But given that mobile connections have long outnumbered fixed-line telephones and, because of their sheer convenience, cellphones have emerged as the most popular mode of communication, this is hardly an advantage. If the traditional system of tapping is ‘switch-based’, the new form is ‘off the air’. There are separate off-air monitoring systems for GSM and CDMA cellphones. Though they are designed to be mounted on a table or even fit into a bag, these high-tech gadgets are powerful enough to cover a whole city and track up to 1,000 simultaneous conversations. Despite their unimaginable potential for damage, they come relatively cheap with each set estimated to cost Rs 1-2 crore.

You don't hear much about this here ...