USRobotics V.34 - Manual (Page 98)

COURIER HIGH SPEED MODEMS
B-4 Summaries and Tables
Minimum Requirements
Some computer/terminal equipment supports only a few of the
RS-232 signal functions set in the Courier. The minimum
required for the modem to operate are as follows:
Asynchronous Calls
DB-25 DB-9
Pin Pin Function
2 3 Transmitted Data
3 2 Received Data
7 5 Signal Ground
20 4 Data Terminal Ready *
* Required only if you have the Data Terminal Ready
Operations switch OFF (DIP switch 1 OFF).
Synchronous Calls
You will need all of the above functions as well as pin 15 for
Transmitter timing signals, and pin 17 for Receiver timing
signals. You may need pin 24, which is assigned the external
timing source, rather than the internal (modem) source assigned
to pin 15. See Appendix F for more detailed information.
Additional Flow Control Functions
If your computer and software support Clear to Send and you
wish to use Transmit Data hardware flow control (&H1), Pin 5
(DB-25) or Pin 8 (DB-9) is required.
If your computer and software support Request to Send and
you wish to use Received Data hardware flow control (&R2),
Pin 4 (DB-25) or Pin 7 (DB-9) is required.
FOR 38.4K OR HIGHER SERIAL PORT RATE
Your terminal or computer and software must support the
115.2K, 57.6K, or 38.4K bps rate. Make sure the RS-232 cable is
shielded. Cables are normally six feet long, but longer lengths
are possible. If you encounter problems with signal
degradation, try a shorter cable.