On Sun 11 Aug at 11:27 Ludi Desouza (3:711/413) wrote to Bill Grimsley:

 LD>     USR chooses the 3200 symbol rate when answering a call 
 LD> from a modem that doesn't support the 2743 symbol rate and 
 LD> that indicates the same maximum projected data rate for both 
 LD> the 3200 and 3429 symbol rates.  This does not match what 
 LD> some other V.34 implementations do.  By choosing the 3200 
 LD> symbol rate instead of the 3429 symbol rate they are giving 
 LD> up about 2dB of SNR.  
 LD>  
 LD> ...
 LD>  
 LD>     As I stated in my last email I suspect USR chooses the 
 LD> 3200 symbol rate in order to avoid problems with very old 
 LD> Rockwell products.  This problem was fixed well over a year 
 LD> ago.  I can't blame USR for making the choice they did since 
 LD> there are a lot of modems that still have the problem. 

It gets worse. USR made a bad design decision with their V.34 Couriers
failing to detect the rapid channel roll-off when going through 3 64 kbps
PCM stages, trying for the 24000 bps at the 3429 symbol rate, when the link
can only sustain error-free operation at 19200 bps.

Also, when forcing 2400 bps, a USR will still try the 3429, 3200, ????
symbol rates before using 2400 symbols per second which is the only symbol
rate that supports 2400 bps anyway.

/-:.

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