US Robotics 005689-03 Manual page 49

Register Default
S9 6
S10 7
S11 70
S12 50
50
Function
Sets the required duration, in tenths of a second, of the remote modem's carrier signal
before recognition by the Sportster.
Sets the duration, in tenths of a second, that the modem waits to hang up after loss of
carrier. This guard time allows the modem to distinguish between a line disturbance from
a true disconnect (hang up) by the remote modem.
While we don't recommend connecting the modem to a line with call waiting, if you have
it, you may wish to adjust this setting upward to prevent the modem from misinterpreting
the second call signal as a disconnect by the remote modem.
A better alternative is to ask your phone company how to temporarily disable call waiting
(usually *70W). For example: ATDT *70W phone number.
Note: If you set S10 = 255, the modem will not hang up when carrier is lost. Dropping
DTR hangs up the modem.
Sets the duration and spacing, in milliseconds, for tone dialing.
Sets the duration, in fiftieths of a second, of the guard time for the escape code sequence
(+++).