Page "Set-top box" Paragraph 7

These frequencies corresponded to non-television services ( such as two-way radio ) over-the-air and were therefore not on standard TV receivers.

Before cable-ready TV sets became common in the late 1980s, an electronic tuning device called a cable converter box was needed to receive the additional analog cable TV channels and transpose or convert the selected channel to analog radio frequency ( RF ) for viewing on a regular TV set on a single channel, usually VHF channel 3 or 4.

The box allowed a non-cable-ready television set to receive cable channels, and often provided a wired or wireless remote control.

While later televisions were cable-ready with a standard converter built-in, the existence of premium television ( aka pay per view ) and the advent of digital cable have continued the need for various forms of these devices for cable television reception.

Block conversion of the entire affected frequency band onto UHF, while less common, was used by some models to provide full VCR compatibility and the ability to drive multiple TV sets, albeit with a somewhat nonstandard channel numbering scheme.