DH> telephone company has done a lot of research with this since the smaller
 DH> the bandwidth allocated to your voice, the more channels they can cram
 DH> into one line.
 DH> With voice, this would only need to be 7KHz and eight-bit sampling
 DH> would probably be just fine.  This would run into the 70,000
 DH> bits-per-second range - well within serial port capability.
FYI, a standard B channel or equivalent (1/24th T carrier, etc.) is 8 bits at 
8 ksps, with one bit sometimes stolen for sync in some channels.  
For modem operation, it's impossible to compand that without problems.  Some 
PBXs and other gear do use 1/4 DS-0 16 kbps allocations for voice channels, 
to the greater detriment of modem data than voice.  
2 bit 8 ksps adaptive-predictive delta mod voice sounds better than many old 
POTS lines, especially if compared via a bridged pair of long (thousand miles 
each) loops.  
Terry
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