3Com Router 3000 Series Manual page 26

3Com Router Release Notes for V1.20
X.21 DCE Cable
The X.21 DCE cable has a DB15 (female) connector at the network end. Figure 12
illustrates the X.21 DCE cable.
Figure 12 X.21 DCE Cable
Table 17 lists the X.21 DCE cable pinouts.
Table 17 X.21 DCE Cable Pinouts
DB28 Signal
6 GND
9 MODE2
21 GND
13 RTS+
14 RTS-
23 CTS+
24 CTS -
19 RXD+
20 RXD-
1 TXD+
2 TXD -
15 TXCE+
16 TXCE -
Shielding shell Core-shielding
layer
Warning: To prevent damage to the router and ports, do not connect or
disconnect the interface cable to the 4-port synchronous/asynchronous serial
module with X.21 while the router is powered on.
Before connecting the 4-port synchronous/asynchronous serial module with X.21,
confirm the mode of the equipment that is connected to it (the synchronous/
asynchronous mode, DTE/DCE mode of the peer, and so on), the signaling
criterion required by the access equipment, baud rate, and synchronous clock.
To connect cables to the 4-port synchronous/asynchronous serial module with
X21:
1 Power off the router.
2 Verify the interface type of the peer device and choose the synchronous/
asynchronous serial interface cable of correct type.
Signal direction
<-->
<-->
->
->
<-
<-
<-
<-
->
->
->
->
<-->
26
DB15 (female) Signal
8 Circuit GND
1 Shield GND
5 Indication+
12 Indication -
3 Control+
10 Control -
2 Transmit+
9 Transmit +
4 Receiver+
11 Receiver -
6 Timing+
13 Timing -
Core-shielding Shielding shell
layer