In the 1030 Modem Owner's Guide Atari states (page 7; pdf page 9):
If you have an Atari 400 Home Computer, you cannot use the tone (push-button) dialing feature to dial from your computer's keyboard.
What is unique about the 400 to result in this limitation?
Since I understand that POKEY generates the tones for tone dialing for the 1030, does this reflect something unique about the way POKEY is connected in the 400?
Related question is, does POKEY generate the dial tones for the 1030 in a similar way to its generation of the Mark and Space tones for recording to cassette? That is, using two-tone mode to produce sound over SIO serial data out pin 5?
I barely grasp how two-tone mode for cassette recording works as it is, and now I'm further trying to understand how two-tone mode would be applied to generating a full set of dial tones.