A digital TV descrambler is a device, usually built into a set top box, that decodes encrypted channels and allows customers to watch subscription-based channels or pay-per-view events. Usually, the television service supplier will give subscribers a smartcard that allows the descrambler to work for the duration of their subscription. Some independent traders offer unofficial descramblers designed to allow viewers to watch subscription channels without paying, though this is both illegal and unreliable.
Descramblers can be used in both satellite and cable systems. In some countries, they are also used with digital terrestrial broadcasting: that is, digital channels broadcast over the air and received with a standard TV aerial. While some countries have all digital terrestrial broadcasts available without charge, other countries have systems where some premium channels are scrambled as with cable or satellite.
Consumers should not confuse a descrambler with a cable converter box. The latter device allows someone to watch the cable channel of his or her choice on a single channel on a TV. This can be done through a standard channel, such as the VHF channels on an American TV, or through the “auxiliary” or “external” channels assigned to RSA jacks or HD inputs. The confusion arises as most cable companies will build the descrambler directly into the converter box.
The name “digital TV descrambler” is also commonly used by people selling unofficial devices. These are billed as offering the chance to get access to scrambled channels, including those broadcasting pay-per-view events, without paying a subscription fee. Putting aside the fact that this is breaking the law, such offers are often not what they are cracked up to be. Digital channels are encrypted in a much more complicated manner today than in the analog TV era, lessening the chances that such devices will actually work. Even where a device does descramble channels when first used, there is absolutely no guarantee that it will continue to work permanently.
The legal situation over owning an unofficial descrambler has been a gray area. There is little, if any, dispute that possessing such a device is a criminal offense and that law authorities could prosecute owners. It is not clear whether TV service suppliers, such as cable firms, can take civil action over owners, however. A ruling in one case appeared to suggest that companies could only bring lawsuits where they had managed to obtain evidence that the owner had actually used the device.