USRobotics V.34 user manual DB-25 DB-9 Pin Function

COURIER HIGH SPEED MODEMS

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.

B-4 Summaries and Tables