USRobotics V.34 - Manual (Page 15)

COURIER HIGH SPEED MODEMS
Features and Compatibility 1-3
Flow Control/Variable Serial Port Rates
Flow control, required under error control, also allows the local
serial port (DTE) rate to be set higher than the link (connection)
rate, enabling greater efficiency and throughput. If your
equipment and software support high rates, data can be sent
from the computer to the modem at 115.2K, 57.6K, 38.4K or
19.2K bps, regardless of the link rate.
Voice/Data Switch
A switch on the modem's front panel allows you to change from
voice to data and back again, without issuing a command. See
Appendix G.
Stored Command String
If you don't ordinarily use voice and data in the same call, you
can assign the voice/data switch a different function that
normally requires a command, such as resetting the modem or
executing a stored command string. See
Voice/Data in Appendix
G for instructions on use of the voice/data switch.
Asynchronous/Synchronous Capability
Courier high speed modems operate synchronously as well as
asynchronously. A personal computer equipped with a
synchronous interface adapter can call computers that use
standard synchronous protocols. See Appendix F for more
information.
Synchronous Operations with V.25 bis
Used with computers that have a synchronous card and port,
Courier high speed modems combine the power of older
modems and automatic calling units in the mainframe
environment. They make synchronous connections by utilizing
V.25
bis, character-oriented (similar to BISYNC) and HDLC
protocols. See Appendix F for more information.
Dial Security
With Dial Security, you will be able to prevent unauthorized
access to a system with the use of Autopass, Prompting, and
Dialback. See Appendix D for more information.