set-top box (redirected from Set-top unit)

set-top box

The cable TV box. Although impossible to rest on "top" of a flat panel TV set and often located several feet from the TV no matter what type is used, the set-top box (STB) term comes from the early days when cable boxes usually rested on top of CRT-based TVs. Satellite TV uses a similar device; however, rather than a "satellite set-top box," it is officially known as a "satellite TV receiver."

For analog service, set-top boxes descramble the premium channels and manage the higher channel numbers old TVs do not support. For digital service, they decode the MPEG-based digital signals, decrypt the premium channels and store and display the program guides with the channel numbers assigned by the cable provider. "HD set-top boxes" offer high-definition signals in addition to standard definition (SD). See HDTV and MPEG.

Built-In DVR
A digital set-top box may have a built-in hard drive for pausing, rewinding, recording and playing back TV programs. Stand-alone DVRs, such as the HD models from Tivo, perform the digital decrypting and decoding with plug-in CableCARD modules that move the cable company algorithms from the set-top box into their units. See CableCARD and DVR.

Internet Access
Although most cable companies offer TV and Internet service, the traditional set-top box does not provide Internet access. Where it enters the house, the cable is divided into two by a small, passive device called a "splitter." One line goes to the set-top box, and the other is fed to the cable modem. See hybrid set-top box and cable modem.

---

(communications, networking)

set-top box - (STB) Any electronic device designed to produce output on a conventional televesion set (on top of which it nominally sits) and connected to some other communications channels such as telephone, ISDN, optical fibre or cable. The STB usually runs software to allow the user to interact with the programmes shown on the television in some way. Online Media are one STB manufacturer.