dtmf tuning?

Does anyone on the list know why dtmf signals
(as used on touch tone phones) are tuned to
the following pairs of frequencies?

Digit: dtmf freq. pairs approximate pitch (equal temp.)
1: 1209Hz 697Hz D#6 1244.508Hz F5 698.456Hz
2: 1336Hz 697Hz F6 1396.913Hz F5 698.456Hz
3: 1477Hz 697Hz F#6 1479.968Hz F5 698.456Hz
A: 1633Hz 697Hz G#6 1661.219Hz F5 698.456Hz
4: 1209Hz 770Hz D#6 1244.508Hz G5 783.991Hz
5: 1336Hz 770Hz F6 1396.913Hz G5 783.991Hz
6: 1477Hz 770Hz F#6 1479.968Hz G5 783.991Hz
B: 1633Hz 770Hz G#6 1661.219Hz G5 783.991Hz
7: 1209Hz 852Hz D#6 1244.508Hz G#5 830.609Hz
8: 1336Hz 852Hz F6 1396.913Hz G#5 830.609Hz
9: 1477Hz 852Hz F#6 1479.968Hz G#5 830.609Hz
C: 1633Hz 852Hz G#6 1661.219Hz G#5 830.609Hz
*: 1209Hz 941Hz D#6 1244.508Hz A#5 932.328Hz
0: 1336Hz 941Hz F6 1396.913Hz A#5 932.328Hz
#: 1477Hz 941Hz F#6 1479.968Hz A#5 932.328Hz
D: 1633Hz 941Hz G#6 1661.219Hz A#5 932.328Hz

Do they correspond to a particular tuning system or internal
relationship?

Does the tuning have specific relationship to the way the dtmf system
works (I'm guessing it does)

Many Thanks,

Jon Drummond