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USRobotics V.34 User Manual

Page 97

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COURIER HIGH SPEED MODEMS

Summaries and Tables B-3

PIN ASSIGNMENTS

The entire standard covers many more functions than are used
in most data communications applications. Pin assignments are
factory set in the Courier to match the standard DB-25 assign-
ments in the following table. DB-9 connectors for AT-
compatible computers should be wired at the computer end of
the cable as shown in the DB-9 column. If you're using an
Apple computer, we strongly recommend that you purchase a

Hardware Handshaking cable to get the highest possible reliability

performance.

Signal Flow

DB-25 DB-9 Circuit

Function

Computer

Modem

1

_

AA

Chassis Ground

both directions

2

3

BA

Transmitted Data

to modem

3

2

BB

Received Data

to computer

4

7

CA

Request to Send

to modem

5

8

CB

Clear to Send

to computer

6

6

CC

Data Set Ready

to computer

7

5

AB

Signal Ground

both directions

8

1

CF

Carrier Detect

to computer

12

_

SCF

Speed Indicate

to computer

15

_

DB

Synchronous TX* Timing

to computer

17

_

DD

Synchronous RX* Timing

to computer

20

4

CD

Data Terminal Ready

to modem

22

9

CE

Ring Indicate

to computer

24

_

DA

Synchronous TX* Timing

to modem

* Indicates Transmitter (TX) or Receiver (RX)

Table B.1

RS-232 Interface Pin Definitions