4.4 Signal Poles
It is a device that indicates the status of the signal. The purpose of
signals poles to ON or OFF lights (Red, Yellow, and Green). Its
timing depends on the input given by the PLC according to the
timing of the programming priorities. One signal open at a time and
all other signals are stopped. Each signal light is a combination of
four LEDs, two are connected in series and two are connected in
parallel.