Found this on the net at this site (1 year old answer)
http://in.answers.yahoo.com/question/index?qid=2006092318111 9AA9jnPz
Television Rating Points - TRP is the criterion that indicates the popularity of a channel or programme and this data is very useful for the advertisers
Presently, INTAM (Indian Television Audience Measurement) is the only electronic rating agency functioning in India. INTAM uses two methodologies for calculating TRP. First is frequency monitoring, in which 'people meters' are installed in sample homes and these electronic gadgets continuously record data about the channel watched by the family members. 'People meter' is a costly equipment, which is imported from abroad. It reads the frequencies of channels, which are later, decoded into the name of the channels and the agency prepares a national data on the basis of its sample homes readings. But there is a drawback in the technique, as cable operators frequently change the frequencies of the different channels before sending signals to the homes. It may be very misleading to read a channel according to a particular frequency even if the down linking frequency is same all over India.
Second technique is more reliable and relatively new to India. In picture matching technique people meter continuously records a small portion of the picture that is being watched on that particular television set. Along with this agency also records all the channels' data in the form of small picture portion. Data collected from the sample homes is later on matched with the main data bank to interpret the channel name. And this way national rating is produced.
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