TVGuardian must sit between the source (a tuner) and your TV to be able to read the closed-captions and intercept the audio before you hear it.
Standard Definition TV: You must have a cable, satellite or IPTV box. A VCR will work with cable instead of a cable box. TVGuardian will be connected between one of these items and your TV using two composite (Red/White/Yellow) cables.
Over-The-Air TV: You can use TVGuardian with over the air TV, however, you need an external ATSC tuner or a Tivo DVR. For standard definition TVs, you will need a DTV converter box.
Here are some links to explore. We have not been able to test the products in the links, but the should work with TVG.
http://www.firebird-systems.com/graphics/dct210/digital-tv-tuner-hdmi-dct210.shtml