3Com U.S. Robotics 56K Voice User Manual page 68

&Un Sets floor connect speed when set above 0, if the
connection cannot be established above this speed, the
modem will hang up. When &Un is used in conjunction with
&Nn and &Nn is greater than 0, &Nn is the ceiling connect
speed.
&N=0
&U=0 Connects at best
possible speed
between your modem
and the remote modem
Note: These factory
default settings should
be sufficient for most users.
&U>0 Connects at any speed
faster than the value of &Un
&U0
connection
&U1 300 bps
&U2 1200 bps
&U3 2400 bps
&U4 4800 bps
&U5 7200 bps
&U6 9600 bps
&U7 12,000 bps
&U8 14,400 bps
&U9 16,800 bps
&U10 19,200 bps
&U11 21,600 bps
&U12 24,000 bps
&U13 26,400 bps
&U14 28,800 bps
&U15 31,200 bps
&U16 33,600 bps
&U17 28000 bps
&U18 29333 bps
&U19 30666 bps
&U20 32000 bps
&U21 33,333 bps
62 56K Voice Faxmodem Internal - User's Guide
Technical Reference
No restrictions on the minimum speed for the
&N>0
Connects at speed
defined by &Nn. If the
connection cannot be
made above this speed,
the modem will
hang up.
Connects at any speed
between &Nn. and &Un