The Indian DTH licence specifically spells out that DTH Set Top Boxes (STBs) must be based on an open standard so that the same box, purchased by a subscriber, would work across different DTH service providers such as Tata-Sky and Dish TV.
However, each service provider deploys their own unique CAS (Conditional Access System) which authorises subscribers to view only those channels for which they have paid. Each CAS system is unique and forms an integral part of the secure channel delivery versus payment system.
Therefore to enable the same box to work across different CAS systems, each box must have a slot to accept a third party's Conditional Access Module.
As a practical example, Dish TV utilises Conax's Conditional Access System while Tata-Sky deploys NDS.
If a Dish TV DTH STB is to be used for receiving Tata-Sky signals, the Dish TV STB must have the facility to attach an external, NDS Conditional Access Module (CAM Module). Further, Tata-Sky must provide NDS CAM modules on demand to customers of Dish TV who want to switch to TataSky.
Today unfortunately for the consumer neither DishTV, Tata-Sky or Sun TV provide CAM modules for use with another platform's STBs. This could be perceived by consumers as a Monopolistic & Restrictive Trade Practice, and should also be challenged under MRTP provisions.
ROFL..... yeah right.... you go ahead and challenge that.