Conditional access (CA) controls access to digital television (DTV) services via encrypting programs people watch. Its like the umpire in a ball game that calls your TV signal safe and lets you watch the show you want to see. There are various conditional access technologies, although they are all based on ATSC and DVB-compliant CA systems.

Conditional access has three basic elements: broadcast equipment, set-top box, and security module. The broadcast equipment generates encrypted programs transmitted to your television or cell phone.

The interactive TV set-top box filters your signals and passes them on to the security module. The security module authorizes these programs for decryption. The programs are decrypted in real time and sent back to the set-top box for display. It's like at the ball game, the pitcher looks at the catcher, the catcher at the batter, the batter at the third base coach and the third base coach at the bat boy. If every one's set, he pitches the ball.

Subscriber Management System (SMS) - Interactive TV The brains of Interactive TV are in the Set-top box on top of your TV set. Your subscriber management system requests the permission to provide the authorization needed to view the programs. Other systems acts as a backup system in case your left stranded on third base..

Subscriber Authorization System (SAS) - Interactive TV The clean up hitter in your access system responsible, waves your signal so you can watch the ball game on TV with your kids. There is also has a security module so you can keep your kids from watching gulls mate and people from charging their TV shows to your account. The Interactive TV wizards thought of everything... they even built a converter to watch digital signal on your old TV set the one had since your team won the World Series twenty five years ago.

Amazing technologies like Interactive TV are costly to develop, operate and upgrade. With out conditional access, the only way many people would see their favorite team is out at the ball park. Also, Believe it or not, many people go to the ball game and watch replays on cell phones powered by Hey, I think he just hit a home run!