hi disha:-
QAM-based HD programming of local stations is sometimes available to analog cable subscribers, without paying the additional fees for a digital cable box. The availability of QAM HD programming is rarely described or publicized in cable company product literature.
QAM stands for "quadrature amplitude modulation," the format by which digital cable channels are encoded and transmitted via cable. QAM tuners can be likened to the cable equivalent of an ATSC tuner which is required to receive over-the-air (OTA) digital channels broadcast by local television stations; many new cable-ready digital televisions support both of these standards.
An integrated QAM tuner allows the free reception of unscrambled digital programming sent "in the clear" by cable providers, usually local broadcast stations or music. Which channels are scrambled varies greatly from location to location and can change over time; the majority of digital channels are scrambled because the providers consider them to be extra-cost options and not part of the "basic cable" package.[2]
In the United States a television that is labelled digital cable ready can have a CableCARD installed by the cable provider to unscramble the protected channels, allowing subscribers to tune all authorized digital channels without the use of a set-top box.[3]
Answered by
shepherd
, an ibibo Master,
at
6:24 PM on May 01, 2008