Sidecar - This type of set-top box provides an additional transport stream of data from the content provider (network operator) to compliment the original stream going to the set-top box.  With Charter Communications’ interactive TV rollout, the BMC-8000 (Broadband Media Center) is/was a sidecar box that works/worked in tandem with the Motorola DCT-2000 set-top box. A fully integrated set-top box would not require a sidecar. (This is a 2003 definition and may be antiquated.)
ASTB (Advanced Set Top Box)

Black Box

Converter

Descrambler (De-scrambler)

Detailed explanation of Set top Boxes

Digital Satellite System, Satellite Box

Digital Set-top Box

Intelligent Set-top Boxes

Interactive TV Software

IP-based Set-top Box

Set-top Box-based Banking

Set-top Box & Integrated TV Manufacturers & Developers

Set-top Box Software

Set-top Box Subscriber

Smart TV Set-top Box

Venus Set-top Box Project

Video Juke Box – (Digital Video Music)