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As you unmindfully wait for the light to turn green, the good old wireless
technology, ensures news capsules flitting across the mounted Light Emitting
Diode (LED) boards, bringing you your instant news digest.
The system works on any of these three technologies:
 GSM
data services: Though old and less sophisticated, it is presently the most
widespread. This requires a GSM modem attached to a computer at the owner's
site, which connects with the GSM modem inside an LED board, mounted atop the
traffic signal, and transfers the data. This data then passes through the
operator. While the modem inside the board downloads the data, it still has to
be displayed in a specific format like scrolling, blinking, flashing, etc. This
job is done by the micro controller (MC, inside the LED board).
 SMS
based: This system requires a software application, inside the computer at the
owner's site. However, a GSM modem and an MC are required inside the board.
The software sends the data in the form of an SMS, over the internet, to the
middleware, which does the password and authentication check. The data then
passes through the operator and is downloaded by the modem inside the board and
displayed by the MC. This system is more secure as it allows only the authorized
users to send the data.
 GPRS
based: It uses the GPRS technology instead of GSM, the functioning being the
same as the SMS system. The key difference here is that GPRS, being always on,
the data can be changed and updated every moment. This makes it ideal for
displaying very dynamic information like stock quotes.
 Power
supply
The power system is very critical. There are two power lines connected to
each of the boards-one to the modem and the other to the LED display. The
power line to the display gets tripped, as soon as the light turns green at the
signal, with the one to the modem remaining on. This avoids distraction. The
power line to the modem is however not switched off as it takes time for the
system to reboot, which will make it difficult to be ready to display the
messages by the time the signal goes red again.
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