Vacuum fluorescent display (ger. Digitron Fluoreszenzanzeige) - vacuum tube, display element, working on the principle of an electron tube.

Vacuum fluorescent tube is a directly heated triode electric vacuum with a plurality of phosphor coated anodes. Parameters of the tube are chosen so that it could operate at low anode voltages - from 9 to 27V. Represents a direct heating cathode of tungsten with 2% thorium to facilitate emission at a relatively small temperature. Depending on the height of the indicator is used either one or several parallel-connected filaments in diameter than a human hair. For a small applied tension of flat springs. Filament voltage , depending on the length of the indicator is between 0.8 and 5V. If it is unknown, in complete darkness gradually increase the heater voltage from zero until a faint red glow. It is at this temperature thread it can not burn out very long . At a higher voltage when the cathode glow shows clearly increases the risk of burnout. Warming takes a split second and sometimes accompanied by a characteristic acoustic "ringing" due to thermal deformations .

In contrast to the grid receiving-amplifying vacuum tubes that are cylindrical, their grid - flat. Number of grids usually equal to the number of familiarity indicator. Appointment grids - is twofold: first, they reduce the voltage sufficient to light shone brightly, and secondly, allow switching bits with dynamic display . Phosphor coated anodes with a small excitation energy of only a few electron volts. This fact allows the tube to operate at low anode voltage, as well phosphor is excited by low energy electrons. Segments are lit and illuminated with black light, the photon energy at which the wavelength of 380nm.

In the Soviet Union for the first time been applied to VFD calculator EKVM "24-71". This calculator is a functional copy of a similar Japanese model QT-8D. In 1971 the factory "Reflector" indicators released by the deadline, which later became known as IV-1 and IV-2.

In the USSR, the indicators produced by enterprises:

• Saratov factory "Reflector";
• "ORZEP" Orel plant electronic devices;
• Leningrad Association "Svetlana";
• Dyatkovsky plant "Anode".

Vacuum Fluorescent indicators produced in the USSR, East Germany and Japan. At the moment they are made in Japan, and a small amount produced in Russia.