For panel and signal decoder, LED drivers are used. These LED drivers get their power (5 volt) from the serial cable connecting them.

Long cables, many connectors, or power hungry LEDs, can cause voltage drop on the cable.
If the voltage drops too low, this can cause some LEDs to flicker, or some LEDs may not work at all.

This card can be used to feed the serial cable at more places along the cable to keep the voltage at an acceptable level.

If LEDs are off or flickering at the end at the serial cable, this card can be placed at the end.
In many cases it is enough to add the card without connecting any power, as the on board capacitance will stabilize power.
If more power is needed, a 5 volt power supply should be connected to the terminals on the board.

Size of the card is 35*20mm.