Hi all, I am happened to come across a project, which is really simple and got Rs. 75000(~$1700) as cash prize in a competition.

The concept is simple: Generally in landline phones, the number of rings can be used to convey some sort of info:

If two rings mean some info, if three rings mean another info, (if the callee understands).

Based upon this idea, a student has designed a project:

Both ends will have a 89C51, and DTMF dialer, LCD and Keyboard. You could type some 100 characters as sms, and give the destiation number in the node 1.

The MCU dials the destination, does some handshaking, and then conveys the ASCII as specific number of rings. The destination MCU 'understands' this, and decodes the SMS, displays on the LCD.

This system, even though terribly slow(atleast 3 mins for whole process), but completely free.

The project title:
"Free SMS using Landline phone to anywhere in the world"

He completely stole the show: He said, this system can be used anywhere in the world, since you are essentially dialling the destination number and cutting the call.

Also, after the initial handshaking, the destination MCU cuts the ringer of the telephone, so the callee wont be annoyed by the repeated calls.. There were more stories he told.

Interesting?

Regards,
Vignesh