A "Strawberry Clock" ?
The IN-28 Strawberry Clock is an unique single-digit wall clock which displays time in sequences, 10's hours, 1's hours, 10's mins and 1's mins and simulates a 7-segment display with nine IN-28 "Nixie Dots" tubes. So far, kits for these tubes are not yet available on the market, especially since these tubes needs to be controlled as a Thyratron. So you'll get an unique piece of jewelery which also serves to "de-celerate" the everyday pace of life hectic as the time can not be read just with a glance.
The name "Strawberry" stems from the fact that in addition to the standard cover also face covers are offered with different colored mirrored acrylic glass and different motifs, including the strawberry as shown here.
But how can the clock display the time with only a single digit?
The clock displays the time in a sequence of four digits, each with a small pause between the individual numeral and a longer pause at the end of the sequence. It's really intuitive, and once you have understand the sequence, reading the time is very easy.
What are IN-28 Nixie-Dots ?
This tube was used earlier times in large size displays in Eastern European train stations. In addition to high brightness (influence of sunlight), it was also important to have simple control, high reliability and an extremely long service life - always with respect to the technology available 50 years before.
Therefore, the IN-28 was equipped with a "ignition electrode", like the gate of a Thyratron, the forerunner of today's Thyristor. Although the behavior of the IN-28 through this ignition electrode is similar to that of a switching tube (such as the small TX5-B Thyratron), the focus was more on brightness and easy driving than on the switching function.
The tube was in earlier times operated via a powerful series resistor to the unsmoothed bridge rectified mains voltage with an average current of up to 12 mA; by a burning voltage of 185 V this corresponds to 2.2 watts. At this power the tubes become fairly warm.
By choosing the "breakdown voltage" of 350 V, the tube does not ignite when the above-mentioned rectified full waves of the mains voltage is applied to the anode and cathode and the ignition electrode was not activated.
Only when about 170 V via a high-value resistor is applied to the gate, the glow discharge starts. And it persists, even if you take away the voltage from the gate.
You can only "extinguish" or switch off the tube if the voltage between the anode and cathode drops below the keep alive voltage. Therefore, a non-smoothed DC voltage was used in earlier days. The voltage zero crossings clears all tubes 100 times a second; and the tubes are ignited again when the voltage increases and if the necessary gate voltage is applied.