USRobotics V.34 - Manual (Page 190)

COURIER HIGH SPEED MODEMS
G-8 Additional Operations
HEWLETT PACKARD INSTALLATIONS
During error control connections, the Courier recognizes the
ASCII ENQ/ACK characters exchanged between many Hewlett
Packard host computers and their terminals. The HP host sends
the terminal an ENQ character at predefined intervals, and
sends no more data until the terminal responds with an ACK
character.
Courier modems manage this ENQ/ACK protocol so that
communication is speeded up, thereby enabling HP terminals to
achieve high speeds on dial-up lines. Special flow control
settings, using the &I command, are required for HP users.
These settings apply to ARQ connections only and to Courier
modems set to either B0 or B1. Disregard other Courier flow
control commands.
Set the Courier to Host mode if it is attached to the host
computer, or to Terminal mode if it is attached to a terminal, as
follows:
Host mode
AT&I3 <Enter>
Terminal mode
AT&I4 <Enter>