Hi Weezer,
The bottom area is as it says the bit loading. I.e. the number of digital bits (1s or zeros) that the each tone or frequency holds.
The empty left-most section is the 3 kHz voice group, which is filtered out.
The low order group are the upstream group and the larger right hand are the downstream group.
The intervening group around Tone 32 is the empty gap to ensure there is a clean division between the two groups.
The tone numbers are at the very bottom, the next row of ones are just ruler markers and the row above are the total number of bits for each tone.
All the ones and blanks above just graphically represent the total transport area.
The higher tones won't support as many bits reliably and a few tones none at all.
Tone 64 is the unused pilot tone.
You'll see the loading pattern is identical to those DMT-software produced couloured pictures others use with different modems.
I hope this helps.
Kind regards,
Walter
