By making one of the contacts transparent, the large area exposed emits light.Electroluminescent automotive instrument panel backlighting, with each gauge pointer also an individual light source, entered production on 1960 Chrysler and Imperial passenger cars, and was continued successfully on several Chrysler vehicles through 1967.
Electroluminescent panels are a capacitor where the dielectric between the outside plates is a phosphor that gives off photons when the capacitor is charged.
For line-voltage-operated devices, it may be supplied directly from the power line.
Electroluminescent nightlights operate in this fashion. Brightness per unit area increases with increased voltage and frequency.
For battery-operated devices, this voltage must be generated by a converter circuit within the device.
This converter often makes an audible whine or siren sound while the backlight is activated.