodes that are the outputs of the tube. In addition, it has two groups of ten other anodes, those of each group interconnected with each other so that two pins, which are counting signals, are exited to the outside. By consecutively applying a positive pulse, the count is advanced or retracted. Functioning

The decatron contains low pressure gas, which ionizes when the anodes are at a sufficient positive voltage. This cloud of ionized gas creates a path of low resistance to one of the anodes. The tube remains in this state until a more positive pulse is applied to a counting electrode. At that time, the ionization moves to the nearest auxiliary anode (see figure). A second positive pulse on the other auxiliary anode advances the ionization. When the pulse disappears, the ionized cloud passes to the next anode, completing an account.

There are also models with a single set of auxiliary anodes that only allow the unidirectional count. In this type, it is the geometry of the tube that prevents the ionized cloud back to the anode where it left before the counting pulse.

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