Cisco CPA2501 User Manual page 28

Preparing to Connect to a Network
Figure 2-4
X.21 Connections
The X.21 connector uses a 15-pin connector for balanced circuits and is commonly used in
the United Kingdom to connect to the public data network. X.21 relocates some of the logic
functions to the DTE and DCE interfaces and, as a result, requires fewer circuits and a
smaller connector than EIA/TIA-232.
The network end of the X.21 serial transition cable (not included) is a standard DB-15
connector, as shown in Figure 2-5. The end that connects to the serial port on the rear panel
of the router has a DB-60 connector. X.21 cables are available with a plug or receptacle in
either DTE or DCE mode. To order a cable, refer to the section "Obtaining Service and
Support" in the "Overview of the Router" chapter.
Figure 2-5
8
15
2-14 Router Installation and Configuration Guide
V.35 Serial Transition Cable Connectors, Network End
DTE
DCE
X.21 Serial Transition Cable Connectors, Network End
1
9
DTE
DCE