It's it the FTC not FCC. The Federal Trade Commission got involved just because of manufacturers were stretching the truth a little too much. If a receiver is rated as "FTC" it means all channels driven with a 20 to 20k Hz signal. Anything else is usually means a 1k Hz sine wave, or not all channels, or a combination.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris