Um, yes, there is a carrier wave. (A baseband carrier wave). It is modulated at the signal frequency (the baud rate). If you turn the speaker on, you can hear the carrier wave, and the modulation. For V21 (asynchronous transmission at rates up to 300 baud), the carriers were 1080 Hz and 1750 Hz. Bell 103 used a similar system, but it was normally quoted giving the min/max frequencies, rather than the carrier frequency: conceptually, you could think of it as modulating 4 frequencies, rather than 2.