The central concept of CAS is the ability of the cable operator to remotely manage channel access to a subscriber.

At the heart of the system lies:

1) The Set-top box (STB) each of which has a unique ID#. Each STB is equipped with a data receiver and microprocessor. Data streams generated at the cable operator headend are received by the STB which receives both scrambled (Pay) and unscrambled (FTA) channels. The microprocessor compares the ID assigned to the box to the ID sent by the data stream. When the ID #s match, it starts processing the information received – for instance, if the STB is tuned to a channel that has an authorisation tag, it decodes it and the home can then view the channel. The head-end, here, does not need to receive any authorisation or confirmation signal back from the set-top boxes.

2) The Subscriber Management System (SMS) manages the subscription details. The SMS software generates subscriber-wise details on channels subscribed to and in effect authorises or deauthorises each customer's set-top box (STB).

Since the whole concept is that of remotely controlling access, there is no need of the physical presence of the cable operator to turn on or off a channel – this is something very important to understand since there is a misconception that visits by the cable operator will be very frequent. While initially this may be true to sort out hardware problems, once the system stabilizes, visits by the local operator are restricted to collecting the monthly subscription

Q.2 Does everyone have to buy a set-top box (STB) to view C&S channels?

No. A home needs an STB only to watch pay channels. It can continue to watch free-to-air (FTA) channels without the STB with the regular C&S connection.

Q.3 Is it possible for a home to continue to receive pay channels without the STB?

On implementation of CAS, by law, any cable operator delivering a pay channel through a non-addressable system, will be jailed. Having said that in countries where addressable systems exist, there are individuals engaged in ‘hacking’ who continue to watch channels without paying for them - illegally of course.

Q.4 What are the areas that come under the ambit of CAS?

Chennai is already a CAS Market. The Southern parts of Delhi & Mumbai (as defined by Census) and the MC portion of Kolkata would come under the ambit of CAS, to begin with.