An RF modulator is a handy little gadget that's necessary for most people's home theater systems, especially if this system has an older television. It converts the component signal (usually carried by three RCA cables), into a signal that is "patched in" over either channel 3 or 4 on your cable or antenna cord.

This is because while your cable or antenna cord carries multiple channels on several frequencies, your A/V component (your Playstations and DVD players and such) outputs three individual signals--
  • yellow: Video
  • red: Right-speaker audio
  • white: Left-speaker audio
The RF modulator combines these three signals and substitutes them as a pseudo-channel on your cable/antenna line--usually channel 3 or channel 4. Newer models will auto-detect a signal and substitute when the A/V component is turned on, while older models may require some sort of manual switching.

You can buy them at your friendly local Radio Shack for about $30.

There are also specialized, less-expensive versions of RF modulators made for gaming systems that bypass the A/V cables altogether. These vary in price from $10-$20.