User`s manual

U.S. Robotics I-modem Command Reference
Flow Control • Page 10-2
Hardware and Software Flow Control
Hardware Flow Control
I-modems implement hardware ßow control by detecting that a buffer is 90% full and then
interrupting the Clear to Send (CTS) signal to stop the ßow of data. When the buffer is
50% full, the I-modem sends CTS to restart the ßow of data.
Software Flow Control
I-modems implement software ßow control by detecting that a buffer is 90% full and then
sending special characters in the data stream to stop the ßow of data. When the buffer is
50% full, the I-modem sends special characters in the data stream to restart the ßow of
data.
The problem with software ßow control is that the characters used to stop (<Ctrl>Q) and
start (<Ctrl>S) the ßow of data can occur naturally in the data ßow. Enabling software
ßow control instructs the I-modem to recognize and act on these characters, even if they
are not intended to control the data ßow.
Using software ßow control may prove satisfactory if you're transferring text Þles only.