USRobotics V.34 User Manual
Page 97
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