COURIER HIGH SPEED MODEMS
The modem uses the U.S. Robotics proprietary HST cellular protocol to make connections. The call starts at 1200 bps, a V.42 error control connection is negotiated, then the modem switches to 4800 bps and begins measuring the line conditions. Depending on line conditions, the modem decreases or increases its connection rate, to a minimum speed of 300 bps and a maximum of 12K bps. If a connection terminates before data transfer is completed, the system tries to
If a large number of blocks are being resent (shown by the ARQ LED flashing randomly; some software displays the blocks retransmitted in the file transfer window), you may want to reduce the packet size by doing the following:
1.Be sure DIP switch 9 is ON so that the modem remains online if it receives +++.
2.If DIP switch 9 is OFF, switch it to ON and reset the modem by issuing the ATZ command.
3.Send the modem the escape sequence by typing +++ so that the transmission is interrupted, and wait 1 second.
4.Type AT S33=1 to reduce the packet size.
5.Then type ATO so that the modem returns online and continues to transmit.
NOTE: HST cellular connections can only be made with other U.S. Robotics modems in HST cellular mode. The modem cannot be used to place a voice or data call to another phone or modem when it is in this mode.
