User`s manual

U.S. Robotics I-modem Command Reference
Flow Control • Page 10-5
Keep in mind that the XON/XOFF characters sent to the remote computer
may interfere with XON/XOFF signaling between the remote computer
and remote device. See &I2.
&I2 The I-modem acts on your XON/XOFF commands, but removes them from
the data stream instead of passing them to the remote computer.
This ensures that the remote computer does not confuse your XON/XOFF
characters with those from its attached device. This is the recommended
setting for ARQ mode.
Note If the call is not in ARQ mode, there is no ßow control on the link. If you
send an XOFF to your modem and it stops passing data, it has no way to
tell the remote computer and modem to stop sending for a while, and the
I-modemÕs buffer may overßow. For more reliable control in non ARQ
mode, see &I5.
&I3 Hewlett PackardÐHost mode. Applies only to I-modems attached to an HP
mainframe that uses the ENQ/ACK proto-col. Use in ARQ mode only.