Dear Prahlad,

The 433MHz is a very popular band when it comes to short range industrial remote controls. They are mostly used as the carriers in the RF units for overhead cranes and other such equipments where the operator has to be within a few meters of the equipment that he is controlling.

I am not sure if in India we have something that is the equivalent of FCC as in the US - in any case there are two main criteria with respect to the frequency allocation - one is the frequency band and the other is the power of transmission ( Correct me if I am wrong ). I have in fact completed two remote controlled equipments with the 433MHz band and its almost three years they are in operation and I am not behind bars!.. I tried my best to get some inputs on the legality of the bands - but failing in the effort , just went ahead and used RF modules that had FCC certification.

If you talking of using this for communication within a radius of 10 to 20 meters - I am sure you are "safe" to use one of the modules that confirms to the FCC or equivalent guidelines.

Another idea would be to contact any ham radio operators in your area - after all having passed certificate exams in this frequency allocation stuff - he/she should atleast be aware of this.

Raghu