The underground stations are known to be narrow, long and with low lighting.
Here the teleindicators must generate their own light, but without dazzling viewers. Consequently an adecuate solution is the use of LEDs.
Usually we will opt for a tricolor matrix LED technology, which allows the construction of graphic panels.
These graphic panels can show the information in green, yellow and red.
The use of a matrix technology simplifies the electronics because LEDs placed in the same matrix share the same lines of control.
To simplify the electronics is synonymous of a moderate fabrication cost. Inside the matrix LED groups there are different tonalities and luminosity.
We use LED matrices with transparent resins which we complement with an ochre sandblasted methacrylate panel. Optionally it can be polycarbonate.
They differ from the ones above in that they are normaly outside, which implies high luminosity during the day and low during the night.
In this case the matrix technology must not be used. Instead LEDs must be mounted individually. This requires more complex electronics, because you need to control each LED individually and have a self-regulating light system.
We normally use 3 mm LEDs with a 120º angle and a separation of 10 mm between centers. Also oval LEDs separated 15 mm.
Our electronics regulate the light intensity of each LED, adjusting the temperature. The end result is that all LEDs in the same panel have the same brightness in spite of the small divergences from one LED to another.